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The oilseeds crop occupies an important position in agriculture economy in the world. Indian agriculture has made considerable progress, particularly in respect of food crops such as wheat and rice in irrigated areas; however, performance has not been so good in case of other crops particularly oilseeds, pulses, and coarse cereals. Therefore, after achieving self sufficiency in food grains the government is focusing attention on these agricultural commodities. On the oilseeds map of the world, India occupies a prominent position, both in regard to acreage and production. India is the 4th largest edible oil economy in the world and contributes about 10 percent of the world oilseeds production, 6-7% of the global production of vegetable oil, and nearly 7 percent of protein meal. This sector also has an important place in the Indian agricultural sector covering an area of about 26.5 million hectares, with total production of over 25.3 million tonnes in the triennium ending 2015-16 (GOI, 2016). This constitutes about 14.8 per cent of the gross cropped area in the country. A wide range of oilseed crops is produced in different agro-climatic regions of the country. Insects-pests are one of the limiting factors in the production of oilseed crops. Management of these pest problems by using possible control techniques could increase the quality and quantity of the products. These crops are damaged by a more number of insect pests, of which some are more serious. These pests can be effectively controlled by the integration of different techniques such as use of various safe insecticides/biopesticides, some modification in cultural practices and use of pest tolerant varieties. Integrated pest management approaches will help to increase the production and productivity of oilseed crops by reducing the pest damage without any adverse effect on the agro- system and erosion in the environment. 

Pest wise information of oilseed crop and management of major pests are described below.

India is the largest producer and consumer of pulses in the world, accounting for 33 per cent area and 25 percent production. Pulses are mostly grown under rainfed conditions in marginal to sub-marginal lands. Once a net exporter it is presently one of the largest importer of pulses as our demand outstrips domestic production. While the traditional cropping pattern almost always included a pulse crop either as a mixed crop or in rotation, the commercialization of agriculture has encouraged the practice of sole-cropping. As a result, the annual import has increased from 0.50 million tonnes to 1.80 million tonnes during the last five years and contribution of pulses in the national food basket reduced from 17% to 7%. Pulses are generally grown on marginal and sub-marginal lands under rainfed conditions with low inputs and suffer heavily due to biotic and abiotic stresses, resulting into low productivity. Challenges for pulses in India are decline in area of pulses, low genetic yield potential, low realized yield, instability in production, climate change, biotic and abiotic stresses, poor seed replacement rate, post harvest losses, wide fluctuation in price, no regular MSP/procurement policy, poor availability of critical inputs in productivity zone and poor transfer of technology.

Cereal crops are interchangeably called grain crops. In many publications and correspondence, they are simply called grains or cereals. As of 2012, the top 5 cereals in the world ranked on the basis of production tonnage are rice (paddy), wheat, maize (corn), barley and sorghum. These crops are also among the top 50 agricultural commodities in the world with maize ranking second next to sugarcane. Rice (paddy) ranks third, wheat - 4th, barley - 12^th, and sorghum - 30^th. Another cereal, millet, ranks no. 42 (FAO Stat 2014, updated Aug. 18, 2014). According to Chapman and Carter (1976), “a cereal is generally defined as a grass grown for its small, edible seed.” They also explained that all cereals are angiosperms, monocots, and members of the grass family Gramineae. Similarly, Lantican (2001) defines cereal or grain crops as agronomic crops belonging to the grass family Gramineae or Poaceae which are utilized as staples; the word “cereal” is derived from the most important grain deity, the Roman Goddess Ceres. Among the food grains cereals occupies for most status in human food requirements. Cereals are grown under different agro-climatic (Upland, Low land & Rainfed) conditions and it is most important staple food of about 65% of Indian population. Cereals crop is attacked by a large number of insect pests right from initial to till the harvest of the crops. Brief descriptions of the major crops, major insect pest and appropriate control measures are given below:

Plants are exposed to a wide range of environmental stresses and have to adapt physiologically to these as the local environment changes. Unfavorable soil properties, fertility imbalances, moisture extremes, temperature extremes, chemical toxicity, physical injuries, and other problems are some of the most discussed examples of abiotic disorders that can hamper plant growth which ultimately lead to death of the plants under extreme conditions. Furthermore, many of these abiotic stresses can predispose plants to diseases caused by infectious microbes. These stresses in plants also lead to a series of physiological, biochemical and molecular changes. Impact of biotic stresses on agricultural plants such as wheat, rice, maize, groundnut and many others have been top listed area of interest for researchers but until now, ornamental plants have not been a major object of such studies even though these plants constitute a major part of horticultural production and play an important role in everyday human life.
 
Ornamental plants are an integral part of the urban public places and private gardens. However, these plants are highly sensitive to abiotic stresses, which are known as the most harmful factor concerning the growth and development of these plants. Plant stress implies some adverse effect on the physiology of a plant induced upon a sudden transition from some optimal environmental condition.

