plant harmones by dilip kumar chandra
TRANSCRIPT
Controls of growth, development Controls of growth, development and movementand movement
By Dil ip Kumar Chandra
� Cell division.Cell division.� Cell enlargment.Cell enlargment.� Cell differentiation. Cell differentiation.
Primary growthPrimary growth
Apical meristemApical meristem
Leaf primordiaLeaf primordia
Forming axillary budForming axillary bud
Ground meristemGround meristem
protodermprotoderm
procambiumprocambium
Secondary growthSecondary growth
xylemxylem
Phloem withPhloem withbands of fibersbands of fibers
Vascular cambiumVascular cambium
Ray parenchymaRay parenchyma
corkcork
� Scarification� mechanical� chemical� heat
� Mobilization of reserves
� Turgor movements (changes in turgor pressure in selected cells)
� Growth movements (elongation of selected cells in response to stimulus)� phototropism� geotropism� thigmotropism
Directional movements in response to a directional stimulus
GeotropismGeotropism
� Signal molecules produced at specific locations.� Occur in low concentrations.� Cause altered processes in target cells at other
locations.
Artificially synthesized substances which produce hormone like responses
� Auxins� Gibberellins� Cytokinins� Abscisic acid� Ethylene
Auxin associated with phototropism - early experimentsAuxin associated with phototropism - early experimentsdemonstrate tip as receptor.demonstrate tip as receptor.
Demonstration of transported chemicalDemonstration of transported chemical
� Discovered as substance associated with phototropic response.
� Occurs in very low concentrations.� Isolated from human urine, (40mg 33 gals-1)� In coleoptiles (1g 20,000 tons-1)
� Differential response depending on dose.
� abscission - loss of leaves� flower initiation� sex determination� fruit development
infecteduninfected
� General cell elongation.� Breaking of dormancy.� Promotion of flowering.� Transport is non-polar, bidirectional producing
general responses.
� Promotes cell division.� Morphogenesis.� Lateral bud development.� Delay of senescence.� Stomatal opening.� Rapid transport in xylem stream.
� General growth inhibitor.� Causes stomatal closure.� Readily translocated.� Produced in response to stress.
H H \ / C = C / \ H H
� Gaseous in form.� Rapid diffusion.� Affects adjacent individuals.� Fruit ripening.� Senescence and abscission.� Interference with auxin transport.� Initiation of stem elongation and bud
development.
� Constitutive enzymes - always present but level of hormone can affect level.
� Adaptive enzymes - formed or activated as a result of the presence of a hormone.
Interaction of cytokinin and auxinInteraction of cytokinin and auxinin tobacco callus tissuein tobacco callus tissue