Plants need

, minerals and

to stay alive.

Water absorbed by

which are extensions of

Water enters these cells through the process of

and passes from cell to cell (again through the same process) until it reaches a vessel called the

Xylem vessels carry

and

from the roots to the rest of the plant in an

direction. Xylem vessels take water and minerals to the leaves.

Xylem vessels consist of

hollow cells. They are thick, strong tubes, because they are strengthened by

Water moves from the Xylem into the

mesophyll cells and then the water on the surface of

and

mesophyll

(inside the leaf)

evaporates and then

out of the

in the leaf. More water is drawn out of the xylem cells inside the leaf to replace what's lost. As the xylem cells make a continuous tube from the leaf, down the stem to the roots, this acts like a drinking straw, producing a flow of water and dissolved minerals from roots to leaves.

Stomata are little

(usually) on the

The opening and closing of a stomata is controlled by the two

You can measure the transpiration rate by using a Bubble potometer or a

Weight potometer

.

Bubble

potometers work

as water moves up through the plant the air bubble moves along the scale giving a measure of water absorbed by the plant over time and hence the transpiration rate.

Weight

potometers work by putting a leafy shoot in water with a layer of oil over the surface to prevent loss of water by evaporation. The test tube and shoot are weighed at the start and then again after a few hours. Any difference in weight will indicate loss of water by the shoot (due to transpiration).

The sugars are moved from the leaves through tube-shaped vessels called

Unlike xylem, the cells that make this up are alive. The sugars are moved from the leaves through tube-shaped vessels called p _ _ _ _ _. Unlike xylem, the cells that make this up are alive. Phloem consists of two main types of cell.

cells are linked top and bottom with each other and do not contain a nucleus. It is through these cells that the sugar flows. Each cell is linked to the next by a perforated cell wall called a

Each sieve tube cell has an accompanying

cell. These do contain a nucleus and are thought to control the flow of sugars in the sieve tubes.