GROWTH AND DEVELOPMENT : GROWTH AND DEVELOPMENT ‘Growth’ - definition: Growth and Development are the most fundamental and conspicuouscharacteristics of all living organisms. According to dictionary, G rowth is an advancement towards maturity. And Development is a gradual increase in size. The plant physiological definition of G rowth is ‘an irreversible increase in mass, weight or volume of a living organism, organ or cell. Growth Curve : : Growth Curve : This canbe divided into three phases. 1 . Lag period of growth: During this period the growth rate is quite slow because it is the initial stage of growth. 2 . Log period of Growth During this period, the growth rate is maximum and reaches the top because at this stage the cell division and physiological processes are quite fast. 3. “ Senescence period or steady state period : During this period the growth is almost complete and become static. Thus the growth rate becomes zero. A TYPICAL ‘S’ SHAPED GROWTH CURVE : A TYPICAL ‘S’ SHAPED GROWTH CURVE Growth pattern of annual crops: : Growth pattern of annual crops : LAG PHASE LOG PHASE STATIONARY PHASE AND DEATH . TYPES OF GROWTH: TYPES OF GROWTH : a) Determinate Organs : Those organs that grow to certain size and then stop growing are called determinate organs. After their growth is completed they eventually senesce and die. Examples of such organs are leaves, flowers and fruits etc. Determinate Growth: If , reproductive growth starts only after completion of vegetative growth it is called as determinate growth habit. Eg . Maize. PowerPoint Presentation: Indeterminate Organs : Those organs which grow continuously with the activity of meristems are indeterminate organs. Ex. Are roots and vegetative stems of perennials. These structures always remain youthful, because of the meristematic activity. Indeterminate Growth: Here , vegetative and reproductive growth overlaps. This is shown in plants that have a capacity for both vegetative growth and flowering over an extended period. Eg . Red gram , Soybean etc., Monocarpic and polycarpic species : : Monocarpic and polycarpic species : Monocorpic species flower only once and then die. Thus, in a sense mononcarpic species are determinate as for as the entire plant is concerned. Most monocrapic species are annuals Many varieties of bamboos may grow and live for over 50 years Thus bamboos are perennial but monocarpic Ex.Rice , Maize,Sunflower,Sugarcane,sorghum etc. Polycarpic species flower more than once in life cycle. Here, the vegetative and reproductive periods overlap each other. This is seen in most of the tree species. .. All polycarpic plants are perennials. Development: Development Growth leads to the Development . Development is defined as ordered change or progress often towards a higher, more ordered or more complex state . However , these two processes are often linked together and occur in sequence. Growth is a quantitative change in contrast to Development which is more of a qualitative change. INITIATION AND DEVELOPMENT OF VEGETATIVE STRUCTURES: : INITIATION AND DEVELOPMENT OF VEGETATIVE STRUCTURES: Root growth: Radicle is the embryonic root. During the seed germination and seedling formation, it grows to form primary root of the seedlings. A growing root usually has 4 distinct regions , 1. Root cap 2. Meristematic region 3. The region of cell elongation and 4. The region of differentiation and maturation PowerPoint Presentation: F.A.L. Clowes and B.E. Jupiner (1968) demonstrated that there is a quiescent centere in the meristematic region, where no cell division takes place. This centere is located just above the root tip. It is surrounded by a group of actively dividing cells, which give rise to the column of cells forming roots. The region of cell elongation is made up of column of newly derived cells. It is the elongation of these cells, which causes the root tip to project forward and push through. Most cells in this region elongate at least 15 folds and increase in diameter which results in the development of considerable pressure by the elongation of root. The region of differentiation and maturation: The region of differentiation and maturation The cells in the region of differentiation and maturation differentiate into various tissues, characteristic to the mature root; the epidermis, cortex and stele. In roots xylem and phloem differentiate only acropetally and as continuation of the older xylem and phloem in the more basal part of the root. During differentiation most cells increase in size and vacuolation PowerPoint Presentation: Stem growth : The life of stem starts as a plumule. It grows to form theshoot of the seedling. The longitudinal growth of stem and formation of various organs like branches, leaves, flowers is the function of stem meristem. Tunica Corpus Theory: Tunica Corpus Theory: : Tunica Corpus Theory: To explain the cellular organizations of stem meristem, A.Schmidt (1924) first proposed a tunica corpus theory . Accordingly , most apical meristems contain two zones, an outer tunica and an inner Corpus. Tunica consists of one to several layers of cells at the surface of the merisem while corpus cells are beneath the tunica layer. The cells in tunica divide by anticlinal division i.e in a plane perpendicular to the surface of the stem, whereas, the corpus cells divide in many different