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Plants belonging to the Rhododendron subgenera Pentanthera (deciduous) and Tsutsusi and Azaleastrum (evergreen) are called azaleas. Azalea belongs to family Ericaceae. Azaleas are one of the favourite ornamental plants used by home owners and professional landscapers. They are used as foundation, accent, individual specimen plants, and as mass plantings. Azaleas are good companion plants, working well in designs with many trees, shrubs and ground covers, offering a variety of landscape options. Azaleas can be found in all ranges of colours, from delicately pink-tinged white to strong, bright red, and there are species that has the startling colour of flame. Its bold colour scheme has caused people to carry it far and wide, for use wherever a sudden note in strong hue is appropriate among the milder expressions of the rest of the flowers. The evergreen azalea, Rhododendron simsii Planch., is one of the most important pot plants in Western Europe and the USA. The breeding history of this vegetatively propagated plant is a relatively short one, and breeding has been focused on flower characters because the public is continually asking for new flower colours and flower types.

ORIGIN AND DISTRIBUTION

Nevertheless, very little was known about the origin and the ancestor species used for this important ornamental crop. Rhododendron simsii, the species that is accepted to be the main ancestor, originates from hilly areas in China (Chang Jiang valley), Thailand, Laos and Burma. Apart from R. simsii, at least three other species from the Tsutsusi subgenus, from South-Asia and Japan, might have contributed: R. indicum, R. x mucronatum (Blume) G. Don and R. scabrum (Heursel, 1999).

From a floricultural viewpoint, azaleas are firstly divided into the two broad categories of deciduous and evergreen plants. The former, notoriously more rustic, have North American, Caucasian, and Asian origins, and are classified in the subgenus Pentanthera G. Don, whereas the latter derive exclusively from Asian species and are classified in the subgenus Tsutsusi (Sweet) Pojarkova (Chamberlain and Rae, 1990). Within the evergreen azaleas at least four more or less well defined groups of cultivars are distinguished according to their traditionally recognized most important ancestor: pot or Belgian azaleas (R. simsii Planch. putative hybrids), Hirado azaleas (R. scabrum G. Don putative hybrids), Kurume azaleas [putative hybrids of R. kiusianum Makino var. kiusianum and var. sataense (Nakai) D.F. Chamb. and R. kaempferi Planch.] and Satsuki azaleas [putative mutants or hybrids of R. indicum (L.) Sweet and R. eriocarpum (Hayata) Nakai]. The Hirado, Kurume and Satsuki groups are often referred to as Japanese azaleas because of their geographical origin (Scariot et al., 2007).

Bougainvilleas (Bougainvillea spp.) are tropical and sub tropical plants belonging to Nyctaginaceae family. They are thorny, evergreen and some are fragrant. Bougainvillea is named for “Louis A. de Bougainville”, a French navigator (1729-1811) who discovered the plant in Brazil in 1768. Bougainvillea plant spreading horizontally or hanging downwards as it is climbing upwards, it makes itself at home in almost any situation. It can be grown as a hedge, groomed as a ground cover, pruned as an espalier, trained as a tree or contained in a pot in a variety of shapes. Bougainvillea is ideal for bonsai. Red, violet, orange, yellow or white bracts appear at the ends of new growth.

ORIGIN AND DISTRIBUTION

Bougainvillea is a native of South America (Bailey, 1963, Menninger, 1970 and Hackett and Sachs, 1985) from Brazil west to Peru and south to southern Argentina. A French explorer and naturalist, Dr. Philibert Commerson or Commercon (1727-1773), discovered the bougainvillea in Rio de Janeiro in 1768. He may have been traveling on a supply ship at the time. His discovery would soon find a name and go on to make a name for itself all over the world. In 1766, a ship called La Boudeuse set sail from Nantes on a round-the-world voyage of discovery commissioned by the French government. At the helm was Louis-Antoine de Bougainville (1729-1811), a mathematician and an admiral in the French navy. When La Boudeuse arrived in Rio de Janeiro to rendezvous with the supply ship, the occasion made horticultural history. Commerson’s newly discovered plant received a name, bougainvillea, in honour of the admiral.

Twenty years after Commerçon’s discovery, it was first published as ‘Buginvillea’ in Genera Plantarum by A.L. de Jusseau in 1789. The genus was subsequently spelled in several ways until it was finally corrected to ‘Bougainvillea’ in the Index Kewensis in the 1930s. Originally, B. spectabilis and B. glabra were hardly differentiated until the mid-1980s when botanists recognized them to be totally distinct species. In the early 19^th century, these two species were the first to be introduced into Europe and soon, nurseries in France and England did a thriving trade providing specimens to Australia and other far away countries. Meanwhile, Kew Gardens distributed plants it had propagated to British colonies throughout the world. Soon thereafter, an important event in the history of bougainvillea took place with the discovery of a crimson specimen in Cartagena, Colombia, by Mrs. R.V. Butt. Originally thought to be a distinct species, it was named B. buttiana in her honour. However, it was later discovered to be a natural hybrid of a variety of B. glabra and possibly B. peruviana - a “local pink bougainvillea” from Peru. Natural hybrids were soon found to be common occurrences all over the world. For instance, around the 1930s, when the three species were grown together, many hybrid crosses were created almost spontaneously in East Africa, India, the Canary Islands, Australia, North America and the Philippines.

The Camellia is one of our most beautiful and most appreciated ornamental plants belonging to the family Theaceae. The genus Camellia was named by Linnaeus after the Jesuit botanist “Georg Joseph Kamel”. Camellias represent gratitude, love and perfection and are a perfect way to tell someone they possess those qualities. The camellia is the state flower of Alabama. Industrial use of Camellia is in the oil industry. Seeds of several species belonging to the sections Oleifera, Paracamellia, Camellia and Furfuracea are used for extracting edible oil, which is used extensively for cooking in China (Ming, 2000, Gao et al., 2005 and Zhang et al., 2007). In China, more than 3 million hectares are used for camellia oil production and nearly 645000 tons of seeds are harvested each year, which yield nearly 164000 tons of edible oil (Ming, 2000 and Gao et al., 2005).

ORIGIN AND DISTRIBUTION

Since it is a native of warm temperate regions (southern China) and thrive throughout a wide area extending from Washinton, D.C., south through Georgia and Florida, west along the Gulf Coast and north along the Pacific Coast as far as Seattle. Species of Camellia are largely distributed in south-eastern and eastern Asia and China, which, being the centre of species diversity, possess more than 80% of the species (Gao et al., 2005).

Diploid Camellia reticulata was discovered in the Jinshajiang valley, Yunnan and Sichuan provinces, China, at an elevation of 1650-2800 m and under high humidity conditions (Xia et al., 1994). Yunnan province is the centre of origin for C. reticulata (Xia et al., 1994). The most important ornamental species is C. japonica L., of which there are over 32000 registered cultivars (Savige, 1993). Today, plants from C. japonica, C. reticulata, C. sasanqua and a group of yellow-flowering species called golden camellias are grown as ornamental plants worldwide. The family can be divided into three groups of similar genera (Prince and Parks, 2002).

Lagerstroemia indica belongs to family Lythraceae commoly known as Crape myrtle. It it grown well in India for various landscape purposes. It is called Sawani or Shravani (Hindi), Dhayti (Marathi), Chinagoranta (Telugu), Pavalakkurinji (Tamil). Lagerstroemia a long period of striking rainy season flower colour, attractive fall foliage and good drought-tolerance all combine to make a favourite shrub or small tree for either formal or informal landscapes. It is a deciduous, multi stemmed; rounded crown; dense branching and is highly recommended for planting in urban and suburban areas.

The scientific name, Lagerstroemia, was coined in 1759 by Carl Linnaeus, who described and named the plant in honour of “Magnus von Lagerstroem”, an avid naturalist and director of the Swedish East Indies Company. Crape myrtle derives its common name from its crepe-like, crinkled petals, and the resemblance of its leaves to the true myrtle, Myrtus communis. “Crape myrtle” is a peculiarly-American term. Elsewhere in the world, “Lagerstroemia” is often used as the common name for crape myrtle (Knox, 2003).

Crape myrtle is the smaller version of Lagerstroemia speciosa, commonly known as Pride of India or Queen crape myrtle. The deciduous crape myrtle is among the longest blooming trees in existence with flowering periods lasting from 60-120 days. Crapes come in heights as short as 46 cm and as tall as 12 m. Leaves are alternate and smooth, but leaf size depends on variety. Flowers are borne in summer in big showy clusters and come in white and many shades of pink, purple, lavender and red. The bark is a prominent feature being smooth, pinkinsh-gray and mottled, shedding each year. Leaves are small and dark green changing to yellow and orange in autumn. When the leaves fall in winter, crape myrtle becomes a living sculpture. The trunk and branches of tree-form plants have an attractively gnarled, sinuous character with smooth bark. Seeds are narcotic. In Manipur, flowers and leaves are used as purgatives. Bark is stimulant and febrifuge (fever removing). Roots are astringent and used as gargle.

Hibiscus a well known member of the family Malvaceae, grows as an evergreen shrub plant. The plant is extensively cultivated as an ornamental plant that bears large flowers on the bushy hedges. These enormous flowers are usually dark red in colour and are not usually fragrant. The huge size and the reddish colour and hues attract humming birds (Kumar and Singh, 2012). The generic name is derived from the Greek word “hibiskos” which was the name Pedanius Dioscorides gave to Althaea officinalis. Hibiscus rosa-sinensis was named by Carolus Linnaeus. The Latin term “rosa-sinensis” literally means “rose of China”, though it is not closely related to the true roses. Member species are often noted for their showy flowers and are commonly known simply as hibiscus, or less widely known as rose mallow. The hibiscus is used as an offering to goddess Kali and Lord Ganesha in Hindu worship. Hibiscus is an important flowering and garden plant. It has various medicinal values (Chopra et al., 1996 and Sayed et al., 2012).

