NEETBotanyPhotosynthesis in Higher Plants
If a healthy, actively photosynthesizing plant is suddenly transferred from a well-lit environment into a completely dark room, what will be the immediate to short-term fate of the biosynthetic phase (sugar synthesis) in its leaves?
Options
- AIt continues indefinitely because the biosynthetic phase is completely independent of light
- BIt stops immediately because the absorption of light by chlorophyll ceases
- CIt stops immediately due to the lack of CO ₂ availability in the dark
- DIt continues for some time and then stops due to the depletion of ATP and NADPH
Correct answer
D. It continues for some time and then stops due to the depletion of ATP and NADPH
Step-by-step solution
The biosynthetic phase (dark reaction) does not directly require light, but it is strictly dependent on the products of the photochemical phase (light reaction), which are ATP and NADPH. When a plant is suddenly moved to darkness, the light reaction stops immediately, halting the further production of ATP and NADPH. However, the biosynthetic phase will continue for a short duration using the existing pool of these molecules. Once the available ATP and NADPH are exhausted, sugar synthesis will also stop. Answer: It