RP: Plant hormones

Question 1

How can we investigate the effct of light on seedlings?

Answer 1

1.) Soak 3 cotton wools in the same volume of water.
2.) Place 10 seeds on each cotton wool.
3.) Water the seeds everyday with the same volume of water.
4.) Place one dish in full sunlight, one in partial light, and one in full darkness.
5.) Measure the height of each seedling each day for 5 consecutive days.
6.) Calculate the mean height of the seedlings for each day (in all 3 different conditions.)

Question 2

What would you expect the seedlings in full darkness to do?

Answer 2

• Their stem grows (they increase in height) in order to try and reach sunlight.
• Auxin will go to the “dark sides” of the plant and encourage growth.

Question 3

How can we investigate the effects of gravity on seedlings?

Answer 3

• Put a dish (containing seedlings) on its side.
• The plant will grow upwards (against gravity.)
• The roots will grow downwards (in the direction of gravity.)
• Auxin inhibits growth in roots (on the lower side) - the upper side grows more quickly and this causes the roots to move downwards.

Question 4

What are the control variables when investigating the effect of light on seedlings?

Answer 4

• Volumes of water used.
• Number of seedlings used.
• Types of seedlings used.