Transport of water in plants
Cacti are typical xerophytes.
Plants are put into categories according to there adaptation to water availability.
Mesophytic plants are not especially adapted to low water/high temperatures. If water is lost (by transpiration) faster than it is lost then wilting results. The cells become flaccid. The stomata close as a result of the guard cells becoming flaccid. This helps to prevent further water loss. As the leaves fold up as the plant wilts it also helps to remove some of the leaf surfaces from the direct effects of the sun.
Transpiration itself helps to keep plants cool by the evaporation of water, in a similar way to the way sweating helps to cool down the skin of mammals.
Most mesophytic plants maintain a temperature slightly higher than the air temperature if the air temperature is below 25*C and lower than the air temperature if it rises above 30*C.
Click on next to start the slide show on xerophytes.