eChapters

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.

Abstract

Complex industrial wastewater by using conventional treatment method is a significant challenge for its safe disposal. Recently, two step treatments by aerobic bacteria using activated sludge process followed by rhizofiltration has been recommended as a promising technology for detoxification of complex industrial waste. In activated sludge process recalcitrant compounds are biotransformed along with biodegradation of organic waste. Aerobic treatment may be activated sludge process, trickling filter or aerobic lagoon process, which one is used for treatment  it is based upon the characteristics of wastewater. Carbon and nitrogen ratio along with other organic compound is also play important role for microbial growth and degradation of pollutants. During degradation of various pollutants, metal microbes interaction play significant role for its bioremediation either through adsorption or bioaccumulation.

Abstract

The potent greenhouse gases N₂O and CO₂ are relased by aerobic/anaerobic respiring bacteria, archaea, fungi and protists in increasing amounts from converting virgin rain forest and permafrost soils, over fertilized agricultural fields and grasslands including animal husbandry, compost/waste water treatment plants, oceans, savannahs, forests of the temperate climate zones in annual amounts of 0.5 to 4.2 terragrams (Tg) N₂O-N into the atmosphere after autotrophic and hetreotrophic NH₄⁺ to NO₃- oxidation. With estimated 0.25% industries contribute to the annual atmospheric N₂O-N concentration increase.

Abstract

Understanding the impacts of organic or inorganic nutrient management on soil biology and biochemistry may help to develop more sustainable fertilization strategies. The results from comprehensive study made on a field experiment comparing the long-term (more than 100 years) effects of organic manures and inorganic chemical fertilizers on soil biological and biochemical properties are reviewed. The soils adopted with three nutrient managements viz., no fertilization (control), inorganic chemical fertilizers (IC) and organic amendments (OM) obtained from long-term fertilizer experiment were assessed for physical, chemical, microbiological and biochemical properties in three successive years. The response of most of the assessed soil variables to long-term organic nutrient management was significantly higher than those from inorganic fertilization and control (OM > IC = control).

Abstract

Microbial inoculants are low cost inputs with high benefits in agriculture. Solid carrier based (peat or lignite) inoculants are used in most tropical countries. The carrier based inoculants have short shelf life, are liable to have high contaminants and have shown inconsistent field performance. In recent years, special liquid formulations containing not only the desired microorganisms and their nutrients but also added cell protectants or chemicals that promote formation of resting spores or cysts have been developed. The liquid formulations have longer shelf-life (12 months at room temperature) and are also more tolerant to adverse conditions encountered in storage. Liquid Rhizobium biofertilizers enhanced the soybean crop yields in the United States of America, Brazil, Europe and Asia over carrier based inoculants.

Abstract

Discovery of the agricultural utility of microbes during the later part of the eighteenth century, led to the formulation and utilization of superior microbial strains as biofertilizers, for a wide variety of crops and growing conditions across the world. Though microbial inoculants have been in usage for almost two centuries, they are yet to capture the collective imagination of farmers across the globe, which is essential to meet the larger objective of reducing chemical input usage in cropping systems. One probable reason for this is the existence of large growing tracts that are subject to various abiotic stresses of atmospheric and edaphic origin, which limit the proliferation and efficiency of the microbial strains that are commonly used in inoculant production.  This is obvious, since unlike chemical fertilizers, microbial cells being living systems need to grow and thrive in the introduced eco-systems in order to achieve the desired effects of inoculation. But unfortunately microbial inoculant technology has largely adopted the one size-fit all mindset, which had led to failures of microbial inoculants especially in abiotically stressed growing environments. In such a scenario it would be wise to adopt a location or region specific approach for the selection of superior and locally adapted microbial strains for inoculant production.

Abstract

Soil microorganisms play a major role in the biodissolution of nutrients bound in the soil silicate minerals. Plant nutrients like K, P, Ca, Mg, Fe, Zn, and Mn are bound in them. Silicon is considered as agronomically important as it confers rigidity and strength to crop plants and enhances yield. Biodissolution of these nutrients result in their availability to crops influencing the growth, biomass and yield. The microbial metabolites like organic acids, amino acids, inorganic acids, amines, ammonia, phenolic compounds, extracellular polysaccharides, siderophores, ligands of cations and cation exchange are involved in the biodissolution of K, Zn and Si. Frateuria aurantia, Bacillus mucilaginosus and B. edaphicus and Bacillus sp are recognized as potash mobilizers, silica and zinc solubilizers.

Abstract

Soil is the store house of 1/4^th of the global biodiversity. Arbuscular mycorrhizal (AM) fungi is one of the important group of organism occurring in soil. The beneficial effect of AM fungi in improving plant growth is well documented. Many of the functions performed by AM fungi can provide essential services to human society. These services include nutrient cycling, soil structure, plant growth promotion, resistance against biotic and abiotic stresses and bioregulation of plant development. These services are not only essential to ecosystem function but also a critical resource for the sustainable management of agricultural systems. Recent studies have brought out that both plant biodiversity and ecosystem productivity increases with the increasing number of AM fungi. Thus, it appears that the diversity of AM fungi in soil is a major factor contributing to the maintenance of plant biodiversity and the ecosystem functioning. The role of AM fungi in ecosystem services, plant diversity and land productivity are discussed in this review.

