Plant Growth and Development

increased growth per unit time(can be expressed mathematically)

arithmetic and geometric

in mitosis only one daughter chell continues to divide and other differentiate and mature (eg:root elongation) ,linear curve is obtained[length of organ against time, equation Lt=Lo+rt (Lt length at time t ,Lo length at time zero, r growth rate or elongation per unit time r is the relative growth and also measure of ability of plant to produce new plant material referred to as efficiency index

after mitosis both progeny cell retain the ability to divide and continue to do so , initial growth is slow (lag phase) and increase rapidly at an exponential rate(log or exponential phase) , with limited nutrient supply the growth slow down (stationary phase), typical for all cells tissues organs of plant eg:tree showing seasonal activities ,sigmoidvor S curvebis obtained [growth parameter against time], expressed as Wt=Woe^rt (Wt finalsize(weight height number ) Wo intial sizeat beginning of period r growth rate t time of growth e base of logrithms

absolute growth rate (measure and comparison of total growth per unit time ) Totalgrowth-initialgrowth 2.relative growth rate growth of given system per unit time expressed on a common basis

H2O,oxygen, nutrients, (temperature,light and gravity affect certain phase or stage of growth)

water :Turgidity of cell helps in extension growth, plant and growth and development is linked water status of plants,water provides medium for enzymatic activities needed for growth oxygen: Helps in releasing metabolic energy essential growth activities Nutrients: macro and micro elements are required by plants for synthesis of protoplasm and act as a source of energy

root and shoot apical meristems and cambium differentiate and mature to perform a specific function this act leading to maturation is termed as differentiation , cells undergo few to major structural changes in both cell wall and protoplasm eg: To form a tracheal element the cells would lose their protoplasm they form strong elastic lignocellulosic secondary cell walls to carry water to long distance even under extreme tension

the living differentiated cells can regain the capacity of division under certain condition eg: formation of meristems -interfascicular cambium and cork cambium from fully differentiated parenchyma cells

the dedifferentiated cells again lose capacity to divide but mature to perform a specific function eg: secondary xylem secondary pholem and cork