Transport

1. Water evaporates from cell walls in the leaf.
2. More water is drawn out of xylem vessels and through cell walls by capillary action.
3. This generates tension, or negative pressure, in the xylem.
4. Cohesion between water molecules keeps the column continuous, so the tension pulls water up from the roots.

Adhesion between water and hydrophilic cell walls helps too. The plant spends no ATP on this movement, because the Sun supplies the energy for evaporation.

The epidermis forms the outer layer, and the cortex lies inside it. Vascular bundles form a ring near the outside. In each bundle, xylem carries water and ions towards the centre of the stem and phloem, which carries sugars, is on the outer side.

The epidermis has root hairs for absorbing water. The large cortex surrounds the central vascular tissue. Xylem forms a star or cross shape at the very centre, and phloem lies between its arms.

When you draw either plan diagram, show the outlines of tissues, not cells. Keep to the proportions of the micrograph, and label each boundary.