eChapters

A. Anther and Pollen Culture (Production of Haploid Plants)

Haploid plants possess a single set of chromosomes (gametophytic no of chromosomes i.e. n) in the sporophyte in contrast to diploids which contain two sets of chromosomes (2n). The existence of haploid plants was reported by Bergner (1921) in Datura stramonium. Guha and Maheswari (1964) reported the direct development of haploid embryos and plantlets from microspores of Datura inoxia by the cultures of excised anthers. After this, haploid plants have been produced via anther culture in more than 170 species. The anther culture technique is useful in haploid production.

Experiment - 1
 
Aim: Micropropagation of Tobacco plant by leaf disc culture

Principle: The totipotency of the plant cells and tissues form the basis for in vitro cloning i.e., generation or multiplication of genetically identical plants in in vitro culture. The ability to propagate new plants from a cells or tissues of parent plant has many interesting possibilities.

Micropropagation /Clonal propagation

Micropropagation or clonal propagation is the growing of plants from meristematic tissue or somatic cells of superior plants on nutrient suitable media under controlled aseptic physical conditions. Sexually propagated plants (through generation of seeds) demonstrate a high amount of heterogeneity since their seed progenies are not true to type whereas asexual reproduction (by multiplication of vegetative parts) gives rise to genetically identical copies of parent plant. Thus, it permits perpetuation of the parental characters of the cultivars among the plants resulting from micropropagation. Micropropagation proves useful for propagation of: 

Modes of Culture 

Callus is a mass of undifferentiated plant tissues formed from plant cells or tissue cuttings when grown in culture. Tissues and cells of plant cultured in a liquid medium aerated by agitation grow as suspension of single cells and cell clumps. For growth, the cells require to divide, whereas, the cells breaking up from explant are mature, nondividing. Hence, the differentiated tissue undergoes modifications to become meristematic. This phenomenon of a mature cell reverting back to meristematic state to form undifferentiated callus tissue is called dedifferentiation.

Explant

The tissue obtained from plant to be cultured is known as Explant. It may include the parts of shoots, leaves, stems, roots, flowers and callus.

Maintenance of Aseptic Environment

All culture vessels, media and instruments used in handling tissues as well as the explants must be sterilized. The importance is to keep the air surface and floor free of dust. All operations are carried out in laminar air-flow, a sterile cabinet.In general, the methods of elimination of these sources of infection can be grouped under different categories of sterilization procedures: 

Sterilization Techniques

Sterilization: All the materials, e.g., vessels, instruments, medium, explants, etc., used in culture work must be freed from microbes. This can be achieved by one of the following approaches:

One of the most essential factors governing the growth and morphogenesis of plant tissues in culture is the composition of the culture medium. The basic nutrient requirements of cultured plant cells are very similar to those of whole plants. The basic nutritional requirements of cultured plant cells as well as plants are very similar. However, the nutritional composition varies according to the cells, tissues, organs and protoplasts and also with respect to particular plant species.  The appropriate composition of the medium largely determines the success of the culture. A wide variety of salt mixtures  have been reported in various media. A nutrient medium is defined by its mineral salt composition, carbon source, vitamins, plant growth regulators (PGR) and other organic supplements. When referring to a particular medium, the intention is to identify only the salt composition unless otherwise specified. Any number and concentration of amino acids, vitamins, growth regulators and organic supplements can be added in an infinite variety of compositions to a given salt composition in order to achieve the desired product.

Common rules for fine laboratory techniques call for:

    ·    A laboratory should have a record and a complete up to-date record of all the equipments and their operating manual.
    ·    A laboratory should have a record and detailed up to-date record of all the chemicals including the name of manufacturer with their     grade and arranged alphabetically in specific area
    ·    Strong acid and bases in safe area.
    ·    Chloroform, alcohol which are volatile or toxic must be stored in fume hood.

A tissue culture laboratory can be placed in any geographical area. The internal controlled environmental conditions permit isolation with a minimum of external influence. To decide where to build the tissue culture laboratory, the following factors must be taken into consideration:

Year    Contributor    Description
1756    Duharmel du Monceau H.L.    Discovered callus formation in decorticated elm tree. 
1839    Schwann, T.H.    Proposed the view that each living cell of a multicellular organism would be capable of developing independently if provided with proper external conditions.
1853    Trecul, A.    Performed experiment on callus formation by decorticated trees such as Robinia, Pawlonia and Ulmus.

