Answer.(a) (i) Gaseous exchanges between plant and the atmosphere. (ii) Plant loses water through stomata which helps in movement of minerals from soil to leaves. (b) Raw materials for photosynthesis: Carbon dioxide, water, chlorophyll and sunlight are the essential raw materials for photosynthesis. (i) Carbon dioxide is a gas, which is released into the atmosphere during respiration. This gas is utilised by the autotrophic plants which enters the leaf through the stomata present on its surface during the process of photosynthesis. (ii) Water is another requirement for photosynthesis, which is transported upward through xylem tissues to the leaves, from where it reaches the photosynthetic cells. This water then splits in the presence of sunlight and chlorophyll. (iii) Chlorophyll is a green pigment in plants, which acts as a catalyst. It is responsible for absorption of the sun’s energy by the plant. The chlorophyll pigments are photoreceptor molecules which play a key role in the photosynthetic process. The different types of chlorophyll molecules are chlorophyll a, b, c, d, e and bacteriochlorophyll; of which chlorophyll a and b are the most common. (iv) Light affects photosynthesis by its intensity, quality and duration. In green light, the rate of photosynthesis is minimum, while in red and blue lights the rate of photosynthesis is maximum. Rate of photosynthesis is higher in plants getting average light of 10-12 hrs a day. The chemical equation for photosynthesis is as follows: