Preface Plant physiology is one of the most important disciplines of biological sciences. In recent times, it has gained significant attention from scientists and students working in different area of life science. It is a science that links fundamentals and applications, there by invites many people including academicians, researchers to read and understand the various aspects of Crop physiology. Although, many textbooks available for plant physiology, difficulty in understanding the terminologies in Crop physiology become a hindrance to fully utilizing the textbooks of Crop physiology. To full fill the needs of the students and scientists working in the area of plant science, efforts were made to write this book which has come up in this form. This book has most of the terminology which is commonly used mainly in Crop physiology and also from biochemistry, plant breeding & genetics, agronomy, soil science. Besides, few statistical terms that are commonly used in biological research also included. This book will be of immense use to the undergraduates and postgraduates’ students of agriculture, biochemistry, and botany and would also helpful in various competitive exams including UPSC, TNPSC, Agricultural officers, Horticultural officers and other exams.

Abiotic stress: Unfavourable situation created by non-living factors to the growth and development of plants. Factors include water, temperature, soluble salts, heavy metals, etc. Abscissic acid (ABA): A plant hormone belongs to isoprenoid compounds. It is also known as stress hormone since it has relevance in stress tolerance in plants. Some of the physiological effects of ABA are closing of stomata, synthesis of osmolytes and seed dormancy. Abscission layer: Distinct layer of cells with weakened cell walls in abscission zone. Abscission zone: A region near the base of petiole of leaf which contain abscission layer.

Bacteriochlorophylls: A group of light absorbing photosynthetic green pigments of anoxygenic photosynthetic bacteria. Ballistic transformation: The use of a particle gun to insert foreign DNA into a host. Beneficial elements: These are the elements that help to optimize the growth and development only in some species. It is not essential to all the plants. Aluminum is beneficial to some species that are adapted to acidic soils. Cobalt can have a number of beneficial effects, especially in leguminous plants. Betalains: Highly coloured nitrogen containing glycosylated compound in the category of alkaloids imparting red-purple and yellow colour in plants of centropsermae (e.g., beet root). Beta-oxidation: Breakdown of fatty acids into Acetyl co-A by successive oxidation. It is the first step of lipids breakdown. Bidirectional transport: Simultaneous transport of solutes in opposite directions in the same file of sieve elements. Bidirectional transport may occur under some circumstances. For e.g., in a file of cell, as a result of cytoplasmic streaming.

C3 cycle or Calvin cycle: It is a process of dark reaction of photosynthesis. It is also called as photosynthetic carbon reduction cycle which results in the production of sugars. It occurs not only in C3 plants but also in C4 and CAM pathway also. It occurs in the mesophyll cells. It is described in three stages: (1) Carboxylation, (2) Reduction, (3) Regeneration. C3 plants: Group of plants with calvin cycle wherein the first stable product is 3-phosphoglyceric acid, a three carbon compound. e.g., rice, wheat, barley. C4 cycle: C4 cycle may also referred to as the dicarboxylic acid cycle or Hatch and Slack Cycle. The first stable product is a C4 compounds like oxaloacetic acid. Here CO2 molecule is accepted by phosphoenol pyruvate in the carboxylation reaction. The main purpose of this cycle is carbondioxide enrichment. C4 plants: Plants with Hatch-slack pathway and kranz anatomy of leaves in which the first stable product is four carbon compound, oxaloacetic acid. These plants posses high photosynthetic efficiency and low photorespiration rate. e.g., sugarcane, maize, sorghum.

Dark reactions: It is light independent reactions occurs during daytime. This includes C3, C4 and CAM pathway involving the utilization of NADPH and ATP to fix CO2 into carbohydrates. It is also called as stromal reactions. Day neutral plants: The plants that flowers regardless of the length of the period of the light that is exposed to. They are called as day neutral plants. DCMU (Dichlorophenyl dimethyl urea or diuron): An herbicide that inhibits non-cyclic photophosophorylation specifically blocks the electron flow at the quinone acceptors of PSII, by competing for the binding site of plastoquinone that is normally occupied by PQB. DCPIP (Dichlorophenol indophenols): A dye often used as artificial hydrogen acceptor to demonstrate in Hills reaction in isolated chloroplast in laboratory. The oxidized form is blue in alkali and red in acid, while reduced form is colourless.