Practical have a significant role in the study of any theoretical subject. Whatever a student learns in theory, he verifies it by actual doing with his own hands.  Thus, these reduce any doubts and misbelieve from his mind. These verifications by actually doing the things are performed in the laboratories.  A laboratory is a place with the basic and essential equipments and adequate facilities for students and teachers to perform and observe experiments.  Plants will continue to provide novel products as well as chemical models for new drugs in the coming centuries.  The arrival of chemical analysis and the characterization of molecular structures have helped in precisely identifying these plants and correlating them with their activity under controlled experimentation.

For seed storage in the gene banks, the seed stored should have high quality which is greatly affected by seed handling during collection. The details on these issues have been given by Smith (1995).  In terms of seed storage characteristics seeds are of following 3 steps.

11.1 Introduction

The laws governing the flow of water in wells are referred to as the hydraulics of wells. Just like surface water flows from a higher elevation to a lower elevation by gravity, groundwater also flows from a region of higher water table to a region of lower water table. This difference of water table measured by any two piezometers divided by the longitudinal distance between them is called as hydraulic gradient. Hydraulic gradient plays a dominant role in deciding the flow of groundwater. This hydraulic gradient together with the hydraulic conductivity of the aquifer material forms the main law of well hydraulics called as Darcy’s law. An understanding of Darcy’s law together with some other laws as discussed subsequently in this chapter is essential in order to know the discharge of a well in a particular formation. Darcy’s law is valid for studying groundwater flow in alluvial formations. However, it is not valid for aquifers having hard rock areas.

10.1 Introduction

During rain or heavy irrigation, a part of the rainfall or irrigated water moves below the effective root zone of the crop which moves further below and adds to the water table lying above the impermeable bed or hard rock which is called as  ground  water  reservoir. At  times  the  accumulated  surface  water  is  also recharged to the soil reservoir both naturally as well as artificially that add to the underlying ground water reservoir. This groundwater is an important source of water for irrigation as well as domestic uses. It is the most abundant fresh water resource of the earth. Underground water reservoirs contain large stock of fresh water resources. Total quantity of groundwater within 800 m distance below  the  ground  surface  is  more than  30  times  the  total  water  in  all fresh water lakes, more than 60 times the total water in soil and other unsaturated rock materials, more than 300 times the water vapour in the atmosphere and 3000 times the average volume of all rivers and rivulets in the world (Lenka, 2001). But the distribution of groundwater is not uniform.

Abstract

Ectomycorrhizal symbionts are important natural resources to revive degraded and deforested areas. Artificial inoculum of these mycobionts improves the growth of tree seedlings in nutrient poor soils due to the formation of extensive network of fungal mycelium responsible for the transfer of water and nutrients to the plants. Seedlings of tree species like, Pinus insularis, Quercus griffithii and Schima wallichii with ectomycorrhizae formed by Suillus bovinus, Boletus edulis and Scleroderma citrinum were studied in field condition. The study was conducted at two different stages of degraded sites. Results of the study indicated that seedlings with ectomycorrhizae were able to generate numerous lateral roots of greater length and thereby utilize water and nutrients more effectively than non- mycorrhizal ones The degree of mycorrhizal development varied in different host species with different fungal species. There was a strong relation between the colonization by mycorrhiza and the survival of seedlings. The study has suggested that mycorrhiza has a potential in reclamation of soil and reforestation of degraded land. S. bovinus., B. edulis and S. citrinum successfully colonized and promoted the growth of P. insulates Q. griffithii and S. wallichii respectively in reforestation programmes of degraded lands of Nagaland.

Abstract

The word “mycorrhiza” literally means “fungus root” to describe the mutualistic association between roots of higher plants and certain fungi. Arbuscular mycorrhizae (AM) are the most common and widely occurring of all the mycorrhizal associations and have great economic significance. They belong to the phylum Glomeromycota. Mycorrhizal associations are potential factors in determining the diversity in ecosystems. They can probably modify the structure and functioning of a plant community in a complex and unpredictable way. Currently there is considerable resistance against the use of chemical pesticides and fertilizers, because of their hazardous influence on the environment, and on soil, plant, animal, and human health. Hence, use of biofertilizers and biocontrol agents are recommended in practical agriculture/horticulture/forestry.

