Question

Immediately after light becomes unavailable, the biosynthetic process

• A. continues for some time and then stops
• B. stops and starts again if the light is made available
• C. stops permanently if the light is not made available in future
• D. all of the above

Answer 1

The correct option is D all of the above

Photosynthesis is the process by which plants make their food in the form of glucose. The process of photosynthesis consists of two phases - light dependent and light independent phase.

During the light dependent reaction, light is entrapped by the chlorophyll to synthesise ATP and NADPH. During the light independent reaction, also called the biosynthetic phase, glucose synthesis takes place.

The biosynthetic phase occurs in the stroma of the chloroplasts. These reactions do not require light directly but depend on products of light reaction like ATP and NADPH. Hence, in absence of light after some time, the ATP and NADPH are no longer available. In the absence of ATP and NADPH, the Calvin cycle (biosynthetic phase) stops and there is no synthesis of glucose for that period of time. When the light is provided again after some time, the light reactions take place leading to the synthesis of ATP and NADPH. With the availability of ATP and NADPH, the light independent reaction becomes operational again. So, the light independent reaction stops if the light is absent and starts again if the light is made available.