Preface We are ecstatic now to find ourselves in a position to illustrate the decisive theme with the publication of the Volume 2 of the treatise on the Developments in Physiology, Biochemistry and Molecular Biology of Plants. This treatise provides additional information in the crucial areas for making precise and applied research in the national context, on the one hand, and to unravel the science, on the other hand.  In the earlier volume, the theme of publishing this needful treatise has been already made obvious. However, in view of the experiences and enormous advances in plant science research in the last few decades providing enough insight to scan vital research in this century has, almost certainly, enlightened the path to undertake necessary research projects for the benefit of mankind to which we are indispensably committed. The world population has increased from around 1.7 billion to more than 6.0 billion and technological innovations have completely altered our way of living. As a consequence, we are in reality facing considerable environmental variations of a global scale. Farmers, under the circumstances, too have courageously made commendable increase in food production on demand, which could not have been made possible without the untiring endeavours of plant scientists foremost contributions. We, the plant physiologists, biochemists, molecular biologists and plant nutritionists must be proud of our support to the world’s farmers which has helped them make their achievement possible.

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).

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 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 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 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 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 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 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 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 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 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 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.

Index A Aba  141, 148, 205, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 239, 246, 247, 250, 252, 256, 257, 258, 285, 289, 304, 309, 311, 312, 322, 349, 350, 351 Aba accumulation  239, 252, 285, 312 Aba deficient 1  225, 252 Aba insensitive 4 mutants  225, 252 Aba responsive genes  312 Abiotic stress  95, 121, 123, 125, 221, 222, 224, 226, 227, 228, 229, 235, 257, 258, 263, 334, 340, 349, 351, 352, 354 Abiotic stress management  222 Abrin  158 Abscisic acid  153, 154, 221, 222, 225, 230, 231, 232, 233, 234, 235, 249, 252, 259, 265, 297, 355 Abundant (lea) proteins  255, 349 Accumulation  2, 13, 14, 19, 23, 35, 36, 37, 38, 47, 56, 59, 61, 63, 71, 74, 76, 85, 93, 112, 126, 132, 139, 141, 143, 144, 145, 146, 147, 148, 149, 153, 154, 155, 225, 226, 227, 232, 235, 239, 243, 244, 248