1. Irrigation and Plant Physiology

2. The basis of irrigation
Soil
Plant
Evapotranspiration
Plant requirements

3. Photosynthesis http://www.youtube.com/watch?v=IlmgFYmbAUg
Exchanges of gases and water vapors.
Sugar synthesis

4. Photosynthesis light reaction
Whitehead & Gower, 2001

5. The stomata

6. The Stomata

7. Stomata structure

8. Opening of the Stomata Controlling factors Lights
Plant water potential
Environmental conditions:
atmosphere humidity
Co2 concentration
temperature

9. Light Lights is electromagnetic radiation
It is the energy source for the photosynthesis.
P.A.R. – Photosynthesis Active Radiation is at the range of visible light nm

10. Why do plants are green
Which light is corresponded to wave length of 550 nm?
Peaks of absorbents 430, 680 nm

11. Light
It is not possible to have photosynthesis without light, therefore when there is no light the stomata is closed

12. Transpiration process
Transpiration is the process of evaporation or vapor transfer from the plant to the atmosphere through the stomata
Transpiration has two stages:
The vaporization of liquid water in the stomata
Transfer of water vapors from the stomata to the atmosphere
Factors that control the rate of transpiration
VPD
Stomata conductance
Wind speed

13. Vapor transfer What is the driving force for vapor transfer?
VPD – Vapor Pressure Deficit
If the vapore pressure in the atmosphere is equal to the VP in the stomata transpiration rate is 0.
Wind accelerate the rate of vapor transport
Under dry and windy conditions we expect high transpiration rate. Knowing the weather forcast can help us plan irrigation.

14. Other factors CO2 Temperature ABA – Abscisic Acid
Abscisic acid is also produced in the roots in response to decreased soil water potential and other situations in which the plant may be under stress. ABA then translocates to the leaves, where it rapidly alters the osmotic potential of stomatal guard cells, causing them to shrink and stomata to close.

15. The water potential in the Plant
Turgor pressure
Water potential
Y = Ys + Yp

16. Pressure chamber
סכמה
When pressure is applied on a leaf water rises in the petiole.
The water potential is the pressure reading when water are exiting the petiole.
m/watch?v=fpZIdiygy iE
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18. Water potential in Apple tree
SWP-H
SWP-L
LWP-H
LWP-L

19. Water potential and the photosynthesis
When the water potential is decreasing the stomata close
Then the photosynthesis stop
Thus the water potential in the plant affect the photosynthesis