Question

Study the graph which shows results of three different experiments P, Q and R.

In a few sentences, summarize what the results of these experiments tell you about the factors which limit photosynthesis under different environmental conditions?

• A. In comparison with curve R, curve P was limited by low temperature and low $C{O}_2$ concentration, curve Q was limited by low $C{O}_2$ concentration.
• B. In comparison with curve R, curve P was limited by high temperature and low $C{O}_2$ concentration, curve Q was limited by high $C{O}_2$ concentration.
  
• C. In comparison with curve R, curve P was limited by low temperature and high $C{O}_2$ concentration, curve Q was limited by high $C{O}_2$ concentration.
  
• D. None of the above

Answer 1

The correct option is A In comparison with curve R, curve P was limited by low temperature and low $C{O}_2$ concentration, curve Q was limited by low $C{O}_2$ concentration.

An optimum temperature ranging from 25${}^o$C to 35${}^o$C is required for a good rate. At temperatures around 0${}^o$C the enzymes stop working and at very high temperatures the enzymes are denatured. Since, both the stages of photosynthesis require enzyme activity, the temperature has an affect on the rate of photosynthesis. In the atmosphere, the concentration of carbon dioxide ranges from 03 to 04 %. However, it is found that 0.1% of carbon dioxide in the atmosphere increases the rate of photosynthesis significantly. In comparison with curve R, curve P was limited by low temperature and low CO${}_2$ concentration and curve Q was limited by low CO${}_2$ concentration compared to curve P but not low temperature.
Therefore, the correct answer is option A.