A class measures the rate of photosynthesis of pondweed by watching bubbles rise from the cut stem. What are those bubbles, and what do they show?

Explicación

The gas the reaction gives off comes out of the cut stem as bubbles, so counting them over a fixed time tracks how fast the reaction is running. The common error names the gas the plant absorbs instead, but that one is taken in from the water around the shoot and would never appear as bubbles leaving it.