A green plant absorbs a toxic substance which inhibits the calvin cycle? how would this most likely affect the light reactions

The Calvin cycle is the second stage of photosynthesis, taking place in the stroma of the chloroplasts. It is not directly involved in the light reactions of photosynthesis, which occur in the thylakoid membrane. The light reactions involve the absorption of light energy to produce ATP and NADPH, which are then used in the Calvin cycle to fix carbon dioxide.

If a toxic substance inhibits the Calvin cycle in a green plant, the most likely effect on the light reactions would be an accumulation of energy-carrying molecules like ATP and NADPH. This is because the Calvin cycle utilizes these energy carriers to fix carbon and produce sugars. If the Calvin cycle is inhibited, the energy carriers produced in the light reactions would not be used, and their levels may increase within the chloroplast.

However, it's important to note that the direct effect on the light reactions depends on the specific nature of the toxic substance and its mode of action. Some toxins may directly impact the thylakoid membrane or other components involved in the light reactions, leading to a disruption in the production of ATP and NADPH. The overall impact on the plant's photosynthetic process would be determined by the specific mechanisms and targets of the toxic substance.