tropic responses Flashcards
1
Q
define gravitropism
A
response in which parts of a plant grow towards or away from gravity.
2
Q
Explain the role of auxin in controlling shoot
growth
A
- plant hormone auxin chemically controls growth near tips of shoots
- made in the shoot tip
- diffuses through the plant from shoot tip
- unequally distributed in the response to light & gravity
- stimulates cell elongation
2
Q
define phototropism
A
response in which parts of a plant grow towards or away from the direction of the light source
3
Q
in shoots
positive phototropism
A
- more auxin accumulates on the side in the shade
- stimulates cells to elongate faster on the shaded side, so shoot bends towards light.
4
Q
in shoots
negative gravitropism
A
- when shoot grows horizintally, gravity produces unequal distribution of auxin, more on the bottom side of tip.
- this stimulates the cells of the bottom side to elongate faster, bending the shoot upwards, against the force of gravity.
