First 264 words of the document:
01 January 2011
...then Up the Xylem and Out at the Leaves
Xylem vessels transport water all around plant
At leaves, water leaves xylem and moves into cells mainly by apoplast pathway
Water evaporates from cell walls into spaces between cells in leaf
When stomata (tiny pores in surface of leaf) open, the water moves out of the leaf (down the
water potential gradient) into the surrounding air
The loss of water from a plant's surface is called transpiration
Water Moves Up a Plant Against the Force of Gravity
The movement of water from roots to leaves is called the transpiration stream
Mechanisms that move the water include cohesion and tension
These help water move up plants, from roots to leaves, against the force of gravity
1. Water evaporates from the leaves at the top of the xylem (transpiration) .
2. This creates a tension (suctions), which pulls more water into the leaf.
3. Water molecules are cohesive (they stick together) so when some are pulled into the leaf
So, the whole column of water in the xylem, moves upwards
Adhesion is partly responsible for the movement of water.
1. Water molecules are also attracted to the walls of the xylem vessels.
2. Helps water rise through xylem vessels.
Water Enters a Plant through its Root Hair Cells
1. Bit of the root that absorbs water is covered in root hairs.
These increase the root's surface area, speeding up water uptake