Ectodormancy: A kind of dormancy which is due to environmental factors. EDTA: An important chelating agent often used in modern nutrient solutions. It forms soluble complexes with metal ions such as that of iron and prevents from precipitation in the solution. Elaiosomes: Greek élaion means “oil” and sóma means “body” , are fleshy structures that are attached to the seeds of many plant species. The elaiosome is rich in lipids and proteins, and may be variously shaped. Many plants have elaiosomes that attract ants, which take the seed to their nest and feed the elaiosome to their larvae and by which the seed get dispersed. Electrical conductivity: Electrical conductivity is the measure of a material’s ability to allow the transport of an electric charge. It is used to measure the level of salinity in water or soil. When electrical conductivity is more, then salinity is more since as salt concentration is more in water or soil, then those salts will conduct more of electricity. Normally measured in μS/cm. Electrical impedance: The application of alternating electrical current to pre-frozen or frozen plant tissues to predict damage or measure injury, respectively.

Gel: A semi-solid medium in to which proteins or nucleic acids are subjected to electrophoresis, to determine their size or to separate them from other components. Gene family: A set of genes whose sequences differ only slightly that encode identical products; within a single species, a multigene family. Gene tagging: The addition of a marker to a gene; often by the introduction of a transposon or insertion element. Gene transfer: Transformation; the insertion of foreign DNA into a host conferring a trait not previously inherant in that organism. Gene: The concise meaning might be the sequence of DNA that encodes a gene product (an RNA or protein), including all upstream and downstream sequences involved in the expression of the gene. Genome: Sum of all genetic information of an organism, nucleus, organelle, or virus. Geotropism (Barytropism or gravitropism): When a seedling is kept horizontally on the soil, the radicle always grows towards soil, and the plumule grows away from the soil. This type of growth movement of radicle and plumule is called positively geotropic and negatively geotropic respectively. But some runners and rhizomes grow parallel to the surface of the soil and this is referred to as diagiotropic. When the lateral roots grow obliquely into the soil, it is referred to as plagiogeotropic phenomenon. Germination percentage: Germination percentage is an estimate of the viability of a population of seeds.

Facilitated diffusion: Facilitated diffusion is a movement in the direction of a concentration gradient; but it involves moving through a channel protein or a carrier protein. A channel protein is merely a pore in the membrane, and is often gated to control movement. A carrier protein has a binding site where the substance attaches and moved through the membrane. Facultative CAM: Plants which behave as C3 under conditions of normal water supply. However, switch over to CAM mode under conditions of water deficit. FAD (Flavin adenine dinucleotide): A riboflavin containing co-enzyme of some oxidation reduction reactions. Facultative long day plant: Facultative photoperiodic plants are more likely to flower under appropriate light conditions, but will eventually flower regardless of length of night. FADH: In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism. FAD can exist in three different redox states, which are quinone, semiquinone and hydroquinone. FAD is converted between these states by accepting or donating electrons. FAD, in its full oxidised form or quinone form, accepts two electrons and two protons to become FADH2 (hydroquinone form). The semiquinone (FADH) can be formed by either reduction of FAD or oxidation of FADH2 by accepting or donating one electron and one proton, respectively.

Ice nucleation: It is a process of reducing the formation of ice crystal under freezing stress, by some polysaccharides and proteins known as ice nucleators. Imbibitions: It is a special type of diffusion when water is absorbed by solids-colloids-causing them to enormously increase in volume. The classical examples of imbibition are absorption of water by seeds and dry wood. Immobile elements: The elements which get translocated slower inside the plant are called immobile elements. Examples: Ca, Fe and B. Immunoassay: This is very sensitive method of identifying and or quantifying the hormones and other molecules which has antigen and antibody interaction. Indeterminate growth: Plant growth in which the main stem continues to elongate indefinitely without being limited by a terminal inflorescence or other reproductive structure; also growth is characterized by sequential flowering from the lateral or basal buds to the central or uppermost buds. Indole -3 acetic acid: It is naturally occurring auxin responsible for cell elongation, apical dominance and other physiological functions of auxins. Induced dormancy: Induced dormancy in which dormancy develops as a response to external environmental factors.

