Notes For Class 11 Chapter 15 Plant Growth And Development Download In Pdf
Abscission : Shedding of plant organs like leaves, flowers and fruits etc. from the mature plant.
Apical dominance : Suppression of the growth of lateral buds in presence of apical bud.
Dormancy : A period of suspended activity and growth usually associated with low metabolic rate.
Photoperiodism : Response of plant to the relative length of day and night period to induce flowering.
Phytochrome : A pigment, which control the light dependent developmental process.
Phytohormone : Chemicals secreted by plants in minute quantities which influence the physiological activities.
Senescene : The last phase of growth when metabolic activities decrease.
Vernalisation : A method of promoting flowering by exposing the young plant to low temperature.
Growth : An irreversible permanent increase in size of an organ or its parts or even of an individual. Abbreviations IAA Indole acetic acid NAA Naphthalene acetic acid ABA Abscissic acid IBA Indole-3 butyric acid 2.4D 2.4 dichlorophenoxy acetic acid PGR Plant growth regulator
Measurement of growth : Plant growth can be measured by a variety of parameters like increase in fresh weight, dry weight, length, area, volume and cell number.
Phases of growth : The period of growth is generally divided into three phases, namely, meristamatic, elongation and maturation.
(i) Meristematic zone : New cell produced by metotic division at root-tip and shoot tip thereby show increase in size. Cells are rich in protoplasm and nuclei.
(ii) Elongation zone : Zone of elongation lies just behind the meristematic zone and concerned with enlargement of cells.
(iii) Maturation zone : The portion lies proximal to the phase of elongation. The cells of this zone attain their maximum size in terms of wall thickning and protoplasmic modification.
Growth rate : The increased growth per unit time is termed as growth rate. The growth rate shows an increase that may be arithmetic or geometrical.
Differentiation : A biochemical or morphological change in meristemic cell (at root apex and shoot apex) to differentiate into permanent cell is called differentiation.
Dedifferentiation : The phenomenon of regeneration of permanent tissue to become meristematic is called dedifferentiation.
Redifferentiation : Meristems/tissue are able to produces new cells that once again lose the capacity to divide but mature to perform specific functions.
Growth promoting hormones : These are involved in growth promoting activities such as cell division, cell enlargement, flowering, fruiting and seed formation. e.g., Auxin, gibberellins, cytokinins. Growth inhibitor : Involved in growth inhibiting activities such as dormancy and abscission. e.g., Abscisic acid and Ethylene.
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