“The task of the excellent teacher is to stimulate apparently ordinary people to unusual effort. The tough problem is not in identifying winners: it is in making winners out of ordinary people.”
Feb 8, 2011
Movement of water from soil to leaves
i) from soil to roots
- water diffuse into the cell of root hairs by osmosis
- concentration of water in the cell is lower than outside the cell/soil
- cell becomes hypotonic to the adjacent cells by osmosis
- osmosis goes on until water molecules reach the xylem vessels
ii) roots up the stem
- transpirational pull draws water upwards
- cohesive forces between water molecules
- adhesive forces between water molecules and the wall of xylem vessels
- generates capillary action
iii) from the leaves to the atmosphere
- water evaporates from the surface of the mesophyll cells into the air spaces/surrounding
- water which is lost, is replaced by water in the xylem by osmosis
- water vapour diffuses out/evaporates into the atmosphere through the stomata
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