India is the second largest producer of vegetables after China with 14 % contribution in total World vegetable production (1160 million tonnes). After the advent of green revolution, more emphasis is laid on the quality of the agricultural product along with the quantity to meet the ever-growing food and nutritional requirements. Both these demands can be met when the environment for the plant growth is suitably controlled. Olericulture a vital component of Indian Horticulture, which includes science and management of vegetables, has made a rapid stride during the last decade, recording appreciable growth in production (162.90 million tonnes against 81.89 million tonnes in 2000-01) and productivity (17.4 t/ha against 12.2 t/ha in 2000-01), availability (210 g/capita/day against recommendations of 300 g/capita/day) and export (36,94,860 tonnes worth Rs. 14,36,487 lakhs.) during 2013-14. Vegetables play a major role in Indian agriculture by providing food, nutritional and economic security and more importantly, producing higher returns per unit area and time (Srivastava et al. 2013). In addition, vegetables have higher productivity, shorter maturity cycle, high value and provide greater income leading to improved livelihoods. The total production of vegetables during 2013-14 was 162.90 million tonnes compared to 21.19 million tonnes in 1960-61, 81.89 million tonnes in 2000-01 and 146.55 million tonnes in 2010-11. Although, olericulture has exhibited leadership role but challenges are much greater. Looking to the requirement, which is estimated to be 225 million tonnes by 2020 and 350 million tonnes by 2030, which has to be produced from declining land and water resources and in the scenario of climate change, the task to meet the needs of growing population would be difficult but not impossible (Singh et al. 2014).

Stress, is usually defined as an external factor that exerts disadvantageous influence on the plant. In most cases, stress is measured in relation to plant survival, crop yield, growth (biomass accumulation), or the primary assimilation processes (CO2 and mineral uptake), which are related to overall growth. Some environmental factors (such as air temperature) can become stressful in just a few minutes; other may take days to become stressful or even months (some mineral nutrients) to become stressful. Different types of abiotic stresses that affect fruit production are; water stress, heat stress, chilling and freezing stress, salinity stress, flooding stress. Although, it is convenient to examine each of these factors separately, many are interrelated. For example, water deficit is often associated with salinity in the root zone/ or with heat stress in the leaves. Plants often display cross resistance, or resistance to one stress induced by acclimatization to another. This behaviour implies that mechanism of resistance to various stresses share many common features.

Plants encounter adverse environmental stresses during their life cycle, which have negative impacts on growth and greatly affect crop productivity. As perennial crops, fruit trees are exposed to an array of stresses for a long time once they are planted. If the trees are severely injured by environmental stresses, it would be hard for them to recuperate, leading to retarded growth and reduced fruit production. Furthermore, the negative effects of the stresses are not limited to the fruit production in the current year but can also extend to the next year(s). Therefore, it is of critical importance to develop techniques for reducing stress injury and/or improving stress tolerance in fruit trees for sustainable cropping, which can be fulfilled by the cultivation method or genetic engineering (Holmberg and Bulow, 1998). 

Pulses belongs to the family Fabaceae (earlier known as leguminosae) comprises more than 600 genera and about 18,000 species of cultivated plants. It is the second largest family after Poaceae (earlier known as Gramineae), in terms of food and vegetable protein source and of fodder. The sub-family Papilionoideae consist of 480 genera and about 12,000 species, of which only a few species are cultivated for human nutrition. Endowed with excellent food and fodder qualities, these crops also restore soil fertility by scavenging atmospheric nitrogen, adding organic matter, enhancing phosphorous availability and improving physical, chemical and biological properties of soil (Graham and Vance, 2003; Dita et al., 2006).

The word ‘pulse’ is derived from latin word ‘puls’ meaning pottage i.e. seeds used to make porridge or thick soup. Pulses or grain legumes in general are indispensible source of supplementary proteins to daily vegetarian diets (Table 1) these are regarded as “poor man’s meat”. Pulse proteins are chiefly globulins and contain low concentrations of sulphur containing amino acids such as methionine and cysteine, but higher concentration of lysine than cereals, pulses provide a perfect mix of essential amino acids with high biological value and also contain higher calcium and iron than cereals.

Soils are the basis of food production. Ninety five percent of our food is directly or indirectly produced on our soil. A healthy soil maintain a diverse community of organisms that helps in controlling pests (insects, weeds, and fungus) but also form beneficial symbiotic association with plant roots, recycle essential plant nutrients and improve soil structure. A healthy soil can also be a strategic ally in mitigating and adapting to climate change, as soil sequesters CO₂ and prevent to escape into the atmosphere. Beside this, it contributes to mitigate climate change by maintaining or increasing its carbon content. This can be said that the proportion of organic carbon is available more in the soil than combining both atmosphere and ground vegetation. Most of the soil organic carbon (SOC) stored in the first metre of the soil in the form of organic matter. However, organic matter degrades due to deforestation; deplete soil biodiversity, loss of nutrients as consumed by crop plants, soil compaction due to excessive use of agricultural machineries, soil erosion, water logging conditions, and urbanization, which release greenhouse gases like CO₂, CH₄, and N₂O into the atmosphere causing global warming and climate change. One third of all CO₂ emissions come from changes in land use (deforestation, shifting cultivation, and intensification of agriculture) whereas two-thirds of CH₄ and majority of N₂O emitted through agricultural practices (Kotschi and Müller-Sämann, 2004).

