Which process is controlled by sunlight for marine plants?

• A. Photosynthesis
• B. Respiration
• C. Transpiration
• D. Fermentation

Answer: (A)

Sunlight drives photosynthesis, the process marine plants use to turn light energy into chemical energy stored as sugars. Chlorophyll absorbs light and powers the light-dependent reactions that generate ATP and NADPH, which then fuel the Calvin cycle to fix carbon dioxide into glucose. Oxygen is released as a byproduct. This is why light availability directly controls how quickly marine plants can synthesize sugars. In contrast, respiration releases energy from sugars and happens whether or not light is present; transpiration mainly concerns water loss in terrestrial plants and isn’t the main energy-producing process in aquatic environments; fermentation occurs in the absence of oxygen and is not driven by light.