14.5 Tropic responses

Define gravitropism

response where parts of a plant grow towards/away from gravity

Define phototropism

response where parts of a plant grow towards/away from direction of light source

Gravitropism & phototropism are both controlled by which chemical

auxin

Auxin
> made in s__ t__
> controls shoot/r__ growth
> d__ thru plant from tip

shoot tip, root, diffuses

Auxin
> u__ d__ in response to light/gravity
> stimulates c__ e__ (longer)

unequally distributed, cell elongation

The shoot has __ve g__

-ve gravitropism

The shoot has __ve p__

+ve phototropism

The root has __ve p__

-ve phototropism

The root has __ve g__

+ve gravitropism

Shoot
> s__ breaks down a__ = ↑conc. on shaded side
> auxin d__: cell e__ = bends towards l__

sunlight, auxin, diffuses, elongation, light

Root
> ↑auxin on b__ side
> auxin = ↓cell g__ = root bends down

bottom, growth

Investigating Gravitropism
1.      Place seedlings in P__ dish w/ damp cotton w__
2.      Leave dish on its s__ in a cabinet (d__) for 2 days
3.      Roots grow __wards, shoots grow __wards; proves gravitropism

petri, wool, side, darkness, down, up

Investigating Phototropism
1.      Cover 2 plants w/ boxes: A w/ window on top; B w/ window on a s__
2.      Expose to l__, leave for 1-2 days
3. Plant A grows v__; plant B grows sideways; proves shoots have +ve p__

side, light, vertically, phototropism