Irrigation and Plant Physiology
The basis of irrigation
•
•
•
•
Soil
Plant
Evapotranspiration
Plant requirements
Photosynthesis
• http://www.youtube.com/watch?v=IlmgFYmbAUg
• Exchanges of gases and water
vapors.
• Sugar synthesis
Photosynthesis light reaction
4
Whitehead & Gower, 2001
The stomata
Http://www.youtube.com/watch?v=IlmgFYmbAUg •
The Stomata
6
Stomata structure
7
Opening of the Stomata
Controlling factors
Lights
Plant water potential
Environmental conditions:
atmosphere humidity
Co2 concentration
temperature
8
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 400700 nm
9
Why do plants are green
• Which light is
corresponded to wave
length of 550 nm?
• Peaks of absorbents 430, 680 nm
Light
• It is not possible to have photosynthesis without light,
therefore when there is no light the stomata is closed
11
Transpiration process
• Transpiration is the process of evaporation or vapor transfer from the plant to the
atmosphere through the stomata
• Transpiration has two stages:
1. The vaporization of liquid water in the stomata
2. Transfer of water vapors from the stomata to the atmosphere
• Factors that control the rate of transpiration
1. VPD
2. Stomata conductance
3. Wind speed
12
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.
13
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.
14
The water potential in the Plant
• Turgor pressure
• http://www.youtube.com/watch?v=1ZWP65Nbwd4
• Water potential
• http://www.youtube.com/watch?v=nDZud2g1RVY
Y = Ys + Yp
15
Pressure chamber
‫סכמה‬
‫גומיה‬
‫תא לחץ‬
16
‫חנקן בלחץ‬
• 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.
• http://www.youtube.co
m/watch?v=fpZIdiygy
iE
17
Water potential in Apple tree
SWP-H
SWP-L
LWP-H
LWP-L
18
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