Water evaporates from the mesophyll cells into air spaces due to heat from the sun, This leads to water vapour leaving the plant through the stomata, Water forms hydrogen bonds between one another and stick together (cohesion), This means water forms a continuous unbroken column from the mesophyll cells down the xylem, A column of water is pulled up the xylem as a result of transpiration (transpiration pull), This 'Transpiration pull' puts the xylem under tension - forming a negative pressure in the xylem - hence the 'cohesion tension theory', Water is pulled from the roots into the stem., Water moves from the root hair cells to the root cortex to the stem by osmosis.

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