Jasmonic acid: Jasmonic acid is derived from the fatty acid, linolenic acid. It is a member of the jasmonate class of plant hormones. It is biosynthesized from linolenic acid by the octadecanoid pathway. The major function of JA and its various metabolites is regulating plant responses to abiotic and biotic stresses as a well as plant growth and development processes.

Ketose: A simple sugar in which carbonyl group is a ketone. Kinases: Enzymes that catalyse phosphorylation of an acceptor molecule such as protein molecule by ATP.

Lactate dehydrogenase: An enzyme that reversibly catalyses conversion of pyruvate to lactate by utilizing NAD as coenzyme. This operates under anaerobic respiratory condition. Lactate fermentation: Lactic acid fermentation is a biological process by which glucose and six carbon sugars (also, disaccharides of six carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate. It is an anaerobic fermentation reaction. Latent heat: The heat required to convert a solid into a liquid or vapour, or a liquid into a vapour, without change of temperature. It is also called as hidden heat. Leaching requirement: (LR) The amount of water in excess of the plant requirement that is needed to remove salt from the root zone in order to prevent soil salinity from exceeding a specified value. Leaf Area Duration (LAD): It is the functional leaf area or estimated photosynthetic area which contributed for the total biomasss. To correlate dry matter yield with Leaf area, Power et al., (1967) integrated the Leaf area with time and called as Leaf Area Duration. LAD taken into account, both the duration and extent of photosynthetic tissue of the crop canopy. The LAD is expressed in m2. days.

Macromolecule: A molecule having molecular weight ranging from few thousand to millions. Macronutrients: The essential elements which are required by plants in comparatively large amounts are called as major elements or macro nutrients. Examples: C, H, O, N, P, K, Ca, S, Mg. In this C, H, O, N, P, K are called primary elements and Ca, S, Mg are called as secondary elements. Malate shuttle: A mechanism of transferring reducing equivalent of cytosolic NADH in the form of malate across the inner mitochondrial membrane by a specific ketoglutarate malate transporter for oxidation through electron transport chain in little animal tissue like heart muscle. Malic enzyme: An enzyme that catalyzes the oxidation of malate to pyruvate and carbondioxide.

NAD/NADP (Nicotinamide Adenine Dinucleotide/ Nicotinamide Adenine Dinucleotide Phosphate): Coenzymes acting as carriers of hydrogen atoms and electrons in some oxidoreductases catalyzed reactions. Their oxidized and reduced states are NAD+ and NADH + H+/NADP+ and NADPH + H+ Nanotechnology: Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the molecular level in scales smaller than 1 micrometre, normally 1 to 100 nanometers, and the fabrication of devices within that size range. Nastic movement: Nastic movements are non-directional responses to stimuli (e.g., temperature, humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor or changes in growth. An example of such a response is opening and closing of flowers. There are several types of nastic movements such as Epinasty, Hyponasty, Photonasty, Nyctinasty, Chemonasty, Hydronasty, Thermonasty, Geonasty/Gravinasty, Thigmonasty, etc.

Obligate photoperiodism: Obligate photoperiod plants absolutely require a long or short day before flowering. If required photoperiod condition is not met they won’t flower. This phenomenon is called obligate photoperiodism. Oleosome (Spherosome or oil body): Cell organelle bounded by a single membrane and contains triglycerides. Oligohalophyte: A plant adapted to habitats of low salinity (0.04 to 0.4 MPa at field capacity; EC 1 to 10 dS/m). Oligomycin: An antibiotic that inhibits oxidative phosphorylation by blocking the activity of F0F1 ATP synthase. Oligosaccharide: A molecule containing fewer number of monosaccharide units joined by glycosidic bonds.

