Plant Responses/Behavior

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
• 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