At what times is there a no net gaseous exchange between leaves and the atmosphere?

Explanation

Dusk there is no net gaseous exchange between leaves and atmosphere. At dawn and dusk,when light intensity is low, the rate of photosynthesis and respiration may, for a short time, equal one another. Thus the oxygen released from photosynthesis is just the amount required for cellular respiration. Also, the carbon dioxide released by respiration just equals the quantity required by photosynthesizing cells. At this moment there is no net gas exchange between the leaves and the atmosphere. This is termed as compensation point.