The leaves of certain plants will wither during the day and regenerate in the evening.

In some plants, e.g. balsam, the leaves of plants will wither during the day despite the abundance of water in the soil.

In such cases, the respiratory rate during the day exceeds that of the root system.

Cells, therefore, lose their turgidity.

In the evening or in the middle of the night, the stomata are congested and the temperature is not high, therefore, there is no loss of water by air exchange and the tenderness of the leaves is also obtained and they are straightened.