ways.The formation of branches leaves or outer appendages on the stem are initiated. in the formation of a primordium or out growth at the surface of the meristem, just below the tip. In the formation of aerial organs both tunica as well as corpus layers are involved. The tunica normally forms the epidermis of the organ derived from the meristem, while corpus cells produce majority of the internal tissues of the new organ. Auxin s normally promote the elongation of stem. They induce the elongation of cells. Gibberellins also promote stem elongation and they do this by promoting cell division as well as cell elongation. Leaf initiation and Growth: Leaf initiation and Growth Elevations appear on the periphery of themeristem in a regular pattern. Leaf primordia appear as dome shaped on theperiphery of the stem. They appear at nodal positions of the stem, which have an intercalary meristem when the leaves are to be produced in pairs; each pair usually appears to right angle to the preceding pair, the two leaves in a pair generally opposite to each other. The growth of individual leaf also follows the typical sigmoidal pattern, just like the growth of the entire plant. In most plants, the shape and form of leaves are fixed and little variation found among them. However, many plants have leaves of different shape. The phenomenon is termed as heterophylly, which is quite common in aquatic plants. INITATION AND DEVELOPMENT OF REPRODUCTIVE STRSCTURES : INITATION AND DEVELOPMENT OF REPRODUCTIVE STRSCTURES Initiation and Development of Flower: Once the biochemical requirements for evocation of flowering are completed and the meristem has reached the point of no return, it develops either into an inflorescence (a cluster of flowers) or solitary flowers. In most plants, the pattern of flower initiation and development is almost similar. . Some protuberances develop from this meristem in a whorled manner. Floral parts (sepals,petals etc) are formed due to the development of the protuberances. The outer most whorl of the protuberances forms the sepal and next to it forms petals and so on. Most plants produce bisexual flowers containing functional male (stamens) and female (pistils) parts. opening is usually due to the differential growth of the inner and outer sides of the sepals and petals. Initiation and Development of Flower: Initiation and Development of Flower Once the biochemical requirements for evocation of flowering are completed and the meristem has reached the point of no return, it develops either into an inflorescence (a cluster of flowers) or solitary flowers. In most plants, the pattern of flower initiation and development is almost similar. The apex almost becomes flat from conical,due to the inhibition of growth in the central portion of the meristem. Some protuberances develop from this meristem in a whorled manner. Floral parts (sepals, petals etc) are formed due to the development of the protuberances. The outermost whorl of the protuberances forms the sepal and next to it forms petals and so on. Most plants produce bisexual flowers containing functional male (stamens) and female (pistils) parts. Other species contain staminate (male) and pistillate (female) flowers only on different individual plants. Auxins and Ethylene stimulates the formation of female flowers, where as gibberellins increase the ratio of male to female flowers in the cucumber. Initially, the floral parts are tightly enclosed with in the outer most part, the sepals, constituting a floral bud. Subsequently expansion of the flower bud in to an open flower occurs. The cause of the flower opening is usually due to the differential growth of the inner and outer sides of the sepals and petals. Fruit and Seed Development: : Fruit and Seed Development: The first stage in fruit and seed development is rapid cell division without much enlargement due to cytokinin production by the endosperm which is growing at this stage. Various tissues of the parent plant viz , the ovary, receptacle and sometimes parts of the floral tube may be involved in the formation of fruits. Following the cell division stage cell enlargement phase of growth proceeds and this is by auxins produced in the seeds. If the seeds are removed from a developing fruit, development stops, however it can be restarted again by the application of auxins . At this stage in the development of fruits the concentration of organic acids and sugars begin to increase followed by decrease in osmotic potential. This is related to the increasing absorption of water and growth by enlargement of cells. MEASUREMENT OF GROWTH: MEASUREMENT OF GROWTH Growth can be measured by a variety of parameters as follows A. Fresh Weight B. Dry Weight C . Length D. Area GROWTH ANALYSIS: : GROWTH ANALYSIS : Growth analysis is a mathematical expression of environmental effects on growth and development of crop plants. This is a useful tool in studying the complex interactions between the plant growth and the environment. Growth analysis in crop plants was first studied by British Scientists (Blackman 1919, Briggs, Kidd and west 1920, William 1964, Watson 1952 and Blackman, (1968). This analysis depends mainly on primary values (Dry weights) and they can be easily obtained without great demand on modern laboratory equipment. PowerPoint Presentation: According to the purpose