Agricultural research has been primarily focused to assure food self-sufficiency and security, and little concern on nutritional value “nutritional security” or health promoting qualities of food being produced. Food security has three dimensions, namely: (1) endemic hunger caused by poverty-induced under-nutrition and malnutrition; (2) hidden hunger caused by the deficiency of micronutrients like iron, iodine, zinc and vitamin A in the diet; and (3) transient hunger caused by natural calamities or civilian conflicts. Micronutrient malnutrition is recognized as a massive and rapidly growing public health issue especially among poor people living on an unbalanced diet.
 
Although great progress has been made in reducing the prevalence of hunger, over 805 million people are undernourished in 2012-14, still unable to meet their daily calorie needs for living healthy lives. This number has fallen by 100 million over the last decade (Table: 1 & Table: 2; Source: FAO, 2014). Undernourishment refers to food intake that is insufficient to meet dietary energy requirements for an active and healthy life. About one in nine people go to bed daily on an empty stomach. In cases where food is available, often the quality of the food does not meet micronutrient (vitamin and mineral) needs. More than two billion people continue to suffer from nutritional deficiencies such as vitamin A, iron, zinc and iodine. Despite progress, the number is still high, and marked differences across regions persist. 

Environmental constraints that include abiotic stress factors such as salt, drought, cold, extreme temperatures and heavy metalsalready a major limitingfactor for crop productivity and will soon become even more severe due to climate change conditions.Together, these stresses constitute the primary causes of crop losses worldwide, reducing average yields of most major crop plants by more than 50% (Boyer, 1982; Bray et al., 2000; Wang et al., 2003). Current climate change scenarios predict an increase in mean surface temperatures and drought that will drastically affect global agriculture in the near future (Le Treut et al., 2007).
 
Abiotic stresses trigger many biochemical, molecular and physiological changes and responses that influence various cellular and wholeplant processes (Wang et al., 2001, 2003). For example, drought, salinityand low temperature stress lead to reduced availability of water (alsoknown as dehydration/osmotic stress) characterized by a decreasedturgor pressure and water loss (Dhariwal et al., 1998; Boudsocq and Lauriere, 2005). Osmotic stress promotes the synthesis of the phytohormoneabscisic acid (ABA)which then triggers a major change in gene expressionand adaptive physiological responses (Seki et al., 2002; Yamaguchi and Shinozaki, 2006; Shinozaki andYamaguchi-Shinozaki, 2007).

Crop yields are affected by a combination of abiotic stresses, biotic stresses, and nutritional factors but abiotic stresses (drought, heat, cold or salinity) are the major factors that prevent crops from realizing their full yield potential (Edmeades, 2009). In traditional approach, breeders grow and cross varieties and then evaluate how the progenies vary in their ability to deal with stresses. The best-adapted plants are then selected for growing in fields exposed to stresses. Biotechnologists have taken advantage of recent advances in biotechnology and functional genomics to genetically engineer crops which can give better yield in adverse conditions than the unmodified ones (Manavalan et al., 2009; Umezawa et al., 2006). Drought, extreme temperatures (high or low), high salinity and cold are the major abiotic stresses that affect plant growth and result in significant yield losses. Although plants have evolved a wide spectrum of programs for adaptation to changing environment, the current understanding of the mechanisms associated with the ability of crops to maintain yield under abiotic stress are poorly understood (Witcombe et al., 2008; Munns et al., 2008; Bartels et al., 2005). New advances in ‘omic’ technologies are providing opportunities for identification of transcriptional, translational and post-translational mechanisms and signaling pathways that regulate the plant response. This chapter describers several examples of how modern crop technologies may be applied to broaden crop tolerance of various abiotic stresses and to increase total biomass.

Food productivity is decreasing due to detrimental effects of various biotic and abiotic stresses; therefore minimizing these losses is a major area of concern to ensure food security under changing climate. Environmental abiotic stresses, such as drought, extreme temperature, cold, heavy metals, or high salinity, severely impair plant growth and productivity worldwide. Drought, being the most important environmental stress, severely impairs plant growth and development, limits plant production and the performance of crop plants, more than any other environmental factor (Shao et al., 2009). Plant experiences drought stress either when the water supply to roots becomes difficult or when the transpiration rate becomes very high. Available water resources for successful crop production have been decreasing in recent years. Furthermore, in view of various climatic change models scientists suggested that in many regions of world, crop losses due to increasing water shortage will further aggravate its impacts. Drought impacts include growth, yield, membrane integrity, pigment content, osmotic adjustment water relations, and photosynthetic activity (Praba et al., 2009). Drought stress is affected by climatic, edaphic and agronomic factors. The susceptibility of plants to drought stress varies in dependence of stress degree, different accompanying stress factors, plant species, and their developmental stages. Acclimation of plants to water deficit is the result of different events, which lead to adaptive changes in plant growth and physio-biochemical processes, such as changes in plant structure, growth rate, tissue osmotic potential and antioxidant defenses (Duan et al., 2007 and Shakeel et al., 2011).