ORIGIN AND DISTRIBUTION

The ancestors of the modern exotic hibiscus were originally native to Mauritius, Madagascar, Fiji, Hawaii, China and India. Ornamentally most important species is Hibiscus rosa-sinensis. There is no known record of the history of the domestication of Hibiscus rosa-sinensis. In one view it is believed that the species is a native to China and was first cultivated by the Chinese for its showy flowers (Kimbrough, 1997). No extant wild populations of the species have however, been reported from that country. Another view holds that the species is a native of the South Indian Ocean islands of which Madagascar, the Mascarene Islands and the Rodriguez Islands are a part (Borssum Waalkes, 1966). This view is strengthened by the fact that three Hibiscus species genetically compatible with H. rosa-sinensis are native to this area (Singh and Khoshoo, 1989). It is thought that the species was collected and domesticated on these islands by far easterner during their westward migration.

The genus Hydrangea is the best-known member of family Hydrangeaceae tribe Hydrangeae from the Asterid order Cornales. With more than two centuries of horticultural trade, Hydrangea cultivars are among the most popular ornamental shrubs worldwide (McClintock, 1957 and Kardos et al., 2009). Hydrangea (Hortensia) is a very popular ornamental plant for gardens. Hydrangeas occur most often on partly shaded but open slopes, rock edges, cliffs, roadside banks, edges of woods, or in moist open woods. Usually, restricted to the more moist, protected slopes. Recently it is commercialized for the production of cut flowers (Sacco et al., 2012). In India is widely grown in hilly areas.

ORIGIN AND DISTRIBUTION

The species of genus Hydrangea L. grow naturally in temperate areas of Eastern Asia, including some Pacific islands adjacent to Eastern Asia (Philippines, Taiwan, etc.), in temperate Northeastern America, in subtropical Middle and South America (McClintock, 1957). Throughout the eastern United States, ranging from the middle Atlantic States southward through the Southern Appalachians, and westward into the Ozarks and lower Midwest, numerous populations of shrubs with large, ovate, opposite leaves and compound cymes of small white flowers are en-countered. These are the wild hydrangeas.

SPECIES

Hydrangea is a genus of about 75 species of flowering plants native to southern and eastern Asia and North and South America. Most are shrubs 1-3 tall, but some are small trees and others lianas (Sacco et al., 2012). Species differ qualitatively in flavonoid constituents.

Ixora is an ornamental plant which is a medium-sized, tropical flowering, evergreen shrub that is used in landscapes. The genus Ixora belongs to the family Rubiaceae. The plants have glossy green leaves which are arranged oppositely along each stem. All Ixoras produce clusters of star-shaped flowers on stem tips or terminal growth. They are grown for their beautiful flowers which bloom in summer in clusters of different shades of red, pink or yellow (De Block, 1998 and Husain and Paul, 1988). The colour of the wild flowers is red or reddish-orange but ornamental varieties may have white, yellow, salmon or pink flowers. It is commonly known as West Indian Jasmine. The other common names of this plant are Jungle Geranium, Flame of the Woods, Jungle Flame, Burning Love, Red Ixora, Ixora, Amor Ardiente, Cruz de Malta, Dola de Coral, Equisosea and Rajana (Griffiths,1994 and Liogier,1997), Rangan, Kheme, Ponna, Chann Tanea, Techi, Pan, Santan, Jarum-Jarum and many more. Members of Ixora prefer acidic soil and are suitable for bonsai (Frommer, 2001). I. coccinea is used extensively for landscaping and is also grown as a potted ornamental (Lakshmanan et al., 1997). Ixora coccinea and Ixora parviflora are generally used as the ornamental plants in gardens and parks.

It is also a popular choice for hedges in parts of South East Asia like Thailand. Red Ixora flowers are commonly used in Hindu worship as well as in Indian folk medicine. The flowers, leaves, roots and the stems are used to treat various ailments in the Indian traditional system of medicine, the Ayurveda. The fruits are used as a dietary source. The plant possesses antioxidative, antibacterial, gastroprotective, hepatoprotective, antidiarrhoeal, antinociceptive, antimutagenic, antineoplastic and chemopreventive effects. The oil extracted from the flowers is helpful in conditions like scabies, eczema, pruritis and other skin infections. It is also used for hedges and borders and planted as an indoor potted plant. In laboratory tests, extracts of Jungle Geranium have shown anti-bacterial (Kumer et al., 1997) and anti-tumour (Serrame and Lim-Sylianco, 1995 and Latha and Panikkar, 2000) activity. From a methanol extract of the flowers, 13 chemicals were identified including ursolic acid which has known antitumor and antiviral activity (Monteath et al., 2001). In the traditional medicine of India, infusions of the leaves and juice from the roots are used to treat a wide variety of ailments including dysentery, ulcers, and gonorrhea (Parrotta, 2001).

Nerium (Nerium oleander L.) belongs to family Apocynaceae is a Mediterranean evergreen shrub characteristic of watercourses, gravely places and damp slopes (Portis et al., 2004 and Herrera, 1991). The first Oleanders came to subtropical Galveston in 1841. Joseph Osterman, a prominent merchant, brought them from Jamaica. After distributing these oleanders, these new plants were growing throughout the city. Later as early as 1908, an editorial in the Galveston Tribune observed that the oleander was emblematic of Galveston. In 1910, The Galveston Daily News also reported that Galveston was known throughout the world as “The Oleander City” and in 1916, an article named it one of the most beautiful cities in the South. It is widely grown as an ornamental in warm temperate and subtropical regions, due to its abundant and long-lasting flowering and moderate hardiness. It is used for screens, hedging along highways, planting along beaches and in urban areas as, by removing suckers and leaving just a few stems, it can also be formed into very attractive small trees (Portis et al., 2004). Nerium oleander is among the most toxic of all ornamental plants. More than fifty toxins have been isolated, including cardiac glycosides, general cell toxins and the strychnine-like compound rosagenin. The ancient city of Volubilis in Morocco took its name from the old Latin name for the flower.

Rhododendron belongs to family Ericaceae. The word “Rhododendron” is derived from the ancient Greek word “rhódon” which means rose and “déndron” which means tree. This genus is characterized by shrubs and small to (rarely) large trees. The smallest species grow up to 10–100 cm tall and the largest Rhododendron giganteum is reported to grow over 30 m tall. They are noted for their clusters of large flowers. The alpine species have small flowers and small leaves and tropical species grow as epiphytes. The colour of the rhododendron flower is available in nearly every colour of the rainbow including various shades of blue, yellow, pink white, red, orange and purple. Rhododendron flower from January through August, depending on the location and the climate.

Rhododendron tomentosum Harmaja has been used in ethnomedicine for the treatment of various ailments such as cough and cold, insect bites, rheumatism as well as a repellent. The essential oil of wild rosemary with rich polyphenolic fraction which possesses analgesic, anti-inflammatory, antimicrobial, antiviral, antifungal, insecticidal, antidiabetic, antioxidant and anticancer properties (Dampc et al., 2013).

ORIGIN AND DISTRIBUTION

Majority of Rhododendron species are native to the eastern Himalaya and southeast Tibet, Asia, North America, Europe and Australia along with the islands of Java, Sumatra, Borneo, New Guinea and the Philippines. The highest species diversity is found in the Himalayas from Uttarakhand, Nepal and Sikkim to Yunnan and Sichuan with other significant areas of diversity in the mountains of Korea, Japan and Taiwan. The rest are broadly spread throughout the northern hemisphere in relatively small isolated populations in Japan, northwestern North America, the Appalachian and the Caucasus Mountains. The tropical Rhododendron species range from south-east Asia to northern Australia with 55 known species in Borneo and 164 in New Guinea. Interestingly, the species in New Guinea are native to subalpine moist grasslands at around 3000 metres above sea level in the Central Highlands. Relatively fewer species occur in North America and Europe. The genus Rhododendron of Indian Himalayan Region (IHR) has been enumerated a total of 87 species, 12 subspecies and 8 varieties and have been recorded in IIHR. Among these 6 species and one subspecies are reported from Western Himalaya. The maximum concentration of 86% was observed in Arunachal Pradesh (75 species). The species of Rhododendron exhibit significant diversity in habit and broad range of distribution from the altitude of 800-6000 m and the best range is observed in 3001-3500 m altitudes. An analysis revealed that 20 taxa are endemic, 30 are rare, 24 are endangered, 3 are vulnerable and 47 taxa have to be assessed (Sekar and Srivastava, 2010). More than 50 hardy species of Rhododendron have been introduced from the wilds of China, Tibet, Bhutan and Vietnam since 1981 (Cox, 2012). George Forrest collected more than 400 Rhododendrons in China in between 1904 to 1932 for introduction to the western world (Geng, 2010).

Ageratum is a winter season annual that is grown for its beautiful flowers. It belongs to family Asteraceae. The word “Ageratum” is derived from the Greek words “ageras” meaning non-aging referring to the longevity of the whole plant. Ageratum houstonianum (flossflower, bluemink, blueweed, pussy foot, Mexican paintbrush) syn. Ageratum mexicanum Hort. is a cool-season annual plant often grown as bedding in gardens. Ageratum houstonianum is from Mexico and is named after William Houston (1695-1733), a Scottish physician who collected the first ageratum plants. The flowers are blue in colour (sometimes white, pink, or purple). The ray flowers are threadlike leading to the common name and are used for flower arrangements and potted ageratum plants are used for beautification of the surroundings. Growing ageratum is very easy under suitable climatic conditions. The genus Ageratum consists of some ornamental species, but only a few species have been phytochemically investigated (Burkill, 1985). A. houtsonianum contains essential oil the main constituents were precocene I (23.34%), precocene II (43.99%) and beta -caryophyllene (9.18%) (Menut et al., 1993 and Shahi et al., 1996).

