1. Control systems in plants
Chapter 33
Control systems in plants

2. Experiments on plant hormones
Review experiments on phototrophism.

3. Plant hormones

4. The five major types of hormones in plant growth and development
Auxins – stem elongation – apical growth.
Cytokinins – stimulate root growth and germination.
Gibberellins – flower and fruit development.
Abscisic acid – inhibits growth and closes stomata.
Ethylene – promotes fruit ripening.

5. Growth response
Trophism are directed growth responses that a plant has to a stimulus.
Response to light - phototropism
Response to gravity - gravitropism
Response to touch - thigmotropism

6. Biological rhythms
Plants have a circadian rhythm based on the 24-hour period.
Driven by light/dark cycle of day and night.
How are biological clocks set? Synthesis of a protein where production is controlled by feedback control (leading hypothesis).
Photoperiodism –measurement of season by how long day/night cycle is.
Phytochrome light absorbing proteins (red), linked to photoperiodism.