P680: Reaction center chlorophyll in Photosystem II (PSII) which absorbs maximum light of 680 nm in its neutral state. P700: Reaction center chlorophyll in Photosystem I (PSI) which absorbs maximum light of 700 nm in its neutral state. P870: Form of bacteriochlorophyll in reaction center of pigment system in photosynthetic purple bacteria that absorbs light maximally at 870 nm in its neutral state. Paclobutrazol: It is a chemical compound which inhibits Gibberellin biosynthesis. It is also a growth retardant commercially used in overcoming alternate bearing of mango. Palindrome: Inverted repeats of DNA such that the sequence is the same when read forward or backward; e.g., CAGTTGAC, or in the English language, “Madam, I’m Adam.” Palisade Parenchyma : Palisade parenchyma cells are seen beneath the upper epidermis. It consists of vertically elongated cylindrical cells in one or more layers. These cells are compactly arranged without intercellular spaces. Palisade parenchyma cells contain more chloroplasts than the spongy parenchyma cells. The function of palisade parenchyma is photosynthesis. Pantothenic acid (Vitamin B5): An important constituent of coenzyme A which is involved in transacylation reactions.

Q10 (Temperature coefficient): The ratio of the rate of chemical reaction at a particular temperature to the rate of that chemical reaction exactly at 10°C lower. Qualitative photoperiod: Qualitative plants are those in which a particular photoperiod is an absolute requirement for the occurrence of a response. Ex: Common cocklebur Qualitative response (absolute response, obligatory response): A plant response, usually flowering, that absolutely depends on some day length, temperature, or other environmental stimulus. If the plant does not experience the required stimulus, the response does not occur (e.g., the plant remains vegetative). Opposite to quantitative response. Quantasomes : Quantasomes are particles found in the thylakoid membrane of chloroplasts in which photosynthesis takes place. They are embedded in a para crystalline array on the surface of thylakoid discs in chloroplasts. They are composed of lipids and proteins that include various photosynthetic pigments and redox carriers.

Radiant energy (Qe, J): The transfer of energy of radiation. Radiation frost: Heat radiated from surface of soil, trees, and any other solid particles to reduce the temperature low enough to cause frost conditions. Solid particles lose heat more rapidly than air, reducing the surface temperature. Eventually the air at low levels becomes cool and heavy compared to air at higher elevations. Occurs more readily on cloudless nights when there is no barrier for retaining the heat (i.e., a barrier that radiates the heat back to earth). Radiation: The emission and propagation of electromagnetic waves or particles through space or matter. Radical (Free Radical): An atom or a group of atoms with an unpaired electron which can exist independently for short period during the course of chemical reaction. Radicle: Embryonic root of seed plants.

Half life: The time required for the disappearance of one half of a given component of a system. Halochromism: It occurs when a substance changes color as the pH changes. This is a property of pH indicators, whose molecular structure changes upon certain changes in the surrounding pH. This change in structure affects a chromophore in the pH indicator molecule. Halomorphic soil : A suborder of the intrazonal soil order, consisting of saline and sodic soils formed under imperfect drainage in arid regions and including the great soil groups Solonchak or Saline soils, Solonetz soils, and Soloth soils. Hatch-Slack pathway: It is one of the carbon fixation pathway used by certain group of plants (C4 plants) where the first stable compound is oxalo acetate, a C4 dicarboxylic acid compound. In the first carboxylation reactions, atmospheric CO2 combines with phosphoenol pyruvate (PEP) to oxalo acetate and then to malate. These plants posses kranz anatomy with mesophyll and bundle sheath cells.

Salicyclic acid: Salicyclic acid (from Latin salix, willow tree, from the substances used to be obtained) is aminohydroxybenzoic acid, a type of phenolic acid and a beta hydracid. It has the formula C7H6O3. This colourless crystalline organic acid is widely used in organic synthesis and function as a plant hormone. It is derived from the metabolic of salicin. In addition to being an important active metabolic of aspirin (acetylsalicyclic acid), which acts in part as a prodrug to salicyclic acid, it is probably best known for its use as a key ingredient in topical anti-acne products. The salts and esters of salicyclic acid are known as salicylates. Salination: The process of accumulation of soluble salts in the soil. Saline adaptation: Genetic modification of individuals in a population that increases their ability to survive excess salt. Saline adjustment: Physiological and biochemical changes of individual plants that increase their ability to survive excess salt.