ORIGIN AND DISTRIBUTION

Although ageratum is native to the Americas, Ageratum houstonianum, (floss flower), was known in Europe as early as the late 1600s or early 1700s, being routinely cultivated in European gardens by the 1800s (Johnson, 1971). Locations within which Ageratum houstonianum is naturalized include Australia, south-eastern USA, southern Europe, Africa, China, Japan, New Zealand and some Pacific islands. Ageratum houstonianum is invasive in parts Tanzania. A. houstonianum is naturalised in Kenya at 1500-2780 m altitude, specifically in the highlands: Mau, Aberdares, parts of Laikipia and Nyeri.

Impatiens balsamina (Balsam, Garden Balsam or Rose Balsam or Gulmehndi) is a species of Impatiens widely cultivated as an ornamental plant in landscaping belongs to the family Balsaminaceae. It is a qualitative short-day plant, propagated by seed and is one of the popular species of North India. It is called kamantigue in the Philippines. This species of Kamantigue are used in teas. In many English speaking countries they are known as “Touch me not”, possibly due to the ripe seed pods explosively bursting when touched. Different parts of the plant are used to treat disease and skin afflictions such as the leaves, seeds, and stems. It is also edible if cooked. Juice from balsam leaves treats warts and also snakebite, while the flower can be applied to burns to cool the skin. Impatiens balsamina L. has been used as indigenous medicine in Asia for the treatment of rheumatism, fractures, and fingernail inflammation. In Korean folk medicine Impatiens (‘Bong Seon Wha Dae’) has been used to cure constipation and acute gastritis by meat. There are mainly four forms of I. balsamina namely red, purples, white and pink.

ORIGIN AND DISTRIBUTION

Impatiens balsamina is a species of Impatiens native to southern Asia in India and Burma, but has been cultivated widely. It is now naturalized in many tropical and temperate areas of the world. Jones and Smith in 1966 proposed the Himalayan region as the centre of origin. The major centres of diversity are in highlands and mountains of tropical and sub-tropical Africa, Southeast Asia and the Indian sub-continent. In the U.S., Impatiens balsamina is found primarily in a wide strip encompassing the Northeast and Southeast regions from Florida to New York with specimens being found as far west as Missouri. Impatiens denisonii is a scapigerous herb which is found only in the Western Ghats in South India and are endemic in the Nilgiri Hills. Impatiens ecornuta, the spurless touch-me-not or western touch-me-not, is an annual flowering plant native to the northwestern United States and British Columbia in Canada. Impatiens flaccida is native to the Western Ghats in India and to Sri Lanka whereas, Impatiens hawkeri (New Guinea impatiens) is native to Papua New Guinea and the Solomon Islands. It has been bred and hybridized in cultivation to produce a line of garden plants. The species has been crossed with Impatiens aurantiaca and I. platypetala to improve characteristics such as drought-resistance. Impatiens irvingii is native to tropical Africa. Impatiens namchabarwensis (Blue Diamond Impatiens) is a 40–50 cm tall perennial plant, native to the Himalaya overwintering by a thick fleshy rootstock. Impatiens psittacina, known variously as the “parrot flower” or “parrot balsam” is a species of balsam from Southeast Asia that was described by the botanist Joseph Dalton Hooker and was noted for its flower that resemble a “flying cockatoo”. It is known from Thailand, Burma and parts of India (Morgan, 2007). Impatiens sodenii is native to Kenya and Tanzania. It is widely cultivated as an ornamental plant. I. walleriana is native to East Africa and yielded ‘Elfin’ series of cultivars, which was subsequently improved as the Super Elfin series.

Cosmos is a flowering plant belongs to family Asteraceae. Cosmos bipinnatus is ornamentally important species grown for garden display. The word cosmos is derived from the Greek word “kosmos”, which means a balanced universe or order, harmony and often referred to as Mexican Aster. The species name is from the Latin “bipinnatus” meaning “twice-pinnate” The botanical epithet is from the Latin “pinnatus” meaning “with leaflets arranged in opposite pairs”. Cosmos flowers are produced in a capitulum. Modern varieties come with single or double flowers, picotee edges, and even furled petals in the variety Seashells. Ornamental uses of cosmos include cut flowers and as border annual in the gardens. It is a very popular flower for summer bedding. Cosmos has a pleasant aroma and attracts butterflies to the garden. Essential oil extracted from leaves of cosmos. The major constituent of C. bipinnatus contained 15-17% beta-elemene, 15-17% beta-caryophyllene, 10-21% germacrene D and 12-15% bicyclogermacrene (Menut et al., 2000).

ORIGIN AND DISTRIBUTION

Cosmos is native to scrub and meadowland in Mexico where most of the species occur, Florida and the southern United States, Arizona, Central America, and to South America in the north to Paraguay in the south.

It can also be found in natural areas in much of North America, where it is a garden escape (introduced species) and in some habitats becoming a weed. Cosmos sulphureus originates from Central America (Mexico) and northern South America, where it is still found in the wild. It has been introduced as an ornamental in many countries all over the world, in tropical Africa e.g. in Senegal, Cameroon, Sudan, Tanzania, Malawi, Zambia, Zimbabwe, Mozambique, Réunion and Mauritius. Sometimes it has escaped from cultivation and behaves like a weed, e.g. in Tanzania, Malawi, Zimbabwe, the United States and Canada. Cosmos caudatus is indigenous to tropical America. It was introduced by Spaniards into the Philippines, possibly because it was used by them as a vegetable at sea. Now it is pantropical, including Southeast Asia, where it is cultivated but also occurs in a naturalized state.

Impatiens is the most popular bedding plant grown worldwide. The genus Impatiens is estimated to contain about 850 species (Grey-Wilson, 1980b). The majority is native to tropical and subtropical regions of India and Africa. The popularity of Impatiens walleriana is mainly due to its propensity for producing large numbers of flowers under low light intensity (Simmonds, 1980). Due to the high economic value and consumer demand for bedding impatiens, there has been a concerted effort by plant breeders to release a wide range of cultivars having different flower colours and distinctive foliage. Previously known as I. sultanior, I. holstii, it has several common names including “Busy Lizzie” and “Patience Plant”. It is one of two important groups of Impatiens in the horticulture industry with the New Guinea Impatiens (Impatiens hawkeri) group being the other. Despite being Impatiens walleriana is one of the most important bedding plants in the world, information on I. walleriana relatively scarce. Impatiens walleriana continues to lead as one of the three most important bedding plants worldwide. It is available as both seed and vegetative products. The history of its development, marketing success, wide adaptability, a large palette of flower colours and forms and unparalleled garden performance as a bedding plant for shade are described as an aid for continued crop development with breeding lessons for other flowering crops.

ORIGIN AND DISTRIBUTION

Jones and Smith (1966) proposed the Himalayan region as the centre of origin. Khoshoo (1957) and Gill and Chinnappa (1977) stated that the genus Impatiens contains over 600 species half of which occur in the Indian subcontinent. The major centers of diversity are in the highlands and mountains of tropical and sub-tropical India, Africa and Southeast Asia. There are only a few Holarctic species and none indigenous to South America or Australia (Zinov’ea-Stahevitch, and Grant, 1984). Impatiens walleriana also known by the names I. sultani Hook. f. and I. holstii Engl. is native to areas of Eastern Equatorial Africa including Kenya, Tanzania, Mozambique Malawi and Rhodesia; as well as Zanzibar and Pemba Islands.

Typically, African impatiens are highly endemic forest species, which thrive in moist semi-shade areas, and often in high altitude regions that receive ample rainfall (Grey-Wilson, 1980). Nearly all African Impatiens are native to habitats above 800 m and one third can only be found in habitats above 1500 m. However, I. walleriana may also thrive at lower elevations provided that these areas receive increased rainfall from monsoons (Grey-Wilson, 1980).

Pansy belongs to the family Violaceae, genus Viola and species tricolor. Pansy also known as butterfly flower, cat face. Pansies are annuals or short-lived perennials, grow 15-30 cm tall and have heart-shaped leaves at the base and oblong leaves growing from the stems. The pansy is quite durable and a “flower for all seasons”. The fragrant and edible blooms are desirable in gardens. Pansy popularity increases possible due to its ease of growing. Whether grown from seed or bedding plants, pansies are relatively disease and pest free blooming prolifically for the gardener’s enjoyment. The pansy is a group of hybrid plants cultivated as garden flowers. Pansies are derived from Viola species Viola tricolor hybridized with other Viola species, these hybrids are referred to as Viola × wittrockiana or less commonly Viola tricolor hortensis. The pansy is used in phytotherapy. The pansy is the symbol of Free thought. For Viola species, there is strong resistance to cold, flowering early and long flowering period. Also be used to cover a large area on the ground flower beds, its colour range, forming a unique landscape in early spring, but also in the flower bed with the string of red, petunia colour, or for potted plants and planted tank, decorative balconies, bay windows and stairs.

