Why do plants need to control the loss of water how is this done?

Transpiration is the major way by which plants loose water (95%). It occurs through the stomata. Water loss is essential for plants because it releases the pressure, aids continuous intake of water by the plant, and allows the water to move to other parts of the plant that need water. Water loss through transpiration is regulated by Guard cells, which help prevent plants from drying out by regulating the opening & closing of the stomata, thus regulating the flow of the water vapor from the leaf tissue.