When does transpiration primarily occur?

Transpiration primarily occurs during the day when sunlight is available. During this time, plants carry out photosynthesis, a process that uses sunlight to convert carbon dioxide and water into glucose and oxygen. To perform photosynthesis effectively, plants need to absorb carbon dioxide from the air, which they take in through small openings in their leaves called stomata.

During the day, stomata open to allow carbon dioxide in, and as a result, water vapor escapes from the plant through these openings. This loss of water from the leaves helps to create a pressure difference that assists in drawing more water and nutrients up from the roots through the plant's vascular system. Therefore, transpiration plays a key role in maintaining this flow of water and nutrients, and it is most efficient when the stomata are actively open during daylight hours.

In contrast, during the night, stomata often close to conserve water, leading to reduced transpiration, while rainy days typically involve less transpiration due to higher humidity levels and possibly closed stomata during excess moisture. During periods of drought, plants may also close their stomata to prevent water loss, further limiting transpiration.