Question

Read the following passage and answer the questions that follow:

Not all plants carry out photosynthesis by the same mechanism. In most plants, it depends directly on gaseous carbon dioxide that diffuses into the leaf. However, some plants can store carbon dioxide in the vacuole of the leaf cells as part of a complex carbon compound. This compound is transported to the chloroplast and releases carbon dioxide when required for photosynthesis. This special mechanism is believed to have evolved as an adaptation in such plants which do not open stomata during the daytime to conserve water for survival in dry conditions (desert conditions).

Attempt either (a) or (b):

1.  
   1. Which process in these plants is minimised to help the plants survive in dry conditions?
   2. Which part of the leaf is responsible for exchange of gases during photosynthesis?
      OR
2. 
   
   1. List the events that occur during the process of photosynthesis.
   2. When are such desert plants likely to take in carbon dioxide from the environment, unlike other plants?
   3. Draw a labelled diagram of stomata with open stomatal pore.

Answer 1

1.  
   1. Transpiration is minimised. These plants keep their stomata closed during the daytime to reduce water loss through transpiration.
   2. Stomata are responsible for the exchange of gases.
      OR
2.  
   
   1. 
      
      • Absorption of light energy by chlorophyll.
      • Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen.
      • Reduction of carbon dioxide to form carbohydrates (glucose).
   2. These desert plants take in carbon dioxide at night, when the stomata are open.
   3.