Question

figure 1. effect of light intensity and growth period on the rate of photosynthesis in sage plants. error bars represent ±2se. using light - filtering cloths, scientists exposed sage plants to four different light intensities. half of the sage plants were exposed to light for 60 days, while the other half were exposed to light for 75 days. the rate of photosynthesis in each plant was then determined (figure 1). which of the following statements best describes the data? a at 100% light intensity, the rate of photosynthesis was higher in plants that were treated for 60 days than in plants that were treated for 75 days. b at 75% light intensity, the rate of photosynthesis was unaffected by an increase in treatment time. c at 50% light intensity, the rate of photosynthesis was the same as the rate of photosynthesis at 75% light intensity, regardless of the length of treatment time. d at 25% light intensity, the rate of photosynthesis was higher in plants treated for 75 days than it was in plants treated for 60 days.

Explanation:

• For option A: At 100% light intensity, the bar for 60 days (dark) is taller than 75 days (white), so A is incorrect.
• For option B: At 75% light intensity, the 75-day bar is shorter than the 60-day bar, so treatment time affected photosynthesis rate; B is incorrect.
• For option C: At 50% light intensity, the bars are shorter than at 75% for both treatment times, so rates are not the same; C is incorrect.
• For option D: At 25% light intensity, the white bar (75 days) is taller than the dark bar (60 days), so D is correct.

Answer:

D. At 25% light intensity, the rate of photosynthesis was higher in plants treated for 75 days than it was in plants treated for 60 days.