Tannins: Group of plant phenolic compounds found in higher plants as secondary metabolites. Their main function is to defense against microorganisms, insects, and herbivores and in allelopathy. Taxis (tactic orientation; formerly topotaxis): Movement of motile organisms, cells or organelles, the prevailing direction of which is determined by the direction of the stimulus. TATA box (Hogness box): A sequence of nucleotides which serves as the main recognition site for the attachment of RNA polymerase in the promoter region of eukaryotic genes. Located at around 25 nucleotides upstream of the transcriptional start site. It consists of seven base consensus sequence, TATAAAA. TCA cycle: Tricarboxylic acid cycle. It is also called as citric acid cycle or Krebs cycle, It is a step in aerobic degradation of glucose to convert into energy. During this cycle several intermediates are produced, which leads to several metabolic pathways. During this cycle, there is production of reductancts such as NADH, FADH and GTP. Telomere: Sequences at both termini of each eukaryotic chromosome that facilitate replication.

Ubiquinone (UQ): It is a lipophilic metabolite that functions in the electron transport chain in the plasma membranes of prokaryotes, and the inner mitochondrial membranes of eukaryotes, apart from its roles as an antioxidant and in the regeneration of tocopherols. Also called as Coenzyme Q. Ubiquitin: It is a small protein that is found in almost all cellular tissues in all eukaryotic organisms,( i.e. it occurs ubiquitously) which helps to regulate the processes of other proteins in the body. Ultracentrifuge: A high speed centrifuge with speed upto 60,000 rpm and centrifugal field of 500,000 x g

Vacuole: A fluid filled space within the cytoplasm surrounded by membrane called as tonoplast, that occupies most of the volume of cell. Aside from storage, the main role of the central vacuole is to maintain turgor pressure against the cell wall. Valinomycin: An antibiotic that uncouples electron transport and oxidative phosphorylation only in presence of some cations such as K+ or Na+ Van der Waals interaction: Weak intermolecular forces between molecules as a result of each inducing polarization in the other.

Wall pressure: The inward pressure exerted by the cell wall against expanding protoplast; equal but opposite to turgor pressure. Warburg effect: Warburg effect states that the competition between CO2 and O2 for enzyme RuBisCO with CO2 promoting photosynthesis and inhibiting glycolate formation and inhibiting photorespiration and O2 promoting glycolate formation and inhibiting photosynthesis. Water deficit: Water available to the plant is less than optimum requirement. Water potential (ψw): Water potential is defined as free energy status of water in a system compared to the free energy status of pure water. Here system refers to water in plant cell or soil and pure water refers to the water which does not have any solute in it. Water potential is measured in terms of bars, Pascals or Megapascals and denoted by ψw.

Xanthophylls (Carotenoids): These are tetraterpenes with general formula C40H56O2. Xanthophylls are a class of oxygen-containing carotenoid pigments, responsible for the color of many of the yellow, orange, and red hues of flowers, fruits, vegetables (corn, pepper, etc.), egg yolks, and feathers, shells, or flesh of many animal species (flamingo, canary, shrimp, lobster, chicken, or salmonids). In plants, they are involved in photosynthesis with chlorophyll and are responsible for the red, yellow, and/or brown colors of autumn foliage as the chlorophyll levels decline. Xeromorphy: Morphological characteristics, such as small, tough leaves, a heavy cuticle, etc., that are generally important for adaptation to dry environmental conditions.

Yamogenin: A triterpene plant steroid belonging to a group of sapongenins that is obtained from Dioscorea and is used in making oral contraceptives.

Z scheme: Refer non-cyclic electron transport. Z-DNA: A duplex DNA structure in which helical coiling of the two polynucleotide chains is left handed and phosphate backbone of the polynucleotides follows a zig-zag course. Zeatin: Most abundant natural cytokinin present in plant.