Growth and development of plants are dependent upon the temperature surrounding the plant and each species has a specific temperature range represented by a minimum, maximum, and optimum. These values were summarized by Hatfield et al. (2008, 2011) for a number of different species typical of grain and fruit production. The expected changes in temperature over the next 30 to 50 years are predicted to be in the range of 2 to 3°C Intergovernmental Panel Climate Change (IPCC) (2007). Heat waves or extreme temperature events are projected to become more intense, more frequent, and last longer than what is being currently been observed in recent years (Meehl et al., 2007). Extreme temperature events may have short-term durations of a few days with temperature increases of over 5°C above the normal temperatures. A recent review by Barlow et al. (2015) on the effect of temperature extremes, frost and heat, in wheat (Triticum aestivum L.) revealed that frost caused sterility and abortion of formed grains while excessive heat caused reduction in grain number and reduced duration of the grain- filling period. Analysis by Meehl et al. (2007) revealed that daily minimum temperatures will increase more rapidly than daily maximum temperatures leading to the increase in the daily mean temperatures and a greater likelihood of extreme events and these changes could have detrimental effects on grain yield. If these changes in temperature are expected to occur over the next 30 years then understanding the potential impacts on plant growth and development will help develop adaptation strategies to offset these impacts.

Globally, agriculture productivity is challenged by abiotic and biotic stresses, but abiotic stresses in particular (Gong et al., 2013) affect spreading of plant species across different environmental zones (Chaves et al., 2003). The changing climate is expected to worsen abiotic factors globally and adaptation strategies need to be established for target crops to specific environments (Beebe et al., 2011). Connect between different stress factors will likely surge harm to crop yields (Beebe, 2012). Soil salinity is a major environmental constraint to agricultural productivity (Greenway and Munns, 1980; Rhoades and Loveday, 1990). High concentrations of different types of salts, including chlorides, carbonates, and sulfates of magnesium, calcium, potassium, and sodium, characterize different saline soil areas around the world. Moreover, for each type of naturally occurring salinity, constantly changing environmental conditions, such as temperature and precipitation, as well as agricultural practices cause rapid modifications in levels of salinity and salt distribution patterns. Sodium and chloride are the predominant ions in the vast majority of saline areas.

During evolution, various species of plants, known as halophytes, readapted to life in high-salinity environments, but a large majority of plant species grown in non-saline areas are salt-sensitive (referred to as glycophytes). These glycophytic plants, including the majority of crop species, differ greatly in their tolerance to salt stress (Greenway and Munns, 1980; Flowers and Colmer, 2008).

Plants are often exposed to various abiotic and biotic stresses and have developed specific mechanisms to adapt, survive and reproduce under these stresses (Pieterse et al., 2009). Abiotic stresses include drought, water logging, high temperature, cold(low temperature), salinity, chemical pollution (xenobiotics), uv radiation, heavy metal and oxidative and plants are also challenged by biotic stresses through microbial pathogens such as myco-plasma, nematodes, fungi bacteria (Tippmann et al., 2006). The biology of plant cell is more complicated with any foreign stimulus from the environment; multiple pathways of cellular signaling and their interactions are activated. These interactions mainly evolved as mechanism to enable the plant systems to respond to stress with minimum and appropriate physio- biochemical processes. Abiotic and biotic stress induces signals and theses signals are recognized by receptors, followed by generation of secondary messengers e.g. activation of ion channels, production of reactive oxygen species (ROS) Xiong et al., 2002, accumulation of hormones (Bari and Jones, 2009; Peleg and Blumwald, 2011) such as salicylic acid (SA), ethylene (ET), jasmonic acid (JA) and abscisic acid (ABA). Secondary messengers are responsible for modulating intracellular level of calcium, often initiating protein phosphorylation cascade, which may leads to the activation of various proteins directly involved in cellular protection (Tippmann et al., 2006) Fig.1.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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:

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.

Preference of herbicides for weed management in Agriculture and Horticulture

Weeds are unwanted and undesirable plants which interfere with the utilization of land and water resources and pollute atmosphere with their allergic pollen thus affecting human welfare adversely.  They are the plants out of place, growing where we want other plants or no plants at all.  They compete with desirable and beneficial vegetation reducing the yield and quality of the produce.  The effect of weeds in agriculture or horticulture is greatest.  There is a scanty reliable study of worldwide damage to crop yields due to weeds.  Whether the data are available or not, it is well known that losses caused by weeds exceed the losses from any category of agricultural pest, viz., insects, nematodes, diseases, rodents etc. Weeds account for 45% while insects 30%, diseases 20% and other pests 5% of the total annual loss of agricultural produce186.

Introduction

India has a big challenge in fruit production in the current backdrop of decreasing per capita land holding and static fruit productivity. In recent years, China has surpassed and secured top position in the fruit production in the world accounting for 4,44,651 mt production followed by India and Brazil.  Now Chinese share in the fruit production is around 13 per cent while India contributes 10.2 per cent, Brazil 8 per cent and USA 6 per cent of total fruit production.

