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