Chapter 27: Control Of Growth And Response In Plants Flashcards
stimulus from one direction
Result in uneven growth
Tropisms
Results in growth
Positive tropism
Toward stimulus
Negative tropism
Away from stimulus (sun)
Mechanism:
Reception- transduction - response
Phototropism
Light reaction by buds or stem
Pigment
Photoreceptor
Hormone auxin
Redistributed to shaded side of shoot, causes uneven growth
Geotropism (gravitropism)
Response to gravity
Shoots grow up
Negative geotropism
Roots grows down
Positive geotropism
Root cap contains
Statolith
Amyloplast settles to bottom of cell, then…
ER to realeae ca2+ —> auxin release and stimulates growth
Auxin:
Inhibits root cells -> growth top- downward movemet
Stimulates stem cells-> growth bottom- upward movement
Shoots that grow horizontal
Auxin moves to lower side causing elongation (stolons, strawberries)
Thigmotropism
Coiling or in response to touch- requires atp
Thigmomorphogenesis
More wind stimulation- less growth
Caused by increase in ethylene-> inhibits growth
Hydrotropism
Response to water by the roots. Roots grown down toward water source
Thermotropism
Response by the shoot system to hear
Excessive heat causes
The stomata to close
Seismonastic movements or rapid leaf movements
Loss of turgor pressure at the petiole base of some plants from touch or wind. K+ pumped out along with water
Mimosa plant
Touching leaves causes protons to leave and cause water to leave. (Seismonastic movements)
Nyctinastic movements
In the evening leaflets fold together and the whole leaf droops downward until sunrise. Movements guided by circadian rhythm
5 major plant hormones:
- Auxin
- Cytokins
- Ethylene
- Abscisic acid
- Gibberellins
1 minor plant hormone is oligosaccharins