Abstract

Agricultural production is often limited by low phosphorus (P) availability. In developing countries, which have limited access to P fertiliser, there is a need to develop plants that are more efficient at low soil P. Arbuscular mycorrhizal (AM) symbioses are widespread in the plant kingdom and contribute significantly to plant P nutrition and growth in natural ecosystems. Production and application of these beneficial fungi for agricultural purposes has grown over the last decades worldwide. However, the necessity of AM inoculum production via a host plant is still an obstacle to ample utilization of AM fungi in agricultural crops. The present article deals with the basic and applied aspects of AM research and its role in sustainable agriculture.

Abstract

Cyanobacteria comprise a group of photosynthetic prokaryotes, which exhibit versatility in their morphological, biochemical and molecular characteristics and represent an untapped source of novel metabolites and genes. Their structural-functional flexibility makes them successful in diverse and extreme environments including high temperatures or levels of UV light and salinity, and co-exist in symbiotic/parasitic/mutualistic associations with various members of Plant and Animal kingdom. The intracellular colonization of cyanobacteria in wheat and rice roots and their potential as plant growth promoting agents for several crops, besides rice, has led to the deployment of novel formulations of cyanobacteria and agriculturally useful bacteria as biofilms and disease suppressive options in field studies.

Abstract

The nutrition of tobacco plants relies upon the plant genotypic variation and soil characteristics which also influence the various microflora that inhabit the rhizosphere. The investigations were aimed to analyze the role of native and inoculated plant growth promoting bacteria on the uptake of major plant nutrients viz., nitrogen, phosphorus and potassium and also their supportive nature in reducing the infection caused by  Pythium aphanidermatum, the damping-off fungus of tobacco in nursery. Rhizosphere microorganisms include PGPR viz., Azotobacter, Azospirillum, Pseudomonas and Bacillus, AM fungi and Streptomyces. The addition of these microbes as bioinoculants in tobacco integrated nutrient and disease management resulted in better quality tobacco worth premium price.

Abstract
 
This work aimed to evaluate agromicrobes preponderance and activity in maize ecosystem of same soil types (diara land/fragile land) under different agricultural practices. We conducted a five year field survey of grower’s field to investigate the effect of tillage system, maize plant genotypes and soil organic carbon level on preponderance of diazotroph (Azotobacter), plant growth promoting rhizobacteria (Pseudomonas) and arbuscular mycorrhiza (AM) colonization of maize ecosystem. No tillage, traditional maize cultivar and soil organic carbon (>1%) appear to support the preponderance of targeted diazotrophs, plant growth promoting rhizobacteria (PGPR) in maize rhizosphere and AM colonization of maize root. Elevation in the preponderance of bacteria, Azospirillum population in maize root, AM colonization, microbial biomass, nitrogen mineralization, phosphate solubilising microbes, cellulose hydrolyzing microbes and acetylene reducing assay (ARA)  of maize root appeared due to organic fertilization of maize crop.

Abstract

Of the various rhizosphere associated bacteria, Azospirillum species are probably the most studied and appear to have significant potential for commercial application. During the last 35 years of studies of Azospirillum–plant interaction, over 20 proposals were suggested for the mechanism of action by which Azospirillum  enhances plant growth, yield and nutrient uptake. Besides, fixing the nitrogen with associative symbiosis, they impart a number of beneficial effects on plants such as phytohormone production, siderophore production, enzyme production, proliferation of root system, enhanced water and mineral uptake, mobilization of minerals, mitigation of environmental stressors of plants, and moderate biocontrol potential. The following plant responses to Azospirillum inoculation in agriculture crops were often reported: increase the germination percentage and height of the seedlings, increase the total number and length of adventitious roots and root hairs, increase the hydraulic conductivity of the root system, increase in the height of the shoot and dry matter production and yield of the crop plants. The effect of Azospirillum inoculation on the total yield increases of field grown plants generally ranged from 10 to 30 per cent. This article reviews the recent researches on role of Azospirillum in plant growth promotion.

Abstract

Microorganisms execute many key functions that regulate the processes related to the fertility status, nutrient transformation, nutrient conservation, and soil health management that are crucial for agronomic sustainability. Rice soils offer peculiar conditions for microorganisms that support diametrically opposite biochemical reactions under flooded conditions. It is pertinent to note that both reduction and oxidation reactions of several essential nutrients mediated by microbes occur simultaneously in the flooded soils at various depths, profiles and stages of rice crop growth in concurrence. This is peculiar and specific to rice soils as the cultivation process demands changes in water regimes, operative and management practices.

