Preface   There is no limit in thirst of our knowledge and eagerness and this has led to our concurrence that plant kingdom has always been the integral part of all forms of vitality. To understand the myth of life style of plants, its different types of activities have to be deciphered and this is what we call Plant Physiology. However, physiology deals with all the vital activities of a plant and also explains how it reacts to sustain in natural distress. Inside the plant, what types of physiological actions are going on in chemical level, means what compounds are formed and how these react becomes Biochemistry. It explains how a plant can trap the unlimited solar energy in form of chemical bonding and again at different platforms it utilizes this energy to perform different physiological works. This is the energy cycle, the genesis of whole vital world. But thirst of knowledge does not quench here, and man probed still inside up to molecular and genetic levels of these chemical reactions to understand the nature of biochemical reactions and to control if possible up to the desired level and that is Molecular Biology. We have tried to comprise these three aspects of plant system, i.e., Plant Physiology, Biochemistry and Molecular Biology under one canopy in the form of this book, entitled “Developments in Physiology, Biochemistry & Molecular Biology of Plants” contributed with very valuable and relevant chapters by various experts of national and international repute. We trust that the collective wisdom with foresighted vision and dedicated efforts of contributors will fulfil the noble mission of this book in the post genomic era of cyber age. Nevertheless, this book will not only be extremely helpful to satisfy the keenness and inquisitiveness of the students and educators but also enlighten the pavement for researchers of plant science. Distinguished plant scientists, actively engaged in teaching and research at prominent Universities and ICAR Research Institutes have contributed ten pragmatic review articles, which have been subdivided into six major sections. The Chapter 1 of Section I well deals in part with the recent advances made in plant iron nutrition research meticulously reviewing Fe-uptake and distribution in relation to hormones under Fe deficiency stress followed by physiology and biochemistry of iron nutrition and interactions involving iron on crop yield. The Section II of Plant Metabolism consists of three applicable chapters two, three and four. The Chapter 2 embodies regulation of phospholipid metabolism. The control of phospholipid metabolism in plants is an open area of research, as it is needed in perspective of hormonal effects and environmental stresses. Similarly in Chapter 3, the co-author has well emphasized the metabolism of sucrose and starch and their significance. 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. Subsequently in Chapter 4, experienced co-authors has precisely accentuated the knowledge of nitrate assimilation and nitrate reductase activity in plants, as the understanding of physiology and biochemistry of nitrogen nutrition at molecular level is obligatory and likely to add insight to achieve the hard task goal.

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.

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 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.

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 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 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 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 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 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.

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.

Index a-amylase, 43,44,46     a-glucosidase, 43,45, 46     b-amylase, 43,44,47     b-D-fructofuranoside fructohydrolase, 37     b-ketoacyl ACP reduetase, 25        -synthetase, 25     d aminolevulinie acid, 131     1-aminocyclopropane-1-carboxylic acid, 9     1,5-biphosphate carboxylase activity, 187     2-(4-carboxyphenyl)-4,4,5,5-tetramethylimi-dazoline-1-oxyl-3-oxide, 10 2, 4-D, 205,207,222,272