Question

In submerged water plants (eg., hydrilla)

(a) Light is not needed for photosynthesis

(b) Photosynthesis does not occur

(c) Light is necessary for photosynthesis

(d) Carbon dioxide is not required for photosynthesis

Answer 1

The correct option is (c):

Explanation of the correct option:​

1. Light is necessary for photosynthesis and the light that enters the water through the water surface.
   
2. The solar energy enters the water that is trapped by the submerged plant.
   
3. It helps with the process of photosynthesis in this plant and the rate of photosynthesis is lower.
   

Explanation of the incorrect options:

Option (a):

1. ​Without light, photosynthesis does not occur.
   
2. This is because photosynthesis depends on the activation of chlorophyll which occurs in the presence of solar energy.
   

Option (b):

1. Photosynthesis occurs in the submerged plant as well since it is autotrophic.
   

Option (d):

1. ​Carbon dioxide dissolved in water is used up in this process of photosynthesis.
   

Final Answer: In submerged water plants light is necessary for photosynthesis.