Question

In flowering plants, water is conducted through

• A. Root pressure, capillary action and transpiration pull
• B. Only root pressure
• C. Xylem
• D. None of the above

Answer 1

The correct option is A Root pressure, capillary action and transpiration pull

There are 2 processes that enable the water to move up a plant. They are root pressure and transpiration:

1. Root Pressure: Water moves into the roots. As new water moves into the roots it causes the water to move up the plant. Root pressure is capable, under ideal atmospheric conditions, of pushing water one or two feet above the ground. Since root pressure is not strong enough to move water up very high another process is needed to enable the water to continue up the plant. This is transpiration.
2. Transpiration- Transpiration is the loss of water through the leaves and other parts of the plant. Most transpiration occurs through openings, called stomata, on the underside of the leaves. Water moves, because of root pressure, up into the stem. Because water is being lost out of the stomata of the leaves the water in the stems is being pulled up. Why is this? Because water molecule clings to each other by cohesion. As water molecules cling to each other as they move up the stem and into the leaves they pull the molecules up as they transpire out of the stomata. This is called The Cohesion-Tension Model of water transport in the xylem. As water molecules are stuck together by cohesion the entire column of water in the xylem adheres to the sides of the xylem. It is said that the water in under tension as the column moves up the xylem. At the same time, the xylem tube narrows because of the tension.

So, the correct answer is 'Root pressure, capillary action and transpiration pull'.