Factors affecting photosynthesis Original Scenario-Based Practice

Questions

1. 1.

   Astrobotanists aboard a deep-space habitat cultivate a leafy crop inside a sealed growth pod supplied with constant high-intensity red-blue light and atmospheric carbon dioxide (0.04%) at 25°C. When the team doubles the light intensity, the rate of oxygen release and carbohydrate accumulation remains completely unchanged, but elevating the carbon dioxide concentration to 0.12% promptly triggers a significant rise in photosynthetic output. Subsequently, when the pod’s temperature is reduced to 4°C while keeping the elevated carbon dioxide and light levels intact, the photosynthetic rate plummets toward baseline. Based on these observations, which deduction correctly explains the factors governing photosynthesis in this system?

   • A) Light intensity initially limited photosynthesis because photosynthetic pigments were operating below photon saturation.
   • B) Reducing the temperature to 4°C restricted photosynthesis primarily by degrading chlorophyll molecules and halting photolysis.
   • C) Carbon dioxide was the initial limiting factor, and low temperature later restricted the rate because Calvin cycle enzymes require adequate thermal kinetic energy to catalyze reactions.
   • D) Carbon dioxide availability directly accelerates the light-dependent reactions, whereas temperature exclusively regulates photon absorption in photosystem II.

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