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Improvement in Nitrogen Use Efficiency and Yield of Crop Plants by Sustained Nutrient Supply and Enhanced Nitrogen Assimilation |
Rana P. Singh1, Manoj Kumar1 & Pawan K. Jaiwal2 |
1Department of Environment Sciences, Babasaheb Bhimrao Ambedkar (Central) University, Rae Bareli Road, Lucknow-226 025, U.P. 2Department of Biosciences, M.D. University, Rohtak-124 001. |
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Plants are responsive to the applied Non-scheduled caste, which constitute most of the vita acromolecules 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).
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Physiology and Biochemistry of Disease Resistance in Plants |
A. Bhattacharya1 and Vijaylaxmi1 |
1Division of Physiology, Biochemistry & Microbiology, Indian Institute of Pulses Research, Kanpur-208 024. |
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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). Before examining the different aspects of physiological and biochemical basis of disease resistance in plants it would be better to examine first the effects of different plant diseases on the various physiological as well as biochemical pathways in plants. Growth of multicellular plant is the end result of a series of coordinated physiological processes that depend on the genetic characteristics of the plant, and a myriad of environmental factors. The various physiological and biochemical processes are linked together by regulatory processes which control photosynthesis, respiration, translocation, assimilation etc. Increase in the size of plant is the result of changes in the cell division and expansion. Cell enlargement is followed by differentiation and morphogenetic changes in which specialized organs are formed. Thus, from a developmental point of view, the sequential component processes of growth include cell division, cell enlargement, differentiation, and morphogenesis. To sustain growth and develop-ment and ultimately the reproduction, a plant has to undertake various processes at molecular as well as at organ levels. At molecular levels plants has to capture energy from sunlight and convert it to chemical energy, in conjunction with CO2 from atmosphere and these chemical energy are to be available at the time of need. Plant has to uptake water and various minerals from soil and to utilize them efficiently for growth and development.
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Fungal Stress on Seed Quality |
Jai Prakash Rai1, Asha Sinha2, Alok Kumar Singh1, Deeba Kamil3 and Mohammad Shahid4 |
1Department of Plant Pathology, Faculty of Argiculture, Udai Pratap Autonomous College, Varanasi. 2Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Varanasi-221 005 3Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005., 4Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005. |
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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
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Regulation and Physiological Role of Alternative Oxidase in Higher Plants |
Padmanabh Dwivedi |
Department of Botany, Rajiv Gandhi University, Itanagar-791 111. |
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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). Electron transfer through the cyt pathway is coupled with ATP synthesis, and is inhibited by cyanide, azide and CO2..
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Physiological and Molecular Actions of Salicylate in Plants |
P.K. Singh1, B. Bose2, M. K. Sharma2 and A. Singh |
1Department of Botany, Udai Pratap Autonomous College, Varanasi-221 002, 2Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005. |
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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). It comes in the category of secondary metabolite, which plays an essential role in regulation of plant growth and it interacts with other organisms because it follows the biosynthesis of lignin, the important structural component of the cell wall of plants. Further, it acts as a defense, component of plants against microbes, insects and herbivores. Experimental evidences suggest that salicylic acid functions as signals in plant-microbe interactions, induction of the nod genes of Bradyrhizobium and Rhizobium species occurred by the species-specific flavonoids, a member of phenolic compounds, exudates from legume roots and seeds (Long, 1984). The study of Physical properties suggested that SA can be transported through phloem from the point of initial application or synthesis to distance tissues (Hsu and Kleir, 1990). Modern analytical techniques have confirmed the presence of SA in various plant systems (Mendez and Brown, 1971) and it has been noticed that it is omni present in plant system (Raskin et al., 1990
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Molecular Recognition by Plant Lectins |
J. Datta1 & S. Datta2 |
1Department of Biochemistry, C.S.J.M. University, Kanpur. 2Division of Crop Improvement, Indian Institute of Pulses Research, Kanpur-208 024. |
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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).).
