A single plant can transpire at different rates over the course of a day, depending on a number of factors, including temperature, relative humidity, wind and soil moisture. There are also species-specific differences, which can be broadly classified by the type of photosynthesis: C3, C4 or Crassulacean Acid Metabolism (CAM).
Transpiration rate is a function of stomatal opening. Since plants require stomata to be open to photosynthesize, plants lose water through transpiration when photosynthesizing. Plants that are better adapted to water-stressed environments reduce their transpiration rate in comparison to a C3 plant by using C4 or CAM, fixing a higher number of carbon molecules per unit of water lost. Other adaptations to reduce transpiration rates include reducing leaf number and leaf size or increasing the thickness of a leaf cuticle.