At night, when photosynthesis is not occurring, carbon dioxide elimination is the major exchange activity. During the day, carbon dioxide generated during respiration is used up for photosynthesis, resulting in oxygen release as the major gas exchange activity.
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During the day, plants primarily engage in photosynthesis, actively taking in carbon dioxide (CO₂) through open stomata on leaves. This allows for CO₂ absorption, which, in the presence of sunlight, supports the process of photosynthesis, producing oxygen (O₂) as a byproduct. At night, when photosynthesis is minimal or absent, plants generally close their stomata to reduce water loss through transpiration. While closed stomata conserve water, they limit gas exchange, leading to a decrease in O₂ release and CO₂ uptake. This diurnal pattern reflects the balance between photosynthetic activity and water conservation in plants.