ORIGIN AND DISTRIBUTION

The modern pansy, Viola x wittrockiana, is thought to have derived from Viola tricolor, a native of central Europe. The center of origin for Viola was continental Europe. Viola is widely distributed in temperate areas in the northern hemisphere and in S. America, with centres of diversity in S.E. Europe, E. Asia and S. America; isolated endemics occur in Africa (equatorial high mountains and the Cape), E. Australia, Tasmania, New Zealand and Hawaii. V. sororia as defined by McKinney (1992), is widely found across the United States and Canada. Each subspecies has a smaller distribution. V. sororia var. sororia is found in the mid to eastern United States and southern Canada, V. sororia var. affinis, is found in western and extreme northeastern sections of the United States and Canada, V. sororia var. missouriensis is found in the eastern United States, and V. sororia var. novae-angliae is found in Minnesota, Wisconsin, Maine, Quebec and New Brunswick. Of the four varieties only V. sororia var. sororia and V. sororia var. missouriensis are native to New Jersey (McKinney, 1992). V. sororia var. sororia is found in drier areas than the other four subspecies and often in waste grounds (McKinney, 1992) or on the forest floors of open woods in semi-shaded conditions (McKinney, 1992).

Petunias (Petunia spp.) are annual or perennial plants belonging to Solanaceae family. The common kinds are rather weedy in habit, but their great profusion of bloom under all conditions makes them useful and popular. They are small herbs grown for their showy, often fragrant flower. The geographic distribution includes temperate and subtropical regions of Argentina, Uruguay, Paraguay, Bolivia and Brazil, with a centre of diversity in Southern Brazil. For longer flowering season they may be grown in bed borders, edgings, rock garden, window boxes, hanging baskets and pots. Petunia is considered to be the first cultivated bedding plant and has remained as a commercially important ornamental crop since the early days of horticulture and is one of the favourite genera for developing new varieties. Apart from its significance as an ornamental crop, petunia has proved to be one of the most excellent model crops for studies on gene regulation and genome structure, since the system combines innumerable and excellent technical features with a broad range of research possibilities.

ORIGIN AND DISTRIBUTION

Petunia is endemic to South America, with subtropical distribution ranging from 22^o to 39^oS. The major species richness is found in Brazil followed by Argentina, Uruguay, Paraguay, and Bolivia. All species occur in Brazil, except for P. occidentalis, which has a disjunct distribution restricted to the Sub-Andean mountains in northwestern Argentina and southern Bolivia. The Serra do Sudeste and neighbouring places in southern Rio Grande do Sul have a low-altitude mountain range and a set of diverse edaphic conditions. Petunia integrifolia and P. axillaris, parental species of garden petunia, are sympatric in these areas. Five species of Petunia grow in Serra do Sudeste, three of them namely P. bajeensis, P. exserta, and P. secreta are strict endemics. In the border of the Serra Geral in the state of Santa Catarina species of Petunia grow associated with grasslands, along forest borders, or on outcrops associated with Araucaria moist forests, at altitudes ranging from 800 to 1800 m. For this area the occurrence of four species, three of them strict endemics, P. bonjardinensis, P. reitzii and P. saxicola, restricted to the higher area of the plateau in Santa Catarina. There are two major disjunct areas of occurrence of Petunia: the Serra da Mantiqueira in Minas Gerais, Brazil, and the Sub-Andean region in Argentina and Bolivia. In the first, only P. mantiqueirensis is found, an endemic species phylogenetically related to the Brazilian highland group. The subtropical range of Petunia, with centers of diversity in southern Brazil, overlaps with that of Calibrachoa.

Phlox is a perennial and annual flowering plant belongs to family Polemoniaceae. “Phlox” is a Greek word meaning “flame” and was most likely named thusly due to its bright and vivid colours. Phlox originally came from North America and was available in England by the early 1800s. It quickly grew in popularity and today it is still found growing wild in gardens across the world. Among perennials, Phlox paniculata, Phlox divariecata, Phlox glaberrima are earliest species to be cultivated and reached to England and France from Virginia (USA) in the early 18^th century. Among annuals, Phlox drummondii is commonly grown in India. Annual phlox is propagated by seeds, whereas, cutting is used as propagating material for perennial species. Phlox is grown in the garden as bedding and border plant for its dramatic, fragrant, showy and long blooming flowers. The colour range includes white, rose, pink, purple, lavender, violet, pale blue, bright red and magenta. Some flowers are bicoloured.

ORIGIN AND DISTRIBUTION

Phlox is native to North America except one species i.e. Phlox sibirica which originated from Siberia (Meyer, 1944). They are found mostly in North America in diverse habitats from alpine Tundra to open woodland and prairie. Some flower in spring, others in summer and fall. Many are fragrant.

The diversity of species and genera is particularly high in California, USA, where 17 genera and over 170 species occur. Significant diversity also exists elsewhere in the world. A principle lineage consisting of Cantua, Cobaea, and Bonplandia is distributed natively only in Mexico, central America and northwestern South America. In Eastern North America, the genus Phlox is unusually diverse compared to the rest of the family. Other than members of Phlox, only a few species occur natively east of the Mississippi river in the United States, such as Ipomopsis rubra, Collomia linearis and a few Polemonium. A few Phlox and Polemonium species are also found natively in Eurasia. Central and South America, particularly the western regions of South America, are also home to some members of the phlox family. A small number of species from several genera that are most abundant in North America, such as Collomia, Gilia, Navarretia and Leptosiphon are found only in western South America, indicating multiple instances of long distance dispersal (Grant, 1959 and Morrell et al., 2000). Occasional species, such as skunkweed (Navarretia squarrosa) and Collomia grandiflora, have become weedy in parts of Europe and Australia and some cultivated species, such as members of Cobaea, have become naturalized outside their native range (Grant, 1959, Hussey et al., 1997, Pysek et al., 2002 and Anon., 2003).

Salvia belongs to family Lamiaceae. The genus Salvia comprises about 900 species which are grown for their ornamental flowers since they make excellent and showy borders in gardens. One of the species most commonly grown is Salvia splendens is a tender herbaceous perennial, but grown in India as winter season annual flowering plant. It bears racemes of bright scarlet flowers of large size. It has ability to grow under partial shade condition. It is commonly grown as bedding plant due to varying colours mostly scarlet, purple, orange, lavender and yellow and long lasting flowers. The word salvia was derived from Latin word ‘Salvare’ meaning ‘to heal or to be safe and unharmed’ (Blumenthal et al., 2000 and Kamatou et al., 2008) later it was translated in French as “sauge” or “sage” and in old English “Sawge” (Kamatou et al., 2008). Salvia has several ornamental, culinary and medicinal species (Codd, 1985, Paton, 1991, Gali-Muhtasib et al., 2000, Kamatou et al., 2008 and Bruna et al., 2006). It is also used in preservation of food, mainly meat and cheese, due to its antioxidant properties, as well a spice for flavouring food articles (Topuc, 2006). Chinese use its species to increase longivity and Roman use it in ceremonies as scared herb (Kamatou et al., 2008). The salvia species contain secondary metabolite the main are terpenoids and flavonoids and monoterpenes present in aerial parts of plant like flower and leaves and diterpenoids mostly in roots (Topuc, 2006).

ORIGIN AND DISTRIBUTION

The centre of origin of salvia is considered to be Afghanistan and Soviet Central Asia as a large number of primitive morphological species are present but the most of the diversity or species are present in Mexico (Paton, 1991 and Kamatou et al., 2008). The genus is sub-cosmopolitantly distributed worldwide, but is absent in the North and most of the low-lying tropical areas of the world such as the Amazon basin and central and west Africa (Paton, 1991), Jager and Van Staden (2000) and Kamatou et al. (2008) reported its absence not only in western Africa but also in central tropical Africa, Hedge (1974) and Kamatou et al. (2008) reported that West and the southern parts of Africa has greatest number of species (Kamatou et al., 2008).

The genus Salvia contains at least 900 species, because they readily cross pollinate, innumerable hybrids - both natural and manmade. Salvias are found on almost every continent in the world. Pliny the Elder, a Roman naturalist, wrote about their healing qualities back in the first century. In the early 17^th century, the English botanist John Gerard, in his famous Herbal, described a number of sages, including common garden sage and one that sounds similar to what we now call ‘Tricolor’ sage. He referred to the healing powers of these herbs as well. Until the 19^th century, most gardeners focused on growing plants for medicinal or culinary purposes; beauty was a secondary, much less important consideration.

The results of plant exploration in the 18^th and 19^th centuries brought scores of new salvias to English and European gardeners from Mexico, China and Africa. One, Salvia buchananii, was found in Mexico by an English woman, who gave it to a man serving in the army. Salvia coccinea, indigenous to Mexico and South America, was grown for decades as a wildflower. Both scarlet sage and mealy cup sage were discovered in the early 1800’s, the former in Brazil, the latter in Texas.

Zinnia is a very important summer annual belongs to family Compositae. Zinnia was named for the man who wrote the first scientific description of the flower, “Dr. Johann Gottfried Zinn” a German Professor of medicine, but it was the late 19^th century that plant breeders started to pay any attention to this plant. Zinnia is a half hardy plant. They are popular for bedding however, cut flowers of zinnia remain fresh for several days. They are easy to grow from seeds. Collection of open pollinated seeds is in common practice in India. Non-uniformity of bloom with respect to colour, flower shape and size, height of the plants and excessive etiolation of the plants result into poor sale of zinnias.

ORIGIN AND DISTRIBUTION

The genus Zinnia consists of 20 species, all native to the New World (Bailey, 1951). Further Stemart and Thomas (2007) suggested that zinnia are native to scrub and dry grassland in an area stretching from the Southwestern United States to South America, with a centre of diversity in Mexico.

