<Ol> <Li> Soil </Li> <Li> Roots and Root Hair </Li> <Li> Xylem </Li> <Li> Leaves </Li> <Li> Air </Li> </Ol> <Li> Roots and Root Hair </Li> <P> The water passes from the soil to the root by osmosis . The long and thin shape of root hairs maximizes surface area so that more water can enter . There is greater water potential in the soil than in the cytoplasm of the root hair cells . As the cells surface membrane of the root hair cell is semi-permeable, osmosis can take place; and water passes from the soil to the root hairs . The next stage in the transpiration stream is water passing into the xylem vessels . The water either goes through the cortex cells (between the root cells and the xylem vessels) or it bypasses them--going through their cell walls . After this, the water moves up the xylem vessels to the leaves through diffusion: A pressure change between the top and bottom of the vessel . Diffusion takes place because there is a water potential gradient between water in the xylem vessel and the leaf (as water is transpiring out of the leaf). This means that water diffuses up the leaf . There is also a pressure change between the top and bottom of the xylem vessels, due to water loss from the leaves . This reduces the pressure of water at the top of the vessels . This means water moves up the vessels . The last stage in the transpiration stream is the water moving into the leaves, and then the actual transpiration . First, the water moves into the mesophyll cells from the top of the xylem vessels . Then the water evaporates out of the cells into the spaces between the cells in the leaf . After this, the water leaves the leaf (and the whole plant) by diffusion through stomata . </P>

How water moves from the roots to the leaves