India is bestowed with a wide variety of agro-climatic conditions and enjoys an enviable position in the horticultural map of the world. Almost all types of fruit crops (tropical, sub-tropical and temperate) are grown in one or other part in the country.  The major tropical and sub-tropical fruits grown in India include mango, banana, papaya, orange, mosambi, guava, grape, pineapple, coconut, sapota, ber, pomegranate, litchi, aonla, bael, jackfruit etc.  Cashew nut cultivation has a big potential and its production, productivity and export has increased significantly in recent decades. Indian grape has recorded highest productivity per unit area in the world. The productivity of fruit per unit area in India has increased nearly from 10 t/ha to 12 t/ha in almost one decade.  However, the average productivity in most of the fruit crops is far below than satisfactory except grape and banana in few states.  It is paradox to record that India’s contribution in the overseas market is almost (0.11 per cent) negligible (Chadha, 2000). However, other countries like Mexico, Philippines and Venezuela, which produce far less, export 4 per cent of their total production.

Introduction

To keep pace with the ever-increasing demand for crop yield by the exploding population, use of chemical fertilizers and pesticides in agricultural production has become indispensable.  Production cost of agriculture has skyrocketed owing to the abandoning of green, organic farmyard manure and use of chemicals. However, the problems associated with chemical pesticides are abundant. The excessive application of chemical fertilizers causes soil sealing, fertility diminishing and residual problems. The leftover chemical fertilizers and pesticides have seriously affected the quality of agricultural products, people’s health and caused environmental pollution.  The over use of fertilizers has also damaged the soil’s original micro-ecological balance and deteriorated the diseases spread by soil.  While some pesticides must be abandoned because of their unacceptable non-target effect, there will always be a need in agriculture for safe and selective chemicals to limit the effects of pests.  More significantly, it is becoming increasingly more difficult and expensive to find new kinds of synthetic chemical pesticides.  Implications of chemical pesticides in ecological, environmental and human health problems have increased public awareness and concern regarding the continued use of agrichemicals that are damaging to human or  environmental health thereby obviating the search for effective alternative approaches which have minimal deleterious effects, more environmentally friendly, and will contribute to the goal of sustainability in agriculture.  In this line Plant growth-promoting rhizobacteria (PGPR) present immense potential and promise as effective substitutes for chemicals.  PGPR enhance plant growth and survival, control soil-borne fungi, and induces systemic resistance to phytopathogens and is used as inoculants for biofertilization, phytostimulation and biocontrol.

Introduction

After water, nitrogen is the most critical nutritive element for crop productivity and human efforts to produce food and energy have greatly changed the nitrogen cycle of the earth. Sustainable cropping systems throughout history and across the world have relied on the combination of a cereal with an N-fixing legume. In recent history, cereals have dominated global agriculture, while legume areas and productivity have stagnated or even declined. An atmosphere around us contains nearly 78% nitrogen, which is in free form. Hence it is not available to plants. At present, India produces around 206 million metric tones of foodgrains for its growing population, increased foodgrain cannot be produced unless we carefully make use of biological nitrogen. Biological nitrogen fixation is the key to sustain agricultural productivity through the application of biofertilizers in the field. However, there is an urgent need to transfer this technology on the field to farmers and industry by producing these fertilizers on large scale.

INTRODUCTION

One of the most dangerous ecological crises being faced by all living organism now-a-days is the pollution of the environment. It is easier to describe pollution rather than to define it. It is presumed that the environment in past was more or less pure. But due to various activities of man such as industrialization, urbanization, agricultural practices etc, composition of the environment gets changed which is called environmental pollution. Any substance that creates pollution is called ‘pollutant’. There are different types of pollution among which pollution caused by toxic level of heavy metal pollutants is called heavy metal pollution.

Heavy metal pollution is a problematic field of research and is gaining immense importance now-a-days. We have 104 elements in the periodic classification of which 80 are metals. According to Passow et al. (1961), heavy metals are those having densities more than five (5 g cc^-1) and atomic weight twenty three. The term ‘heavy metal’ is imprecise but is widely used although others such as ‘toxic metal’, ‘trace element’ are possible alternatives. Sources of these heavy metals are varying; some of these are encountered in water, air effluent, solid waste and sewage. They are emitted out from various sources e.g. waste water from electroplating industry (Cr, Ni), air emission from fluorescent lamps (Cd, Be), paint pigment waste (Pb, Cr), auto-exhaust emissions (Pb, Te) etc.

INTRODUCTION

The purpose of writing this chapter is to develop a comprehensive understanding of the role of functions of water in plant growth and development. Water is essential to life on earth as the living organisms contain 80-90 per cent water. A typical crop or grassland will transpire approximately 500 ml of water per 10 g of dry matter produced. Water has a tremendous effect on the environment near the earth, which on regional basis we call ‘climate’. Ecological importance of water is due to its physiological importance because water affects the plant growth through physiological processes. All metabolic activities in the plant cell or tissue depend on water status of the plant. For example, in a maturing seed, respiration rate is highest as it moves towards maturation stage, water content decreases and hence rate of respiration slow down. At the harvesting stage, when the water content is 10-20%, the respiration rates become negligible. Now in a stored seed if the water content will be high it will result into higher respiration, thus release energy, which will increase the temperature and will finally destroy the seed.