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Strategies for Phytoremediation of Environmental Contamination |
R.D. Tripathi1, S. Srivastava2, Seema Mishra2 & S. Dwivedi2 |
1Ecotoxicology and Bioremediation Group, Environmental Science Division, National Botanical Research Institute, Rana Pratap Marg, Lucknow-226 001 |
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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). A number of metals (Cu, Zn, Fe, Mn etc.) are essentially required by the plant and are important constituent of various biomolecules. However, some other toxic metals (Cd, Pb, Hg, Cr etc.) are non-essential and, when they enter into the plant cell, produce a high level of phytotoxicity. All these elements are toxic as they are immutable by all chemical reactions (Cunningham and Berti, 1996). Both the non-essential toxic metals as well as essential metals at high concentrations cause toxicity as a result of interaction with sulphydryl group of the enzymes (Van Assche and Clijsters, 1990). The adverse effects of heavy metal result in production of reactive oxygen species and generation of free radicals which cause damage biomolecules and disturb cellular functions (Dat et al., 2000) .The primary site of metal interaction is plasmamembrane where metal induces lipid peroxidation and ion leakage. Metals can replace other metals in pigments and enzymes disrupting function of these molecules (Van Assche and Clijsters, 1990). Thus metal toxicity results in intense solute leakage, loss of metabolic activity, chromatid breakdown and even cell death if toxic conditions continue
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Differential Roles of Abscisic Acid in Plants Under Biotic and Abiotic Stresses |
B.K. Sarma |
Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005. |
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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. From an ecological perspective, exposure to one stress may alter the plant’s probability of being exposed to another stress. From a mechanistic perspective, hormonal and biochemical signaling interactions between responses to each stress may influence the severity or ability to adaptively respond to the subsequent stress. Studies in this regards has gained importance tremendously in recent times as the role of ABA in mediating several plant responses to abiotic and biotic stresses has been revealed.
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Drought and Mechanism of Tolerance |
A. Hemantaranjan1, Zaffar Mahdi Dar2 and Sunil Kumar Pandey2 |
1Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005. 2Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005. |
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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). Amongst abiotic stresses, drought is a major limitation to crop productivity worldwide (Boyer, 1982). Drought indices assimilate thousands of bits of data on rainfall, snowpack, stream flow, and other water supply indicators into a comprehensible big picture. A drought index value is typically a single number, far more useful than raw data for decision making. The percent of normal precipitation is one of the simplest measurements of rainfall for a location. Analyses using the percent of normal are very effective when used for a single region or a single season. Normal precipitation for a specific location is considered to be 100%.
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M. Kar1, B.K. Mishra1 and A.K. Sahu1 |
M. Kar1, B.K. Mishra1 and A.K. Sahu1 |
1Department of Plant Physiology, College of Agriculture, Orissa University of Agriculture and Technology, Bhubaneswar-3. |
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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.
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Drought Tolerance in Chickpea (Cicer Arietinum L.) Physiological, Biochemical and Biotechnological Approaches |
Jds Panwar1, Sudhir Kumar2 and Vandana Chaudhary2 |
1Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi-110 012. 2Department of Botany, J.V College, Baraut. |
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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. These adaptive mechanisms include osmotic adjustment, root length density, ion leakage or membrane stabilization, water use efficiency, assimilate mobilization, carbohydrate metabolism, early flowering and pod setting, dehydration tolerance and biological nitrogen fixation. But due to the presence of the above mentioned attributes chickpea has evolved many physiological, morphological, phenological and biochemical characteristics which influences the grain yield and other growth factors of chickpea along with environmental factors.
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Biochemical and Physiological Basis of Salinity Stress Tolerance in Plants |
Malvika Srivastava1 & Animesh Tarafdar1 |
1Department of Botany, D.D.U. Gorakhpur University, Gorakhpur. |
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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.
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