Required Practical 8 - Plant Responses

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

• 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)

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

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

What growth substance in plants is affected by light?

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

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

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