Plant hormones Questions Flashcards
A germinating seed has a root that grows downwards. A is at the top of the root, while B is at the bottom.
a) State where the concentration of auxin is higher, A or B.
b) Explain how this has caused the root to grow downwards.
a) It is higher at B.
b) In the roots, a higher concentration of auxin inhibits cell elongation. This means that the cells at A elongate more than the cells at B so the root grows downwards.
Explain how the auxin helps a shoot to grow towards light shining from one side.
When a shoot gets light from one side auxin from the rip moves to the shaded side of the shoot
This causes cells on the shaded side to elongate more than those on the light side, so the shoot will curve as it grows so that the tip points towards the light
Explain the advantage of gravitropism to plant roots.
Plant roots are positively gravitropic/grow downwards towards gravity.
Growing downwards increases the chance that the root will reach soil, which provides support, as well as water and nutrients.
State where auxin is produced
in the shoot tip
Jennifer grows some oat seedlings in a cardboard box with a light source on one side. In A the tips of the seedlings have been cut. In B a foil cap has been placed over the tip. Jennifer allowed the seedlings in C to grow unaltered.
Predict and explain the results of Jennifer’s investigation.
- A didn’t grow at all/no response to light
- the tips were cut off, no auxin was produced as it is normally produced in the tips
- auxin causes cells to elongate
- no elongation as no auxin
- B grew straight upwards
- auxin diffuses away from light
- auxin was still produced as the tips are intact
- the ends of the shoot recieved no light so auxin diffused evenly down the shoot
- the cells elongated evenly
- C grew towards the light because the tips are intact
- the ends are uncovered, and the auxin produced in the tips diffuses away from the light and down the shoot
- the cells on the shaded side elongate, and it grows towards the light