Zinnias are grown mostly as annual in Mexico, Texas, New Mexico, Colorado, Brazil and Chile. It is sometimes called the Mexican marigold as its designation in some degree is justified in case of the yellow varieties. In early days zinnias were not popular. Although native to North and South America, not everyone found them attractive or desirable as a landscape plant. In fact, when Spanish first saw the zinnia species in Mexico, they considered the flower so unattractive that they named it “mal de ojos” which is Spanish for “Sickness of eye”. Zinnia seeds brought back to Europe in eighteenth century caused little excitement although the plant did not get good name. But it was not until the late nineteenth century that plant breeders started to pay any attention to this species.

The start of real popularity of the zinnia came around 1920 when Bodger Seeds Ltd. introduced the dahlia flowers Giant Dahlia. John Bodger discovered it as a natural mutation in a field of Mammoth and within the next few years selected the California Giant (large, flat-flowered variety) from the strain. The most attractive feature was availability of flowers in different colours. It also was considered to be a new trend in plant habit and flower form. It even won a gold medal from the Royal Horticultural Society of England, making everyone want to grow this prize winning flower. The many garden form of Zinnia elegans developed from the wild plant that grown in Mexico. Common zinnia has escaped and naturalized in part of southern United States including central Florida. Recently cultivation of new hybrid zinnias have started in some American and European countries under open as well as protected conditions for cut flower production.

Begonia is a perennial flowering plant belongs to family Begoniaceae. Begonia has rich colour and beautiful form of flowers. It is free flowering and striking foliage with free growth. The name Begonia is given by Franciscan monk Charles Plumier a plant which he found during his journey from Haiti to island Martinique. He dedicated this plant to “Michel Begon” the man who had the direct manmade over the expeditions. Begonia is easy to propagate and grown from seeds and vegetative means particularly cuttings. It is a popular flowering potted plant grown in containers and hanging baskets including tuberous, semperflorens, Rex, Elatior, Loraine and gracilis. Modern commercially cultivated begonias are mostly hybrids between wild types from all over the world.

ORIGIN AND DISTRIBUTION

Begonias are native to South America and second centre of diversity is Asia from Himalayas to Southern China and Malaysia (a floristic region that encompasses Malaysia, Indonesia, Brunes, Philippines and Paera New Guinea).

The distribution of Begonia diversity is uneven throughout tropical regions, with the greatest diversity in America and Asia (>600 species each), whilst being relatively species poor in Africa (160 species) and absent in Australia (Goodall-Copestake et al., 2010). The genus is thought to have originated in Africa, while South American and South East Asian species are the results of parallel radiations over the last 20-50 million years (Plana et al., 2004, Goodall Copestake et al., 2010 and Thomas et al., 2011). Long distance dispersal is rare, for example Begonia species have failed to cross the Torres Strait from Papua New Guinea to Australia.

Cactus (Opuntia ficus-indica), commonly known as prickly pear, belongs to the family Cactaceae. In local parlence, cactus is called nagphani or danda thohar. In Tamil Nadu, it is commonly known as chapathi balli. The word “cactus” derived through Latin from the ancient Greek kaktos, a name used by Theophrastus for a spiny plant (Johnson et al., 1972) which may have been the Cynara cardunculus (Sonnante et al., 2007). It is a storehouse of virtues that have been commercially unexploited so far in India. In addition, certain genera, such as Optuntia and Nopalea have economically useful plant parts. Different parts of the cactus can be used as fruit and vegetable for human consumption, fodder for cattle, and raw material for various industries to prepare plywood, soap, dyes, adhesives and glue, pharmaceutical products for treating blood sugar and various other disorders, and cosmetics such as shampoo, cream, and body lotions, etc. (Barbera et al., 1995 and Pimienta, 1994). Similarly, the tender young pads of Optunia and Nopalea species, known as nopalitos, are extensively used as a fresh green vegetable in Mexico and Texas. Even its seeds can be used as flavouring agents. Use of cactus pear as a waterproof paint for homes is also reported.

Cacti in pots may be placed outside in the summer to ornament gardens or patios, and then kept under cover during the winter (Anderson, 1999). Less drought-resistant epiphytes, such as epiphyllum hybrids, Schlumbergera also called Thanksgiving or Christmas cactus and Hatiora called the Easter cactus, are widely cultivated as houseplants. Cacti may also be planted outdoors in regions with suitable climates. Concern for water conservation in arid regions has led to the promotion of xeriscaping.

Dahlia (Dahlia spp.) syn. Georgina belongs to family Compositae (Asteraceae). Dahlia was named after “Professor Andreas Dahl”, a Swedish pupil of Linnaeus and author of Observations Botanicae. In India, dahlia is grown as potted plant and landscape uses but it is a poor crop as commercial flower due to shorter commercial life and its potentialities have not been exploited so far. Therefore, there is need to originate more and more new quality cultivars. Dahlias are half-hardy perennials with tuberous roots. Stems are mostly erect, branched, glabrous or scabrous. The leaves 1-3 pinnate, with slightly serrated margin are produced opposite at each node on the stem. They bear flowers on a long, stiff stems well above the foliage. Ray florets are neutral or pinnate and disc florets perfect.

ORIGIN AND DISTRIBUTION

The wild species of Dahlia are natives of Mexico and Central America, where some hybridization and selection had probably already occurred prior to their introduction into Europe at the end of the 18^th century (Crane et al., 1947 and Sorensen, 1969). The dahlia has been in Europe for over 200 years. It came from Mexico to the Botanical Gardens in Madrid towards the end of the 18^th century and was named by Abbe Cavanille in honour of Andreas Dahl, Swedish scientist-cum-environmentalist. The dahlia was introduced into England in 1803, but from a few varieties it soon had more than 300 varieties within the first 15 years. The initial named species imported into Europe were D. pinnata, D. rosea and D. coccinea. The first dahlias grown outside of Madrid were single (open-centred) and multi-ray open centre flowered, but it was not long before the horticultural growers of the day discovered the dahlia was a natural hybrid and when grown from seed, it readily changed its form and colour, Thus it has a range of different types. Further introduction, accompanied by hybridization and selection, have resulted in the production of a wide range of flower, forms and colours. Most of the garden types have been developed from D. variabilis. The first double flowered varieties were called Show and Fancy types. The show were self-coloured, ball like flowers, while the Fancy ones were multi-coloured.

During the mid 1800’s, these Show and Fancy flowers attained cult status with gardeners and several thousand different varieties were recorded. Other forms followed, in 1829 the first Anemone flowered dahlia appeared and then in 1850 the first Pompon was raised in Germany and was named after the bobble on a French sailor’s hat. The origin of the cactus and Decorative type belongs to the arrival of ‘Juarrezii’. According to the written records it was important as a piece of tuber from Mexico in 1872 to Holland. M. Van de Berg of Uttrecht received this so called species from Mexico and released stock of the variety in 1874. Subsequently, ‘Juarrezii’, named after a President of Mexico, was introduced into the UK by W. Cullingford a Vice President of the NDS and distributed by H. Cannell after 1880. Collerettes are the last form of dahlia to have been raised, that has their origin in France and is due to sporting of dahlias at Jardin Botanique de Lyon at the end of the 19^th century.

Geranium (Pelargonium spp.) belongs to the family Geraniaceae. The name Pelargonium was introduced by Johannes Burman a Dutch Botanist in 1738, from the Greek word “Pelargos” means stork because the seed head looks like a stork’s beak. Due to their long and beak-shaped fruits, they are also known by the name of cranesbills. Geraniums are popular flowering plants and grown as decorative pot plants for indoor and outdoor. There is a world demand for the rose geranium essential oil of Pelargonium species which contains geraniol, linalool and citronellol, substitutes for the expensive attar of roses in the perfume trade. Pelargonium species was known for their medicinal value by the earliest indigenous people (Swanepoel, 2009).

ORIGIN AND DISTRIBUTION

The plants originated from South Africa (Swanepoel, 2009), as well as Reunion, Madagascar, Egypt and Morocco and were introduced to European countries such as Italy, Spain and France in the 17^th century. Geranium includes around 422 species of flowering annual, biennial and perennial plants. Both Geranium and Pelargonium are genera in the Family Geraniaceae. Linnaeus originally included all the species in one genus. Geranium, but they were later separated into two genera by Charles L’ Heritier in 1789. Although members of the Pelargonium genus are often referred to as ‘Pelargoniums’ to try to avoid confusion, many people still use the older common name of ‘Geranium’.

Most of the Pelargonium plants cultivated in Europe and North America have their origins in South Africa. Geranium robertianum is found throughout Europe, Asia and North Africa where it grows on a variety of soils, rocks, tree trunks and decaying organic matter such as logs. It is a component of virtually all forest types there. In the Pacific Northwest it is primarily found west of the Cascade crest although it extends along the Columbia River in Klickitat County. Ecological structure of Geranium robertianum L. populations under natural conditions and in the garden in Poland. Geranium farreri found in China, in south Gansu and north-west Sichuan.

Orchids belong to family Orchidaceae, the largest family of the flowering plants. The term ‘orchid’ has its origin from the Greek word, “orchid” meaning “testicle”, referring to the paired underground tubers of terrestrial orchids. There are several generas in orchids, which are popular for their separate importance as cut flower, pot plant, medicinal properties, flavour extraction, etc. The fascinating flowers exhibit an incredible range of shape, size and colour, long life of flowers on plant and an amazingly long keeping quality, which no other plant can claim.

ORIGIN AND DISTRIBUTION

Majority of the cultivated orchids are native of tropical countries and occur widely in humid tropical forests of South and Central America, Mexico, India, Ceylon, Burma, South China, Thailand, Malaysia, Philippines, New Guinea and Australia. Brazilean cattleyas, Mexican laelias and Indian dendrobiums, cymbidiums and vandas have been extensively utilized for the development of modern orchid industry in the world.

