30   10 Some plants are adapted to grow in shady conditions. A study was carried out to compare the effect of growing in different light intensities on rates of photosynthesis of plants. The plants are rated for levels of shade tolerance. Plant seedlings of nine species were grown in either 25% or 5% of full sunlight. All other abiotic factors were controlled. These seedlings were grown for six weeks and then exposed to full sunlight for 15 minutes. The rate of photosynthesis was measured during the exposure to full light. The table shows the results of this investigation for four species of plant. Species Shade tolerance Rate of photosynthesis / a.u. Seedlings grown in 25% of full sunlight Seedlings grown in 5% of full sunlight A Intolerant 410 415 B Intermediate 300 275 C Tolerant 180 210 D Very tolerant 150 215 (a) (i) Determine which species had the greatest percentage change in rate of photosynthesis when grown in lower light intensities. (2) Answer ................................................................ Turn over 31   (ii) The rate of growth for all nine species of plant was also measured. The graph shows the effects of the rate of photosynthesis on the rate of growth of these plants. 500 400 300 200 100 0 Rate of photosynthesis / a.u. Rate of growth / a.u. 200 150 100 50 0 25% light 5% light Explain the effect of light intensity during the first six weeks of growth on the growth rate of these species of plant. 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Devise an investigation to compare the rate of the light‑dependent reaction in shade tolerant and shade intolerant plants grown at different light intensities. 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(Total for Question 10 = 12 marks) TOTAL FOR PAPER = 100 MARKS