The pressure created by water movement into the root xylem is unlikely to move water over significant heights. Plants employ another strategy, possibly involving transpiration and cohesion, to move water upwards in the xylem to the highest points of the plant body.
Why is the pressure generated by the movement of water into the root xylem alone insufficient to move water to the upper parts of plants, and what strategy do plants use to achieve this movement?
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The pressure generated by the movement of water into the root xylem, known as root pressure, is insufficient to move water to the upper parts of plants, especially in tall trees. Gravity counteracts root pressure, limiting its effectiveness in lifting water to great heights. To overcome this limitation, plants primarily rely on transpiration-driven tension. As water evaporates from the leaves through stomata, a negative pressure is created, pulling water upward through the xylem vessels. This cohesive and adhesive property of water, combined with capillary action and the strength of xylem vessels, enables plants to effectively transport water against gravitational forces to their upper parts.