<P> Transpiration is the process of water movement through a plant and its evaporation from aerial parts , such as leaves , stems and flowers . Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism . The remaining 97 -- 99.5 % is lost by transpiration and guttation . Leaf surfaces are dotted with pores called stomata , and in most plants they are more numerous on the undersides of the foliage . The stomata are bordered by guard cells and their stomatal accessory cells ( together known as stomatal complex ) that open and close the pore . Transpiration occurs through the stomatal apertures , and can be thought of as a necessary `` cost '' associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis . Transpiration also cools plants , changes osmotic pressure of cells , and enables mass flow of mineral nutrients and water from roots to shoots . Two major factors influence the rate of water flow from the soil to the roots : the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil . Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem . </P>
<P> Transpiration is the process of water movement through a plant and its evaporation from aerial parts , such as leaves , stems and flowers . Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism . The remaining 97 -- 99.5 % is lost by transpiration and guttation . Leaf surfaces are dotted with pores called stomata , and in most plants they are more numerous on the undersides of the foliage . The stomata are bordered by guard cells and their stomatal accessory cells ( together known as stomatal complex ) that open and close the pore . Transpiration occurs through the stomatal apertures , and can be thought of as a necessary `` cost '' associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis . Transpiration also cools plants , changes osmotic pressure of cells , and enables mass flow of mineral nutrients and water from roots to shoots . Two major factors influence the rate of water flow from the soil to the roots : the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil . Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem . </P>
where can water be lost from a leaf
where can water be lost from a leaf
aerial parts , such as leaves , stems and flowers
aerial parts , such as leaves , stems and flowers