plant harmones by dilip kumar chandra

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