Transpiration is the process by which plants use water. The water evaporates through the pores in the leaves during the process of photosynthesis when the pores are open to take in oxygen and carbon dioxide. However, coming in contact with the air causes the leaves to dry out very quickly, which means they do need to replace the water that is lost in this manner.
As part of the process of transpiration, plants draw water from the roots to keep the leaves moist and pliant. This water brings the nutrients from the soil into all parts of the plant and helps it stay cool during the hot weather seasons of the year.
For obvious reasons, transpiration takes place much more quickly during the daylight hours, even though it does take place at night as well. During the day the plant is more susceptible to the heat of the sun and the air is not as humid as it is during the darkness. Photosynthesis is the process by which plants get the food they need from the sun and therefore the daylight hours are the times when this occurs. Light stimulates the leaves to open their stomata and speeds up the process in which the leaves lose water.
Transpiration also occurs more quickly when the sun is hotter, such as in the summer months. The higher the temperature the more water the plant will lose. The process also speeds up when the air is dry because there is not as much humidity to prevent a high rate of water evaporation. The wind also plays a part in transpiration. When there is a breeze, no matter how slight, this dries the air so that the water than evaporated from the leaves is quickly carried away.
The amount of water in the soil around the roots of the plant also affects the rate of transpiration. When plants do not receive much water, either because they are growing wild and there has not been very much rain, or if you do not water your plants as much as you should, the rate of transpiration slows down. This means that the plant is trying to conserve as much water as possible.
Transpiration is a very important part of the growth process in plants. Although the water evaporates mainly from the leaves, it also evaporates from the stem of the plant. This is essential for the health of the plants as it lets them bring up the nutrients and minerals needed to keep the plant growing.