INTRODUCTION

Among plant nutrients, our soils are particularly low in nitrogen and therefore, require is high doses of nitrogenous fertilizers for getting optimum productivity. Added to this is the problem of poor efficiency of nitrogeneous fertilizers which under normal conditions is only 40 – 50 %, still less for rice ranging from 25 – 35 %, and the residual effect for the succeeding crops is never more than 10 %. The rest of the applied nitrogen is lost either through volatilization, leaching or denitrification (Kashyap, 1978). The high cost of nitrogenous fertilizers and their poor utilization efficiency very much add to the high cost of cultivation. Hence, the need of the hour is to decrease our dependence on chemical fertilizers and increase the efficiency of the fertilizer thus used. The increase in nitrogen efficiency in crop plants can be achieved by reducing denitrification with the use of nitrification inhibitors, reducing the soil compaction, improving drainage conditions, use of soil improving crops, and adopting carefully the irrigation procedures (Carlson, 1980). No doubt exploration of this possibility is a big task, nevertheless, the understanding of physiology and biochemistry of nitrogen nutrition at molecular level is obligatory and is likely to add insight to achieve the hard task goal.

INTRODUCTION

The metabolism of carbohydrates is vital for plant growth and development, and to the yield of major plant products such as starch and sucrose. Starch, sucrose and fructose are the three important carbohydrates which are utilized in most of the higher plants. The majority of sucrose that is synthesized in higher plants during photosynthesis is exported to non-photosynthetic cells (ap Rees, 1992). Starch serves as an important storage for carbohydrate residues. The degradation (breakdown) of starch ensures retaining of important life processes in plants when there is carbon shortage, for instance, during night period in leaves or in resting organs such as potato tubers.

Phospholipids are the most abundant lipids of biological membranes. They serve primarily as structural components of membranes and are never stored in large amounts. As the name of phospholipid implies, this group of lipids contains phosphorus in the form of phosphoric acid groups. The major phospholipids found in membranes are the phosphoglycerides (phosphatides) (Fig.1). Which have two fatty acid molecules esterified

INTRODUCTION

Iron in the terrain’s crust is more oxidized now than it was when life evolved. It has been hypothesized that dissolved ferrous iron could have been a convenient oxygen acceptor and that deposition of oxidized iron in sediments must have taken place before oxygen could have entered the atmosphere in significant quantities. Obviously, during early evolution on this planet, the essential elements are present only in reduced form. Today a number of elements are present only in a highly oxidized form and considerable energy must be expanded to reduce them to a form similar to that on early earth which plants can utilize.

Iron represents essential elements which are usually available in oxidized form but must be reduced, often using metabolic energy, before they can be utilized. For the first time, Gris (1844) observed yellowing of grapevine leaves in absence of iron in the nutrient solution in which these plants were growing. Later, iron was reported to be essential for diverse group of plants. Due to a great variation in iron requirement by different plant species, it is difficult to decide whether iron is a macro or micronutrient.

Introduction

Salinity is a significant environmental stress for crop plants it account for about 70% of the losses in the crop yield. It adversely affects seed germination, seedling growth and different metabolic activities in plants (Begum et al. 1997). It reduces DNA, RNA and protein synthesis and differentially influences the activities of the hydrolytic enzymes (Kumar et al. 1996).

Plants are classified as glycophytes or halophytes according to their capacity to grow on high salt medium. Most crop plants are glycophytes and cannot tolerate salt stress. High salt concentration decreases the osmotic potential of soil solution creating a water stress in plants. Secondly they cause severe ion toxicity since Na+ is not readily sequestered into vacuoles as in halophytes.

The widespread nature of saline soils compounded by the geographical distribution of man’s population and agricultural practices are largely succeeded in increasing salinization in arid and semi-arid lands. Most of the crops are sensitive to even low concentration of NaCl.

Introduction

Chickpea, the world’s third most important food legume, is currently grown on about 10 m ha worldwide, with 95% cultivation in the developing countries. India is the largest producer of chickpea in the world. Chickpea is grown under rainfed conditions in winter in India subjecting it to abiotic stresses. Consequently it experiences water deficit stress at one or the other growth stage(s) which affects the crop productivity.  Among the abiotic stresses to which chickpea is subjected to drought stands to be the number one problem in major chickpea growing regions because the crop is grown on residual moisture and the crop is eventually exposed to terminal drought (Johansen et al., 1994). A distinctive variation exists between the plant in sensitivity to water stress. Chickpea is considered relatively more tolerant, possibly because of its deeper root system is and its smaller leaves and canopy. Several adaptive mechanisms are evoked by plants in response to water stress (Chaves et al., 2003). These traits enable chickpea to ensure its survival in different environmental conditions.

