the genetic basis of growth and development
Post on 25-Feb-2016
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The Genetic Basis of Growth and Development
Plants are made up of
• cells• tissues• organs
Plants have specialized tissues called meristems
• Shoot apical meristem (SAM)
• Intercalary meristem• Root apical meristem
(RAM)• Lateral meristems:
pericycle, vascular cambium
Plants grow by cell
• division• expansion• differentiation
Plant development is controlled by hormones
• Auxin:stimulates growth and cell division• Gibberellins:stimulates stem growth and
seed germination• Cytokinins:regulates cell division and
senescence• Abscisic Acid:responds to osmotic stress,
inhibits germination, closes guard cells
More Hormones
• Ethylene:regulates fruit ripening and flowering, responds to stress
• Jasmonic Acid:responds to insect attacks turning on plant defenses
• Brassinosteroids: affect stem elongation, pollen tube growth, leaf bending and xylem differentiation
Plant development is affected by the environment
• Phototropism (light)• Gravitropism (gravity)• Thigmotropism (touch)• Nyctinastic movement (light)• Thigmonastic movement (mechanical)
Environmental Influences
• Circadian Rhythms (biological clocks set by light)
• Dormancy (temperature, light & water)• Vernalization (cold induction of flowering)• Stratification (cold induction of
germination)• Photoperiodism (germination and
flowering)
Photoperiodic regulation of flowering
Genetic control of flowering
Signal transduction by hormones or environmental signals
Genetic modification can redirect developmental processes
• Male sterility for hybrid seed production• Fruit ripening• Senescence• Delaying seed pod splitting• Flowering
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