How Do Plants Move Water from Roots to Leaves

How Do Plants Move Water From Roots to Leaves?

TRANSPIRATION!

Transpiration depends on 3 concepts:

1. Osmosis: Water moves from areas of high concentration (amount of water in the space) to an area of low concentration across a membrane until a balance is reached. It does not require energy.

2. Cohesion: Because water is polar (oxygen atom is a little bit negative, hydrogen is a little positive), it sticks to itself.

3. Tension: A pull felt in a tube.

http://www.youtube.com/watch?v=mc9gUm1mMzc

The Cohesion-Tension Theory of transpiration states that:

In the leaf, when the guard cells open, water evaporates out of the guard cells. These cells then have a lower concentration

of water than the surrounding

cells, so water moves into the guard cells through osmosis. The surrounding cells pull water in from other cells, until the pull is felt in the xylem, which is a tube of water. Because of

cohesion, when water is pulled out of the top of the xylem, it pulls (tension) the whole tube of water up the xylem from the roots.

The root cells donate their water into the xylem, which lowers their concentration. When their concentration becomes lower than the concentration of water in the soil, water moves into the root.