2016年4月3日 星期日

F4 Biology 2nd Term WS 09 ans: 9 Nutrition and gas exchange in plants II

9   Nutrition and gas exchange in plants II
2nd Term WS 09

1     (a)   As light intensity increases from 0 to 500 arbitrary units, the rate of photosynthesis of the plant increase                                                                                                                        1
              More carbon dioxide is taken in by the plant for photosynthesis                                         1
              while the amount of carbon dioxide released in respiration remains unchanged.               1
      
       (b)   At light intensity of 400 arbitrary units, the rate of respiration of the plant is higher than the rate of photosynthesis.                                                                                                          1
              More food is consumed in respiration than is produced in photosynthesis.                         1

2     (a)   The leaf is thin.                                                                                                                    1
              This reduces the diffusion distance of the gas needed for photosynthesis (i.e. carbon dioxide) from the atmosphere to cell X.                                                                                             1
              There are many air spaces among spongy mesophyll cells.                                                  1
              This allows carbon dioxide to diffuse freely to cell X.                                                       1
              (or other reasonable answers)

       (b)   In the daytime, the rate of photosynthesis of the leaf is higher than
              the rate of respiration.                                                                                                           1
              There is a net release of oxygen from the leaf cells.                                                             1

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