of the data, leaf area and dry weights of component plant parts have to be collected at weekly, fortnightly or monthly intervals. This data are to be used to calculate various indices and characteristics that describe the growth of plants and of their parts grown in different environments and the relationship between assimilatory apparatus and dry matter production. These indices and characteristics are together called as growth parameters Advantages of growth analysis : Advantages of growth analysis a) We can study the growth of the population or plant community in a precise way with the availability of raw data on different growth parameters. b) These studies involve an assessment of the primary production of vegetation in the field i.e. at the ecosystem level (at crop level) of organization. c) The primary production plays an important role in the energetics of the whole ecosystem. d) The studies also provide precise information on the nature of the plant and environment interaction in a particular habitat. e) It provides accurate measurements of whole plant growth performance in an integrated manner at different intervals of time. Drawbacks of Growth Analysis: Drawbacks of Growth Analysis In classical growth analysis sampling for primary values consist of harvesting (destructively) representative sets of plants or plots and it is impossible to follow the same plants or plots through out whole experiment PowerPoint Presentation: Growth Characteristics – Definition and Mathematical Formulae The following data are required to calculate different growth parameters in order to express the instantaneous values and mean values over a time interval. In the following discussion W, W L, WS and WR are used to represent the dry weights of total plant(w), dry leaves(wL), stem(W S) and roots(WR) respectively. Whereas A is the leaf area and P is the land ar ea . PowerPoint Presentation: Crop Growth Rate (CGR):C W2 – W 1 1 CGR = -------- X ----- (g m -2 day -1 ) T2 – T1 P PowerPoint Presentation: Relative Growth Rate (RGR):R The term RGR was coined by Blackman. It is defined as the rate of increase in dry matter per unit of dry matter already present.This is also referred as Efficiency index since the rate of growth is expressed as the rate of interest on the capital. It provides a valuable overall index of plant growth. The mean relative growth rate over a time interval is given below. Loge W 2 – Loge W 1 RGR =---------------------- (g g-1 day -1) T2 – T1 PowerPoint Presentation: Net Assimilation Rate (NAR):E: The NAR is a measure of the amount of photosynthetic product going into plant material i.e. it is the estimate of net photosynthetic carbon assimilated by photosynthesis minus the carbon lost by respiration. The NAR can be determined by measuring plant dry weight and leaf area periodically during growth and is commonly reported as grams of dry weight increase per square centimeter of leaf surface per week. This is also called as Unit leaf rate because the assimilatory area includes only the active leaf area in measuring the rate of dry matter production. The mean NAR over a time interval from T1 to T2 is given by W2-W1 Log e A2 – Log e A1 NAR = ------------------X-------------------------------------- g cm-2 wk-1) T2-T1 A2 – A1 PowerPoint Presentation: Leaf Area Ratio (LAR) The LAR is a measure of the proportion of the plant which is engaged in photosynthetic process. It gives the relative size of the assimilatory apparatus. It is also called as capacity factor. It is defined as the ratio between leaf area in square centimeters and total plant dry weight. It represents leafiness character of crop plants on area basis. A LAR = ------- (cm2g-1) W PowerPoint Presentation: Leaf Weight Ratio (LWR) It is one of the components of LAR and is defined as the ratio between grams of dry matter in leaves and total dry matter in plants (g). Since the numerator and denominator are on dry weight basis LWR is dimensionless. It is the index of leafiness of the plant on weight basis. WL LWR = ------- W PowerPoint Presentation: Specific Leaf Area (SLA) It is another component of LAR and defined as the ratio between leaf area in cm2 and total leaf dry weight in grams. This is used as a measure of leaf density. The mean SLA can be calculated as A SLA = -------- (cm2g-1) WL PowerPoint Presentation: Specific Leaf Weight (SLW) The reversal of SLA is called as SLW. It is defined as the ratio between total leaf dry weight n gms and leaf area in cm2. It indicates the relative thickness of the leaf of different genotypes. WL SLW = ------- (g cm-2) A PowerPoint Presentation: Leaf area index (LAI): D.J. Watson coined this term. It is defined as the functional leaf area over unit land area. It represents the leafiness in relation to land area. At an instant time (T) the LAI can be calculated as LAI = A/P unit less For maximum production of dry matter of most crops, LAI of 4-6 is usually necessary. PowerPoint Presentation: LAD (LAI basis) += LA1 + LA2 (T2 – T1) ----------------- 2 This is expressed as cm2 d -1 PowerPoint Presentation: Leaf Area Duration It is usually expressed as a measure of leaf area intigrated over atime period. Some takes into account both the magnitude of leaf area and its persistence in time. It represents the leafiness of the crop growing period Unit of LAD is Days ,week or months.