Introduction

It is an established fact that water in terms of direct deficit (drought) as well as water surfeits (flooding and water logging) and poor irrigation water quality (salinity)- are major constraints on the use of solar energy for food, feed and fiber production in almost all the agricultural regions of the world. The various biophysical, physiological, genetic, agronomic and ecological aspects of plant water relations have been thoroughly reviewed in recent years with the objective aimed at water availability as a constraint on crop production. This review will attempt a limited synthesis of these aspects, drawing mainly from research on drought resistance in grain crops, rice in particular, and emphasizing the progress- theoretical and practical- that could result from collaboration between physiologists, geneticists and plant breeders. A central theme will be research and development aimed at fitting crop plants to fluctuating drought prone environments. It is noteworthy that shortage of water restricts crop productivity all over the world-not just in those areas classified as arid or semiarid, but in any area in which the evaporative demand exceeds rainfall during the growing season. As such, the interaction between genotype and environment in situations has an important bearing affecting the physiology and also biochemistry at cellular level vis-à-vis the crop phenology. Cultivars with better ability to access soil water and improved water use efficiency could increase yields in an economic and environmentally sustainable way.

Introduction

The study of abiotic stresses in plants has advanced significantly in recent years. However, the majority of experiments testing the response of plants to changes in environmental conditions have focused on a single stress treatment applied to plants under controlled conditions. In contrast, in the field, a number of different stresses can occur simultaneously. These may include conditions such as high irradiance, low water availability, extreme temperature, or high salinity and may alter plant metabolism in a novel manner that may be different from that caused by each of the different stresses applied individually. The response of plants to abiotic stresses in the field may therefore be very different from that tested in the laboratory (Cushman and Bohnert, 2000).

Introduction

The phytohormone abascisic acid (ABA) was discovered in connection to studies related to shedding of fruits and leaves, also called abscission, and the dormancy of buds. It was first identified and characterized by Frederick Addicott and his associates in 1963 while studying the compounds responsible for the abscission of cotton fruits. Inhibition of growth and maintenance of the dormancy of buds are the most important visible effects of ABA. The concentration of ABA does not remain constant as its concentration decreases in the buds significantly after sprouting and rises during seed and fruit production. Its concentration in dormant seeds is very high and considered as an efficient inhibitor of germination. The role ABA plays during the abscission of fruits and leaves is not clearly understood as its effect is very clear in case of fruit abscission where as it is not very clear on the abscission of leaves. However, the regulatory effect of ABA on the water balance is established in plants. It also induces stomatal closure to inhibit further loss of water. Being a growth inhibitor, ABA also reverses the effect of growth-stimulating hormones like auxin, gibberellins and cytokinin in different tissues of a plant. One of the main goals of phytohormonal ecology is to study the interactions between biotic and abiotic stress at hierarchical levels of biological organization.

Introduction

There are a number of chemicals in the environment, some natural other man-made, some toxic other non-toxic. These are toxic chemicals, whether natural or man-made, which has created problems for the environment and biota on the earth. Of these toxic chemicals, heavy metals are extremely hazardous. Metals are present naturally in the earth’s crust at various levels. However, increasingly widespread heavy metal pollution resulting from anthropogenic activities has caused serious environmental problems and is posing threat to both wild life and human population (Nriagu and Pacyna, 1988). Natural sources include weathering of mineral and metal ions from rocks, displacement of certain contaminants from groundwater or subsurface layers of soil, atmospheric deposition from volcanic activity, and transport of dust. The anthropogenic sources include deposition of industrial effluents, application of sewage sludge, deposition of air-borne industrial wastes, military operations, mining, landfill operations, use of agricultural chemicals, gas exhausts and energy and fuel production (McIntyre, 2003).

Introduction

The term ‘lectin’ was coined by William C. Boyd in 1954 for their property of selectivity (Latin ‘legere’, to pick up or choose). In 1888 H. Stillmark of Russia gave the first description of what we now know as lectin. While investigating the toxic effects on blood of extracts of the castor bean (Ricinus communis), Stillmark observed that the red blood cells were being agglutinated by a protein and gave it the name ‘ricin’. Shortly afterward ‘arbin’ was extracted from Arbus precatorius. Because they were first isolated from plants, lectins came to be known as phytohaemaglutinin. Now it has become clear that lectins are present not only in plants but also in some bacteria, vertebrates and invertebrates. However, lectins are most widely distributed in plants, reported in almost 1000 plant species.

Plant lectins are a very heterogeneous group of proteins; as far as their occurrence within the plant kingdom and distribution over tissues are concerned. They show high degree of heterogeneity with respect to biochemical and physiological roles, because of their widely different carbohydrate binding specificities (Etzler 1986; Rüdiger 1988; Goldstein and Hayes, 1978). Besides the fact that they all exhibit carbohydrate binding activity, most of the plant lectins behave as typical storage proteins (Peumans and Van Damme, 1995 b).