Poinsettia (Euphorbia pulcherrima) is one of the most popular ornamental pot plants belonging to the family Euphorbiaceae. The botanical name Euphorbia pulcherrima means very beautiful. Euphorbia pulcherrima the name originally given by German botanist Karl Ludwig Wilenow was changed to “Poinsettia” in honour of “Mr. Poinsett” in 1836 by William Prescott. Poinsettia is a short-day, non-food and non-feed vegetatively propagated ornamental plant. Poinsettias are fascinating winter blooming small shrubs or trees which can grow anywhere from about 0.6 to 5 m tall. The coloured bracts of poinsettia plants are actually leaves. Colours of the bracts can be red, pink, orange, white or marbled. These coloured bracts are caused by photo-periodism. Poinsettias have also been called the lobster flower and the flame-leaf flower due to the red colour. California is the top U.S. Poinsettia-producing state.

ORIGIN AND DISTRIBUTION

The poinsettia (Euphorbia pulcherrima) is the world’s most economically important potted plant but despite its preeminence it is not clear which wild populations are ancestral to the varieties cultivated around the world. Tradition holds that the U.S. envoy to Mexico, J. R. Poinsett collected the progenitors of the over 300 varieties in global cultivation on an 1828 excursion to northern Guerrero State, Mexico. It is unknown whether the contemporary cultivars are descended from plants from Guerrero or whether germplasm from other parts of poinsettia’s 2000 km long distribution entered into cultivation during the nearly 200 years of subsequent poinsettia horticulture.

The combination of nuclear and plastid haplotypes characterizing cultivars was found only in northern Guerrero. Whereas, distribution modeling indicated that suitable habitat conditions for wild poinsettias are present in this area consistent with their likely wild status. Finding shows that the area of northern Guerrero as the cultivated poinsettia’s probable ancestral region congruent with the traditional account attributing the original collections to Poinsett (Trejo et al., 2012). Poinsettias are originally native to the central and southern parts of Mexico where they grow as a shrub up to 5 m. The poinsettia was introduced to the United States by Mr. Poinsett in 1828. It was introduced into North America in1838 from Mexico and since that time it has achieved considerable economic importance as a pot plant in the florist trade.

Lotus belongs to the Nelumbonaceae family and the genus Nelumbo. There are two species in this genus; Nelumbo nucifera Gaertn. distributed in Asia and Oceania, and Nelumbo lutea distributed in North and South America (Qichao and Xingyan, 2005). Although, the species nucifera is the most important (commercially and culturally), it is critical to describe the American species, evaluate its horticultural value and its potential as a source of genetic diversity. The American species, represented by Nelumbo lutea (Syn. N. pentapetala or Nelumbium luteum) is known as American Lotus, Water-chinquapin and Yellow Lotus (Sayre, 2004) and is native to the eastern and central portions of the US ranging from Maine to Wisconsin and in the south from Florida to Texas. It is one of the most spectacular and graceful aquatics among all the native plants of India. N. indica are found all over India and extend as far as Kashmir to Kanyakumari exhibiting enormous thermoplasticity and phenotypic diversity with a large number of racial variants with different shapes, sizes and colours. First Indian fossilised record of N. nucifera has been reported from the Pleistocene epoch of Kashmir. The presence of Nelumbo in the Tertiary period of Assam is reported on the basis of impressions of leaves and rhizomes found in the collection from Eocene bed near Damalgiri. These records confirm the evidence in support of the view that N. nucifera is indigenous to India.

Lotus has good fragrance. About seventy compounds were identified with hydrocarbons representing > 75% of the extract. 1, 4 – Dimethoxy benzene, 10, 8 – Cineole, ferpinen – 4al and linalool were important constituents characterization of the scent of lotus flower (Omata et al., 1991).

Clematis is member of the Ranunculaceae family which also known as buttercup family. This cosmopolitan genus comprises climbing lianas, small shrubs and erect sub-shrubs distributed predominantly in the temperate zone of both hemispheres but with some species distributed in tropical areas (Tamura, 1995, Johnson, 1997, Grey-Wilson, 2000 and Wang and Li, 2005). The word clematis is taken from Greek as in “klema” meaning “a vine branch”. Most species are known as Clematis in English while some are also known as Traveller’s joy, Leather flower, Vase vine and Virgin’s bower the last three being names used for North American species (Chawla et al., 2012). Most Clematis is climbers (Roh and Song, 1997), however; two notable exceptions are the species C. heracleifolia and C. integrifolia which are herbaceous and fit well in a perennial garden border. The vast majority of these are very hardy. Some species however, particularly the evergreens can only take a few degrees of frost. Most Clematis varieties produce single flowers. Some varieties produce double flowers; others produce both single and double flowers. Clematis blossoms often change colour, some very marked through the life of each flower particularly when grown in full sun. Pastel colours will hold their colour best if grown in some shade. Many Clematis species are scented, although none are strongly perfumed. The most-highly scented is the tender species C. armandii. Montana types can also be relatively aromatic often with a scent reminiscent of vanilla. Of the large flowering hybrids, Fair Rosamund is the only one with any noticeable scent.

Sweet pea (Lathyrus odoratus) is the only species in the genus Lathyrus and family Fabaceae which is widely cultivated as an ornamental plant. Lathyrus comes from the Greek word “Lathyros” in which the prefix “la” means “very” and suffix “thyros” means “passionate”. The “Odoratus” is derived from Latin word which means “fragrant” (Fernald, 1950). It is mainly grown for its beautiful flower colour forms. It is an annual climbing plant growing to a height of 1-2 m with the support of a terminal tendril which twines around the plants and helps to climb. The illness caused by the ingestion of sweet pea is known as odoratism or sweet pea lathyrism. Sweet pea was used to verify Mendel’s work with the garden pea (Pisum sativum L.) in the early 1900s (Bateson, 1902). The genetical phenomenon of linkage was first demonstrated in the sweet pea. It is used prominently as a model organism to study flower development due to its large, colourful and fragrant flowers. The essential oils extracted from the sweet pea can be used in perfume blends.

ORIGIN AND DISTRIBUTION

Sweet pea (Lathyrus odoratus L.) was discovered in Sicily in 1695 (Rice, 2002). Its species are found both in the Old World and the New World. The main centres of diversity are the Mediterranean region, Asia Minor and North America as well as temperate South America and East Africa (Kupicha, 1977, Jackson and Yunus, 1984, Yamamoto et al., 1984 and Simola, 1986). It generally grows in temperate regions and has been found on all continents except Antarctica (Kenicer et al., 2009 and Kenicer et al., 2005). Its cultivation is popular not only in the United Kingdom and the United States but also in Europe, Russia, Egypt, New Zealand, Australia and Japan (Hambidge,

1996, Inoue, 1981, 2007 and Rice, 2002). There are some reports of commercial sweet pea cut flower production (Hammett, 2006, Inoue, 1981 and Parsons, 2004). A seed bank at the Chichester Collection was started in 1998 and stores around 900 cultivars and around 100 accessions of other species.

The students in batches will visit the laboratory of Plant Pathology for their acquaintance with different appliances, tools, glassware‘s and other miscellaneous items, which they will use for various exercises and experiments to be conducted. A list of some of them is given below:

Procedure

1.Peeled Potato slices are cooked in 500 ml of water by the time till they are easily penetrated by a glass rod.

2.Filtered with the help of muslin cloth.

3.Agar-agar is melted in another 500 ml of water.

4.Potato extract is added to the melted agar.

5.Dextrose is added in this mixture and stir well with the help of glass rod.

6.Make the volume to 1000 ml, by adding required water.

7.Medium is sterilized in an autoclave at 15 lbs pressure for 20 minutes at temperature of 121.6^oC.

Isolation of fungal pathogens

a. From leaves

•Choose leaves with young lesions.

•The lesions along with some healthy portion are cut in small pieces.

•The leaf portion is surface sterilized with 0.1% HgCl₂ for 10-15 seconds and washed with sterilized water 4-6 times.

•After washing, infected leaf pieces are placed on PDA plates with a sterilized forcep.

•After two days of incubation at optimum temperature, bits of mycelium from the margins of leaf pieces are transferred to fresh PDA slants.

•In certain cases the leaves are incubated in moist chamber and growth

•from infected portion is transferred directly to culture media.

Collection and dry preservation of disease samples

Materials : Iron knife, hand lens, vasculum, pruning scissors, paper envelops and plant press with blotters and news papers.

Method

•Collect infected plant parts and place them in paper envelops (use separate envelops for different kinds of diseased specimensxsxs).

•Place envelops in vasculum and bring to the lab.

•Arrange leaves and herbaceous stems inside the folder newspaper sheet.

•Place the newspaper between the blotters in plant press and tighten the bolts.

•After proper drying remove dried specimen from the press and keep them in separate folders.

•Label each folder giving the following informations.

a.Name of the organism

b.Habitat

c.Locality

d.Date of collection

e.Name of collector

f.Collection number

g.Other notes

Koch‘s Postulates (Pathogenicity test)

Robert Koch developed the following postulates in 1883 on the basis of which an organism could be attributed to be the cause of a specific disease.

i)Recognition: The suspected organism must be found in every case of disease (Presence of organism in the diseased tissues).

ii)Isolation: The organism must be isolated in pure culture from every case of disease (Isolation in pure form).

iii)Inoculation: The isolated pure culture when introduced into the same species or variety of susceptible host must be capable of reproducing the original disease with its typical symptoms (Pathogenicity).

iv)Re-isolation: The organism must be re-isolated from the artificially infected host and its characteristics must be exactly like those observed in step 2 (This step was added by E.F. Smith).

