Plant HormonesPlant Hormones

Plant growth regulatorsPlant growth regulators

What does a plant need to respond to in its

environment?

•Light•Water•Gravity

Positively phototrophicPositively geotrophic

Positively hydrotrophic

How are plant growth factors different from animal

hormones?

• They exert an influence by affecting growth

• Produced and released by cells through out the plant rather than organs.

• They affect the tissues or nearby tissues that release them, not distant target organs.

Examples

• Auxin – effects growth of the plant – example = IAA (the one you need to know about.

• Cytokinins - growth control in fruit • Ethylene - promote ripening on the

tree • Gibberellins – promote seed

germination

How IAA works

Experiments

• What doe these prove?

• Page 160 has the final lot of experiments explaining the action of IAA

geotropism