Abstract

Current trend of global agricultural systems entails preference towards sustainable crop production through organic agriculture (ecology based) as compared to conventional (synthetic input based). In order to claim as organic, it needs to be certified as per requirements organic standard. The soil fertility management organic standard requirements of major countries are outlined. This review article compares the agricultural management practices of organic and conventional systems so as to assess its impacts on microbial biodiversity, microbial activities on soil functioning and long term fertility based on long term field studies conducted in different parts of the globe.

Abstract

Any environmental variable, can adversely affect the optimal growth conditions of the plants. The stressed environment makes the plants to alter their physiology for survival rather than reproduction. Prolonged drought, intense raining, frequent floods, cold waves high and low temperatures are the predicted abiotic stresses in the future due to climate changes. Water stress is one of the important growth limiting factor which decreases plant growth during vegetative stage. Crops grown under rain-fed conditions are the most affected by seasonal variations in rainfall. Therefore failure of monsoon, high temperature and salinity usually result in water stress. In addition, it causes serious negative impacts on crop growth and yields. A greater stress tolerance capacity could also be largely attributed to the plants by the symbiotically associating microorganisms capable of modulating stress factors. The microorganisms having close association with plants are referred as plant associated bacteria (PAB), which can be grouped into rhizospheric (in vicinity of root) and rhizoplanic (on surface of root), endophytic (inside the plant tissue)  and phyllospheric (on the leaf surface ) bacteria. Among the PAB, pink pigmented facultative methylotrophic (PPFM) bacteria belonging to the  genus Methylobacterium are well known for their intimate ubiquitous occurrence in the plant.

Abstract

The medicinal plant, Nithyakalyani, Catharanthusroseus is valued for its alkaloid and the content varied, among root (0.14 to 1.43%), stem (0.48%), fruit (0.4%), seed (0.18%) and pericaup (1.14%). The biofertilizer consortium development includes Catharanthusroseus. Azosppirillumlipoferum CAZS-4, Azotobaterchroococcum CAZB-1, Bacillusmegaterium CPB-18 and Pseudomonasflourescens CPF-14. The relative chemotactic response (RCR) of the strains to anionic fraction is more than that of cationic and neutral fractions. The consortium treated plants possessed 1.120 mg g^-1 of ajmalicine on 180 DAS, and the antioxidant superoxide dismutase (SOD) (13.240 U mg of protein hr-1), peroxide (POX) (11.240 U mg of protein hr-1) and catalase (CAT) (9.000 U mg of protein hr^-1) values were higher on 150 DAS. The consortium increased the biomass production by 50-75 per cent with proportionate increase in the mineral nutrient content. Biofertilizer consortium is the most effective organic input for biomass production.

Abstract

Plant-associated microorganisms play a significant role in conferring resistance to abiotic stresses. These organisms include rhizoplane and endophytic bacteria and symbiotic fungi and operate through a variety of mechanisms like triggering osmotic response and induction of novel genes in plants. The development of stress tolerant crop varieties through genetic engineering and plant breeding is essential but a long and strained process, whereas microbial inoculation to alleviate stresses in plants could be a more cost effective environmental friendly option which could be available in a shorter time frame. Considering the current trends available, intensive future research is needed in this area, particularly on field evaluation and application of potential organisms.

Abstract

The pressure due to increase in world population necessitates an increase in agricultural production and this warrants the vital importance of research in plant and soil productivity. Applications of chemical fertilizers and pesticides have resulted in soil pollution, desertification and salinisation which disrupted the agriculture production. A suitable microbial technology to improve the soil health and plant productivity has been invented. Increase in the use of bacterial fertilizers substantially reduced the use of chemical fertilizers. Similarly invention of specific antagonistic microbes which control pathogen and stimulate plant growth resulted in lesser use of agrochemicals. Selection, development and application of such microbial strains to the agronomic crops resulted improving the fertility of such affected soil. The studies on plant growth promoting rhizobacteria (PGPR) on the growth and nutrient uptake of various plants have been well studied. Presently, it has been found that the use of beneficial microbes can enhance the resistance ability to adverse stresses. Some mechanisms by which the beneficial microorganisms are able to stimulate plant growth and arrest plant pathogens include mobilization of nutrients, production of phytohormones, siderophores, organic acids, nitrogen fixation, lowering of ethylene levels in plants and antagonism. Here the recent developments that have been taken place on the interaction between plants and PGPR and their mechanism of action resulting in enhanced agriculture production and soil fertility are discussed.

Abstract

Endophytes are microorganisms  that live inside the living plant tissues for at least part of their life without causing any apparent disease symptoms in the host. In general  they  can be divided into two main types namely, obligate and facultative endophytes. Facultative endophytes are capable to survive in the soil, on the plant surface, inside the plants as well as on artificial nutrients and can be cultured away from their host. Endophytes which inhabit inside plant tissues throughout their lifespan are called as obligate endophytes. Natural products produced by endophytic microbes are found to be antimicrobial, antiviral, anticancer, antioxidants, antidiabetic and immunosuppressant. Therefore, endophytes form an untapped source of novel natural compounds for application in agriculture, medicine and industry.