If all the postulates are proved true, then the isolated pathogen is identified as the actual causal organism responsible for the disease.

Introduction

Chemicals that kill or retard fungi are fungicides. Most chemicals used to control plant diseases are ”protectants“ and must be applied before infection to protect the plant from invasion by a pathogen. Protectant fungicides are usually effective against a broad range of fungi and protect the plant against infection on the surfaces of the plant to which they are applied. Often, they require multiple applications during the growing season to maintain coverage as new growth emerges and weathering removes past coverage. A few chemicals are termed ”eradicants“ since they can eliminate an established infection. Some newer fungicides are systemic, meaning that they are absorbed by the foliage or roots and move within the plant to the site of infection. Systemic chemicals may be protectants, eradicants, or both systemic fungicides can be absorbed by the plant without harming it, and transported to other tissues where they are toxic to fungi. These compounds can control and eradicate established infections, but they are also vulnerable to fungi developing resistance, as they generally only target one step in a biosynthetic pathway to kill the fungus. To minimize the development of resistance by chemical overuse, fungicides are classified into groups based on their chemical activity.

Preparation of Bordeaux mixture

Materials: Iron, beaker, copper sulphate, lime, weighing balance, plastic container, wooden stick and muslin cloth.

Bordeaux mixture derives its name from the place of its discovery, Bordeaux, France.

Ingredients required for the preparation of 100 litre of 1 percent elicoid mixture are:

1.Copper sulphate (blue vitriol or bluestone) : 1 kg

2.Quick lime (unslaked) : 1 kg

3.Water 100 litres

Method

•Dissolve 1kg powdered copper sulphate crystals in 50 litres of water in a mudpot or plastic bucket.

•In another 50 litres of water dissolve 1kg of quicklime.

•Stir thoroughly with the help of wooden stick.

•Put a filter cloth on the mouth of 3^rd container.

•Pour the contents of both the containers in a 3^rd container simultaneously and stir it thoroughly.

•Make up the desire volume (ie. 100 litres).

•Test the mixture before use for the presence of free copper, which is harmful to the plant.

Introduction

Diseases are a common occurrence on plants, often having a significant economic impact on yield and quality, thus managing diseases is an essential component of production for most crops. These fungicides are used because of three main reasons:

a.To control a disease during the establishment and development of a crop.

b.To increase productivity of a crop and to reduce blemishes.

c.To improve the storage life and quality of harvested plants and produce.

Application Methods

To protect the crop from fungal pathogens, fungicides are applied in various formulations (as dust, granules, gas and most commonly, liquid). They are applied to:

1.Seed treatment

2.Soil treatment

3.Protection of standing crop

Poisoned food technique

The principle involved is to poison the medium with fungi toxicants and then allow a test fungus to grow on such medium. The test may be performed both on solid and liquid medium.

Procedure

On solid medium

•Prepare potato dextrose agar medium.

•Add required amount of fungicide and thoroughly mixed.

•The medium is poured into sterilized Petri-plates.

•A culture of test fungus is grown on PDA for a certain period (generally seven days) at the optimum temperature for growth.

•Small disc (7 mm) of fungus culture is cut with sterile cork borer and each Petri plates are centrally inoculated aseptically containing the medium with desired fungicidal concentration.

•Suitable checks are kept where the culture discs are grown under the same conditions on PDA without fungicide.

•The fungal colony diameter is measured at every 24 hr.

Biological control of disease employs natural enemies of pests or pathogens to eradicate or control their population. Interactions that lead to biocontrol can include antibiosis, competition, induction of host resistance, and predation. Some of the microbial taxa that have been successfully commercialized and are currently marketed include bacteria belonging to the genera Agrobacterium, Bacillus, Pseudomonas and Streptomyces and fungi belonging to the genera Ampelomyces, Candida, Coniothyrium and Trichoderma.

•Dual Culture Technique: For in vitro screening, performance of antagonist isolates in dual culture (Morton and Stroube, 1955) with test pathogen can be tested.

•Pour 15-20 ml of sterilized melted PDA in 9 cm Petriplates and allowed to solidify.

•Place the bits (5 mm) of the test pathogen and antagonist on the PDA plates opposite to each other from 1.0 cm from the periphery of plates (if both are fast growing) or place it 2-3 cm apart (if both are slow growing).

•The Petriplates are incubated (at 28 ± 2^oC) for desired duration.

•Periodical observation on the growth of the antagonists and the ability of the antagonist to colonise the pathogen are recorded.

Some basic informations about genera of Family Pythiaceae, Peronosporaceae and Albuginaceae;

Pythiaceae

Indeterminate (grows continuously) sporangiophores, have sporangia that are borne variously, but not in chains, on somatic hyphae or on sporangiophores. This family includes the genera Pythium and Phytophthora.

Peronosporaceae

Determinate sporangiophores, form sporangia on well-defined, branched sporangiophores of determinate growth. There are seven genera in the family including Basidiophora, Bremia, Bremiella, Peronospora, Plasmopara, Pseudoperonospora and Sclerospora.

Albuginaceae

Club shaped sporangiophores, catenate sporangia, produces chains of sporangia on club-shaped sporangiophores of indeterminate growth. The Albuginaceae contains a single genus Albugo.

Environmental stress can disrupt cellular structures and impair key physiological functions. Drought, salinity, and low temperature stress impose an osmotic stress that can lead to turgor loss. Membranes may become disorganized, proteins may undergo loss of activity or be denatured, and often excess levels of reactive oxygen species are produced leading to oxidative damage. As a consequence, inhibition of photosynthesis, metabolic dysfunction, and damage of cellular structures contribute to growth perturbances, reduced fertility, and premature senescence. Responses to environmental stresses occur at all levels of organization. Cellular responses to stress include adjustments of the membrane system, modifications of the cell wall architecture, and changes in cell cycle and cell division. In addition, plants alter metabolism in various ways, including production of compatible solutes that are able to stabilize proteins and cellular structures and/or to maintain cell turgor by osmotic adjustment, and redox metabolism to remove excess levels of ROS and re-establish the cellular redox balance. At the molecular level, gene expression is modified upon stress and epigenetic regulation plays an important role in the regulation of gene expression in response to environmental stress.

Climate change drastically influence water availability, salinity and several adverse soil conditions which will have direct bearing on original yields. Abiotic stress factors influence growth and secondary metabolite production in higher plants. The influences are well marked. In fact, productivities depend on the changed ecosystem also. Secondary metabolites play a major role in the adaptation of plants to the changing environment and in overcoming stress constraints. This flows from the large complexity of chemical types and interactions underlying various functions: structure stabilizing, determined by polymerisation and condensation of phenols and quinones, or by electrostatic interactions of polyamines with negatively charged loci in cell components, photoprotective, related to absorbance of visible light and UV radiation due to the presence of conjugated double bonds, antioxidant and antiradical, governed by the availability of –OH, –NH2, and –SH groupings, as well as aromatic nuclei and unsaturated aliphatic chains, signal transducing. Several plant-abiotic stress stimuli systems evidenced the multiplicity of biochemical mechanisms involved in the protective role of secondary metabolites:

Abiotic Stress in Plants
             
World population is growing at an alarming rate and may reach about 6 billion by the end of the year 2050. Though, the agricultural productivity is also being increased world over, yet it is not keeping pace to meet the demand of food availability. The main reasons for limiting the agricultural productivity are water shortage, depleting soil fertility and mainly various abiotic stresses and climatic change. Minimizing these loses is of primary concern for all nations to cope with the increasing food requirement. The abiotic stress is defined as the negative impact of non living factors on the living organism in a specific environment and abiotic stress is the most harm full factor concerning the growth and productivity of crops worldwide. Researches have shown that abiotic stressors are at their most harm full when they occur together in combination of abiotic stress factors (Mittler, 2006; Bianco and Defez, 2011). Numerous stresses caused by complex environmental conditions i.e. drought, too high and too low temperatures, freezing, salinity, UV light, heavy metals and recently through smog (air pollution) leading to substantial crop losses worldwide (Mahajan and Tuteja, 2005). The abiotic stresses might increase in the near future even because of global climatic change.

Plants that are affected by various abiotic stresses react differently as a result such as the reduction in organ size or a change in the antioxidant enzyme system, and while drought and heat are often studied separately, in nature they often occur together, meaning it is essential to carry out joint studies. Furthermore, and related to the above when we consider high temperature stress, one must always consider the use of water and nutrients by the plant and other physiological functions. The effects of heat stress can also be analyzed by the technique that measures lipid peroxidation in polyunsaturated acids of the plasma membrane. The accumulation of metals in plants, affects the normal processes of plant metabolism. The study shows that there is a relationship between high metal contents in plants and their modified morphology: strong reduction of leaf thickness, modified parenchyma structure, and decreased mitochondria organization were ascertained, although toxic symptoms were apparently absent. Water-deficit stress has a significant effect on plants growth and development, with primary affects on plant structure, leaf morphology and cell ultrastructure. Physiological processes such as stomatal conductance, photosynthesis and respiration are consequently impaired with further implications on the metabolic functions such as carbohydrate and energy production as well as carbohydrate translocation and utilization.

