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

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Photosynthesis light reaction

Whitehead & Gower, 2001

The stomata

•:// . . / ? =Http www youtube com watch v IlmgFYmbAUg

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The Stomata

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Stomata structure

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Opening of the Stomata

Controlling factors

Lights

Plant water potential

Environmental conditions:

atmosphere humidity

Co2 concentration

temperature

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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 400-700 nm

Why do plants are green

• Peaks of absorbents 430, 680 nm

• Which light is corresponded to wave length of 550 nm?

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Light

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

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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 stomata2. Transfer of water vapors from the stomata to the atmosphere

• Factors that control the rate of transpiration1. VPD2. Stomata conductance3. Wind speed

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Vapor transferWhat 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.

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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.

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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

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Pressure chamberסכמה

חנקן בלחץ

לחץ תא

גומיה

•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.com/watch?v=fpZIdiygyiE

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Water potential in Apple tree

SWP-H

SWP-L

LWP-H

LWP-L

Water potential and the photosynthesisWhen the water potential is decreasing the stomata closeThen the photosynthesis stopThus the water potential in the plant affect the photosynthesis