Required practical 8 - Plant responses

Question 1

Describe how you would investigate the effect of light on the growth of newly germinated seedlings

Answer 1

• Incubate seeds in 3 petri dishes and allow them to germinate.
• Place one dish in full sunlight, one in partial sunlight and one in complete darkness.
• Measure the height of each seedling every day for a week and calculate the mean height for each day.
• Plot graph of mean seedling height (y) against day (x).

Question 2

Which group of seedlings would you expect to grow the most and why?

Answer 2

The group in full sunlight - light is required for photosynthesis and these plants will not have light intensity as a limiting factor.

Question 3

What growth substance is affected by light?

Answer 3

Auxins - the distribution of auxins in seedling stems is affected by light. This impacts the seedling’s direction of growth.

Question 4

Why is it necessary to find the mean height of the seedlings?

Answer 4

Some seedlings may be much shorter/longer than others in the same dish - calculating a mean makes the values more representative and allows comparison between groups.