The stresses, drought, salinity, chemicals, cold and hot temperatures, have interconnected effects on plants, resulting in the disruption of protein homeostasis. Maintenance of proteins in their functional native conformations and preventing aggregation of non-native proteins are important for cell survival under stress. The heat shock proteins buffer this environmental variation and are therefore important factors for the maintenance of homeostasis across environmental regimes. Heat shock proteins are known to be expressed in plants experiencing high-temperature stress. Heat shock proteins are important in relation to stress resistance and adaptation to the environment. Their molecular function might be membrane or protein stabilization, but, for now, for most heat shock proteins the molecular function remains to be elucidated. The general observation of the response and induction of heat shock proteins following heat stress suggests that they play a fundamental role in cellular homeostasis. It is possible that heat shock proteins may be involved with the phenomenon of acquired thermotolerance. Heat stress disturbs cellular homeostasis and can lead to severe retardation in growth and development, and even death. Temperature stress can have also a devastating effect on both the plant anabolism and catabolism, initially acting on protein complexes, being the quaternary structure the first folding that is lost during heat stress or heating. Understanding the role of HSPs in relation to stress resistance in a more applied perspective as a potential indicator of stress is important. New technological developments make it possible to investigate the role of genes coding for heat shock proteins in greater detail. A combination of genomics and proteonomics will further elucidate the effects of stress on expression patterns at the DNA, RNA and protein level.

The extreme temperatures those are consequences of present-day global climate changes are considered as major abiotic stresses for crop plants. Different studies clearly show that temperatures exceeding the limits of adaptation substantially influence the metabolism, viability, physiology, and yield of many plants. Plants exposed to extreme temperatures often show a common response in the form of oxidative stress. However, the extent of damage caused by extreme temperatures depends greatly on the duration of the adverse temperature, the genotypes of the exposed plants, and their stage of growth. There is ample need to develop temperature tolerance in crop plants by exploring suitable strategies. Numerous research findings support the notion that induction and regulation of antioxidant defenses are necessary for obtaining substantial tolerance against environmental stress. The development of genetically engineered plants, by the introduction and/or overexpression of selected genes, would to be one feasible strategy. However, plant adaptation to either high temperature or low temperature is a multigenic response which is very complex in nature. Thus the task of identifying the traits those correlate with stress tolerance is incredibly difficult for researchers. Plant response to continuous light depends on plant tolerance and can be modified by alteration in temperature, light intensity, CO2 level, and other environmental factors.

Most food legumes have a long history of domestication almost as long as cereals, and during this time they have been subjected to conscious and unconscious selections for better adaptation to environmental condition as well as better seed yield. In general, crops during their ontogeny faces a number of abiotic stress viz., excessive and/or low soil water stress, soil salinity stress, high as well as low temperature stress. It has been well documented that crop yields would be greater in many cropping regions if more water were available. 
Availability of water for agriculture is being challenged increasingly because of growing demand for water from other sectors such as industry, urban use, and for social and environmental purposes. Water stress may conceivably arise either from an insufficient or from an excessive water activity in the plant’s environment. Many physiological characteristics are correlated with the water potential of mesophyll tissue but the correlations are species specific. There is a general hierarchy of sensitivities among general physiological activities. Most sensitive are cell expansion, cell wall synthesis, protochlorophyll formation, and nitrate reduction. Generally turgor pressure is still accepted as the best indicator of water stress in plants. The specific mechanism by which turgor regulate physiological function probably relate to cell walls and membranes. Cell membrane structure, and spatial arrangement of enzyme, transport channels, cellulose synthesis rosettes, and receptor proteins may be dependent on turgor pressure.

We do not know when intercropping began nor why early civilizations fostered its use. Whether by design or accident, intercroppinq dominated early agriculture and is still practiced in many areas of the world. With the advent of “modern” agriculture, intercropping began disappearing from many areas. This shift was driven primarily by mechanization and specialization. Despite pressures to abandon intercropping, it has survived and flourished Inereasing interest in sustainability and environrnental concerns have drifted attention back to intercropping as a means of better utilization of resources while preserving the environment.
Through intercropping, farmers can achieve the full production of the main crop and also an additional yield (bonus) associated with an increased plant population of the second component. Hence, intercropping can increase incomes obtained by smallholder farmers in areas where labor is not shortage, through reduction of economic risk and market fluctuation resulting from growing a single crop which is more prone to natural hazards and helping the farmers in better utilization of land by having more than one crop produced per unit area. Though all intercrops produced higher productivity, the farmers could better use the appropriate population of component crops in intercropping systems in order to maximize yield of both crops as well as total productivity. It is, therefore, important to support intercropping systems with appropriate agronomic practices such as timely irrigation, pest protection and the likes to sustain the cropping system in the countries where labor is not problem for proper management in general even though sometimes sole cropping may became more productive.

Marginal land areas will need to be used to meet the increasing requirement of future generations, especially in developing countries. These marginal areas commonly impose abiotic stresses on crops due to factors such as salinity, drought, flooding, low nutrients and aluminium or heavy metal toxicity. As a consequence, the growth and yield of crops from such areas is typically low and their quality in also poor. Endogenous plant growth regulators play an important role in regulating plant responses to abiotic stress by sensitizing growth and developmental processes. While the physiological and molecular mechanisms linked to the role of ABA and cytokinins in stress tolerance are well explained, there is growing interest to elucidate the associations of auxins, ethylene, gibberellins, brassinosteroids, and polyamines in stress tolerance mechanism and also on possible cross talk mechanism among different growth regulators during stress tolerance acquisition. Identification and characterization of the gene regulating synthesis of different endogenous growth regulators and recent progresses on hormonal signaling, mutant research, and physiological actions have provided scope for manipulating their biosynthetic pathways for developing transgenic crop plants with enhanced abiotic stress tolerance. Researches have also provided some leads in exploiting the potential of growth regulators in enhancing the resistance to abiotic stresses of crops. Plant growth-regulators (PGRs), are biochemical and chemical compounds stimulates plant growth and productivity when applied, even in small quantities at appropriate plant growth stages. These are being extensively used in agriculture to enhance the productivity in agricultural crops. Their central role in plant growth and development is through nutrient allocation and source-sink transitions while most of the plant bioregulators (PBRs) stimulate redox signaling under abiotic stress conditions.

Plant–water relations concern how plants control the hydration of their cells, including the collection of water from the soil, its transport within the plant and its loss by evaporation from the leaves. Flow of water through plant and soil over macroscopic distances is driven by gradients in hydrostatic pressure. Over microscopic distances it is driven by gradients in water potential. Evaporation of water from leaves is primarily controlled by stomata, and if not made good by the flow of water from soil through the plant to the leaves, results in the plants wilting. Plant water deficit is initiated as the crop demand for water exceeds the supply. The capacity of plants to meet the demand and thus avoid water deficit depends on their “hydraulic machinery.” This machinery involves firstly the reduction of net radiation by canopy albedo, thus reflecting part of the energy load on the plant. Secondly, it determines the ability to transport sufficient amount of water from the soil to the atmosphere via the stomata in order to provide for transpiration, transpirational cooling and carbon assimilation. Water is transported by way the soil-plant-atmosphere continuum and it is largely controlled by the resistances in the continuum as determined by root, stem, leaf, stomata and cuticular hydraulic resistances. The gross effects of deficient and of excessive soil moisture on plant growth are well known, but controversy has existed for many years around the question whether the so-called “‘available moisture” is equally available for plant growth or available only with such increasing difficulty that plant growth functions are retarded before the wilting point is reached. Various measurable aspects of plant growth do not respond in the same manner to increasing moisture stress. Crops will respond to irrigations, although measured soil moisture stress is quite low. Problems of relating plant growth to soil moisture stress conditions varying with both time and soil depth are considered. Soil factors affecting density or depth are reviewed and several ways weather factors influence soil, -moisture-plant-growth relations summarized.

Partitioning of assimilated carbon among sink organs is a critical factor that controls the rate and pattern of plant growth. Environmental stress often restricts resource availability while successful acclimation sets in motion processes that restore the supply. A key mechanism contributing to regulation of carbon partitioning is an expression of genes that control activity of the enzymes which initiate sucrose metabolism at specific sites and stages of ontogeny. Drought stress not only limits the size of the source and sink tissues but the phloem loading, assimilate translocation and dry matter portioning are also impaired. However, the extent of effects varies with the plant species, stage, duration and severity of drought. Crop production faces many challenges, due to changing environmental conditions and evolving needs for new plant-derived materials. 
The extreme temperatures those are consequences of present-day global climate changes are considered as major abiotic stresses for crop plants. Temperatures exceeding the limits of adaptation substantially influence the metabolism, viability, physiology, and yield of many plants. Plants exposed to extreme temperatures often show a common response in the form of oxidative stress. However, the extent of damage caused by extreme temperatures depends greatly on the duration of the adverse temperature, the genotypes of the exposed plants, and their stage of growth. Numerous research findings support the notion that induction and regulation of antioxidant defenses are necessary for obtaining substantial tolerance against environmental stress. Plant adaptation to either high temperature or low temperature is a multigenic response which is very complex in nature. Plant response to continuous light depends on plant tolerance and can be modified by alteration in temperature, light intensity, CO2 level, and other environmental factors.

Though the pesticide application represents viable solution to pest control, however indiscriminate use poses threat to target as well as non-target crops. The side effects of pesticides therefore have to be considered based on their use and on the agricultural system to which particular pesticide is used. Studies should be implied on effects and persistence of pesticides in crops and is consequent effects on soil microbial flora and associated nitrogen metabolism. Safe alternate methods like development of relatively cheaper biopesticide should be encouraged. More efficient methods have to be developed and validated for dissipation of pesticide residues in food grains. Human health and environment has gained great importance in the modern world. The widespread use of insecticides has resulted in problems caused by its interaction with the natural biological systems. Study showed that higher amounts of acetamiprid have some negative effects on corn plant physiology. Thus, the use of pesticide should be controlled following the standards of developed countries to protect health and the environment.