Which observation indicates photosynthesis is occurring in aquatic plants?

Which observation indicates photosynthesis is occurring in aquatic plants?

• A. No gas is produced
• B. Oxygen bubbles visible for counting
• C. Carbon dioxide bubbles visible for counting
• D. Oxygen is absorbed, not released

Answer: (B)

Oxygen production is the telltale sign here. During photosynthesis, water is split to release oxygen gas, so aquatic plants that are photosynthesizing will emit O2 as bubbles. Seeing those oxygen bubbles visibly indicates photosynthesis is occurring, because the plant is converting light energy into chemical energy and producing the gas as a byproduct. The other observations don’t fit this process. If no gas is produced, it could mean little or no photosynthesis or that conditions aren’t right. CO2 bubbles would mean carbon dioxide is being released, which doesn’t happen in photosynthesis (CO2 is consumed, not produced). Oxygen being absorbed would suggest respiration or oxygen uptake, not photosynthesis.

Oxygen production is the telltale sign here. During photosynthesis, water is split to release oxygen gas, so aquatic plants that are photosynthesizing will emit O2 as bubbles. Seeing those oxygen bubbles visibly indicates photosynthesis is occurring, because the plant is converting light energy into chemical energy and producing the gas as a byproduct.

The other observations don’t fit this process. If no gas is produced, it could mean little or no photosynthesis or that conditions aren’t right. CO2 bubbles would mean carbon dioxide is being released, which doesn’t happen in photosynthesis (CO2 is consumed, not produced). Oxygen being absorbed would suggest respiration or oxygen uptake, not photosynthesis.