Abstract

Photosynthetic blooms of toxin producing marine algae are often referred to as “red tides”. Proliferations of freshwater toxin-producing cyanobacteria are simply called “cyanobacterial blooms” or “toxic algal blooms.” Biotoxins of cyanobacteria are water-soluble and heat stable and they are released upon aging or lysis of the cells. The primary types of cyanobacterial biotoxins involves three types of toxins: hepatotoxins (microcystin; cylindrospermopsin and nodularin), which are taken up by the liver and cause weakness and anorexia (loss of appetite); neurotoxins (usually anatoxin and saxitoxin), which effect the nervous system and dermatotoxins (aplysiatoxin and lyngbyatoxin, LPS), which cause skin and mucous irritations upon contact. Unlike freshwater toxic algal blooms, marine algal toxins become a problem primarily because they may concentrate in shellfish and fish that are subsequently eaten by humans, causing syndromes known as paralytic shellfish poisoning/PSP (paralysis due to saxitoxin and gonyaulatoxins), diarrhetic shellfish poisoning/DSP (diarrhea due to okadaic acid) , amnesic shellfish poisoning /ASP(memory disturbances due to domoic acid), neurotoxic shellfish poisoning/NSP (paresthesia due to brevetoxin; also bronchial spasms). Coral reef fishes are the vectors of another algal poisoning, the ciguatera fish poisoning/CFP (paresthesia, warm-cold sense inversion etc., due to ciguatoxins and maitotoxin).

Abstract

The traditional forage production systems and grazing lands are under extreme pressure due to the population growth of both human and livestock, decreasing area and inputs. In the central India, especially the Bundelkhand region, the soil is highly weathered, degraded and have low inherent nutrient, which was further worsened due to use of chemical fertilizers and pesticides, for enhancing crop production to meet the escalating demand of the population.

Abstract

Microorganisms that harbour in the root region are the most befitting candidates for use as biocontrol agents. The rhizosphere provides the frontline defense for root against attack by pathogens. Pathogens face a complicated phenomena of antagonism from roots. They also compete with each other for site of colonization on the root surface and plant nutrients. The ideal biocontrol agent introduces and /or promotes the antagonists only, whenever required and are most effective in minimizing the wasteful application of inoculum to non-targets. Many genera belonging to bacteria, fungi, actinomycetes and viruses are used as biocontrol agents to combat several important plant diseases. The present review focuses on the use of bacterial antagonists ,particularly rhizobacteria, as biocontrol agents of fungal diseases of plants , their mechanism of action, molecular and genetic basis of antagonistic property and possible genetic manipulations to bring about desirable changes. 

Abstract

Extensive occurrence of alkaline soils has been reported from the Indo-Gangetic plains of Northern India, which is commonly known as ‘usar’ or ‘reh’. High alkalinity and high exchangeable sodium percentage (ESP) of such soil render it inhospitable for normal crop production. Research efforts over the past few decades have resulted in evolving a number of practices for the reclamation and management of such soils. However, application of biological inputs in combination with some moderately salt tolerant plant species seems to be a better option. AM fungi is well known to enhance the ability of plants to cope with environmental stresses generally prevalent in the degraded ecosystems and stress conditions by providing a number of nutritional and non-nutritional benefits. Since isolates of AM fungi differ in their tolerance to adverse physical and chemical conditions in soil and are better adapted to their native stressed microhabitat, selection of appropriate native AMF isolate is necessary for any large scale reclamation program. Taxonomic diversity of AM fungi in the alkaline soils of Upper Gangetic plains of district Allahabad and adjoining areas has been investigated and it was found that such soils have a detrimental effect on the AM spore population, distribution and diversity. Maximum spore population occurred in winter and minimum in summer. Glomus followed by Acaulospora was the most dominant genus. Acaulospora scrobiculata and Glomus fasciculatum were the most frequent species followed by Glomus mosseae and Glomus aggregatum. Glomus fasciculatum was the most abundant species followed by Glomus mosseae and Acaulospora longula.