Introduction

Phenolic compounds have been shown to be of importance in regulation of plant growth, development and metabolism, therefore now they are not considered as passive by products of any catabolic or anabolic processes. Salicylic acid is one of them and it is a naturally occurring phenolic which has received much attention due to its association with economically important plant responses to disease and other stresses (Raskin, 1992; Borsani et al., 2001; Clarke et al., 2004). Centuries before medical scientists had identified numerous therapeutic effects of salicylates. Leaves and barks of willow tree were used by women as a pain reliever during child birth in 4th century B.C. It also cured aches and fevers. Due to a number of curative properties of willow bark, in 1828 Jahann Buchner, a scientist from Munich had isolated a small amount of silicin - a salicylic alcohol glucoside, the major salicylate in willow bark. In 1838, Rafaela Piria had given the name salicylic acid (SA), from the Latin salix, a willow tree. Further during 19th century SA and other salicylates, mainly methyl esters and glucosides easily convert to SA, isolated from a number of plants. Salicylic acid has an aromatic ring which bears a hydroxyl group or its functional derivative (Fig. 1).

Introduction

The respiratory electron transport pathway of plant mitochondria comprises the cytochrome (Cyt) pathway and alternative pathway (McDonald et al., 2002). Both the cyt and the alternative respiratory pathways start at protein complex I when NADH is being oxidized. One H+ (proton) is transported by the complex I to inner membrane space, whereas two electrons are transported within the inner membrane by the ubiquinone, which at its reduced state (Qr) transfers these electrons either to complex III or to the Alternative oxidase (AOX). Ubiquinone is the point in which reactions can proceed in different ways, and it is called the branch point. Cyt respiratory pathway is present in all living organisms. It proceeds while complex III pulls out a proton from the mitochondrial matrix to the inter membrane space. The electrons are received by cytochrome c which spreads up to the outer side of the inner membrane towards protein complex IV, which then pulls out another proton similar to complexes I and III, and transports the electrons back to inner domain of the mitochondria. As a result, oxygen is consumed with a proton and the two electrons to produce water (Fig 1).

Introduction

Seed, the basic input of crop production technology, is exposed to various stress factors right from its formation to the completion of its germination. Even after germination, the stressed seeds may fail to emerge into a healthy plant and thus, the subsequent seed formation is also affected both quantitatively and qualitatively.

The stress factors may be abiotic, biotic or mesobiotic. Environmental factors such as climatic parameters, nutritional deficiencies, soil factors and conditions of storage are the examples of abiotic stress factors. Insects, fungi, bacteria, nematodes and other plant parasites constitute biotic stress factors whereas viruses, viroids and virusoids and similar agencies are the examples of mesobiotics factors that bring about stress over the seed. Apart from these conspicuous causes of stress, there are certain other factors also, which may affect the influence of stress over the total performance of the seed. For example, the crop improvement efforts bring about changes in seeds quality that can have considerable effects on the vulnerability of the seed to invasion by various biotic factors.

Introduction

The life cycle of a plant passes through biotic and abiotic stresses and plants are being attacked at different stages of growth by a number of disease causing organisms. These organism including bacteria, fungi, viruses, and nematodes attacks plants. These pathogens caused large crop losses and probably since the beginning of agriculture have contributed to human hunger and malnutrition. The control of plant diseases is thus of fundamental importance and is a major objective of plant breeding and pathology programme and agriculture chemical industry. Plants resists pathogens attack both with preformed defenses such as antimicrobial secondary compounds and by inducing defense responses (Hammond and Jones, 2000, Heath, 2000). Inducible defenses can be activated upon recognition of general elicitor such as bacterial flagellin and even host cell fragments released by pathogens damage (Gomez and Boller, 2000, Hammond and Jones, 2000). However, plants also involved sophisticated recognition systems to detect proteins produced during infection by specific races of pathogens (Martin et al., 2003).

Introduction

Plants are responsive to the applied Non-scheduled caste, which constitute most of the vital macromolecules and metabolites related to its vegetative and reproductive cycle. The applied fertilizer N enhances crop productivity per unit area, as agricultural soil deficient in N worldwide. The fertilizer application is thus considered essential to meet the requirement of the burgeoning population, particularly in the developing countries (Abrol et al., 1999; Chanda and Sati, 2005). The farmers practicize heavy dressing of N-fertilizers in crop fields for high productivity, which has resulted into world including Indian sub-continent and China have resulted into the excessive use of N-fertilizers intending to maximize crop yield. Decrease in the organic fertilizer input and depletion of micronutrients in intensive cultivation zones have caused a decline or stagnation in the crop productivity, which  has been attempted with a further loading of soluble chemical fertilizers (Maleshwar, 2003; Kumar and Yadav, 2003; Anonymous, 2004; Chanda and Sati, 2005; Abdin et al., 2006).

The word cell was coined by Robert Hooke with the help of compound microscope. Cell is the basic unit of life. A plant cell has three distinct components a). Cell wall b). Protoplasm and c). Vacuole. Cell wall  and  vacuole are considered as non-living substances. The protoplasm which is living is  composed of 1. Cytoplasm and 2. Nucleus. The cytoplasm contains several organelles such as mitochondria, chloroplast, ribosomes, endoplasmic reticulum, golgi complex, lysosomes, plastids etc.