Water Balance ; will spend most of the time on concept of water potential.

1. Review the properties of water: polarity, hydrogen bonds, adhesion, cohesion,.

2. Review emergent properties from above: surface tension, tensile strength

3. fundamental transport processes: diffusion, osmosis, mass flow

4. introduce concept of water potential = potential energy of water expressed as units of pressure (psals or mpa) Water moves from high to low potential spontaneously.

5. three factors which influence water potential: pressure potential, osmotic potential, gravity potential

6. Plants can manipulate osmotic and pressure.

7. can measure water potential and directly assess water status of a plant.

8. Water in soils also driven by water potential. Matric potential - soil property. Water always under tension in soils.

9. Cohesion-tension theory of water movement in plants

10. Osmotic condition of soils: salty soils appear drier to plants trying to extract water.