1. Plant Responses/Behavior
Cell division, germination, cell differentiation, flowering, fruit ripening, root growth, branching, etc

2. Tropisms
Growth response toward (+) or away from (-) a stimulus

3. Phototropism Response to light Gravitropism Response to gravity
Shoots (stems) + phototropism
Roots – phototropism
Gravitropism
Response to gravity
Shoots (stems) – gravitropism
Roots + gravitropism
Thigmotropism
Response to touch

4. Other Responses Apical dominance
Apical bud/shoot represses lateral growth
Photoperiodism
Plants detect & respond to periods of darkness
Abscission
Aging of leaves
Circadian rhythms
Cycles of daily behaviors
Controlled by endogenous clocks
Sleep movements

5. (varies)
Need specific amt of uninterrupted darkness SHORTER than critical night length
Need specific amt of uninterrupted
Darkness, MORE than critical night length

6. So what makes plants behave the way they do? HORMONES!!!!
Chemical signals produced in one part of an organisms that influence another
Triggers a response at the cellular level, relies on specific hormone receptor binding
Effective at extremely small concentrations
Overall behavior/growth is a result of a combo of all hormones

7. Experimenting w/ Hormones
Conclusions:
Darwin-chemical in tip, light required
Boysen-Jenson-signal is mobile,passed thru agar

8. Went Experiments:
Chemical is produced in tip,
Concentrates on dark side,
Causes elongation of cells

9. The answer is…..
AUXIN

10. Mechanism of Auxin

11. Stimulatory Hormones Auxins Elongation of cells in developing shoots
Induces cell division in vascular cambium
Promotes fruit growth
Responsible for photo & gravi tropisms

12. Stimulatory cont….
Cytokinins
Produced in actively dividing tissues(germinating seeds, fruits, roots)
Delay senescence
Controls differentiation (w/ auxin)

13. More stimulation… Gibberellins
Produced in roots, stimulate stem & leaf growth
Promote fruit development (W/ auxin)
Stimulate germination (if environmental conditions are right)

14. Inhibitory Hormones Abscisic acid
Prepares for dormancy by inhibiting vascular cambium & slowing bud growth
Keeps seeds dormant
Produced during water stress (causes guard cells to lose water, closing stomata)

15. Inhibitory continued…
Ethylene
Only gaseous hormone
Inhibits cell growth & elongation in all plant organs
Causes senescence
Fruit ripening-degrades cell walls, reduces chlorophyll
Leaf abscission-degrades cell wall between stem & petiole

16. Even more plant behaviors (and you thought they were boring!)
O2 deprivation
Release of ethylene from roots, holes form
High salt
Produce extra solutes
Heat
Heat shock proteins bind to enzymes & prevent denaturing
Cold
Synthesize more unsaturated FAs
Herbivores
Pathogens
Anti-microbial compounds, alarm chemicals, PR genes