Why are photosynthesis and respiration effects generally ignored during potometer readings?

The reason why the effects of photosynthesis and respiration are generally ignored during potometer readings relates to the scale of their impact compared to the process of transpiration. In a potometer, which measures the water uptake and usage by plants, transpiration (the loss of water vapor from plant leaves) is typically much greater than any water volume associated with photosynthesis and respiration.

Photosynthesis and respiration involve the exchange of gases and can result in minor water losses or gains; however, these changes in water volume are negligible when placed beside the substantial amount of water evaporated through transpiration. Therefore, when interpreting potometer readings, the focus is primarily on transpiration rates, as they provide a clearer and more significant indication of the plant's water use and physiological status. This makes the contribution of photosynthesis and respiration less relevant for practical measurements in this context.