DIFFERENT STRATEGIES FOR WATER AVAILABILITY IN FOUR MEDITERRANEAN SCLEROPHYLLOUS PLANTS Ceratonia si

1
DIFFERENT STRATEGIES FOR WATER AVAILABILITY IN
FOUR MEDITERRANEAN SCLEROPHYLLOUS PLANTS
(Ceratonia siliqua, Olea oleaster, Pistacia
terebinthus and Quercus coccifera) GROWING ON
HEALTHY AND DEGRADED AREA

• Prepared by
• Dr. M. Serdal SAKÇALI

The present study was funded by EU in the frame
of the project entitled "Desertification in
Mediterranean Drylands Development of a
monitoring System based on Plant Ecophysiology
(DEMOS, Contract no IC18-CT97-0153).
2
Environmental Problems

• pollution
• poor management
• population pressure
• degradation
• desertification,
• global warming,
• ozone depletion,
• climatic changes, excessive erosion, decreasing
  biodiversity, melting of glaciers, ..

3
Water and Plants

• Plants are typically about 90 water.
• A typical crop or grassland will transpire about
  500 kg of water per kg dry wt. produced.
• Water transports inorganic nutrients and
  photosynthetic products to various parts of the
  plant.
• Water is also the electron donor for
  photosynthesis.
• Water evapotranspiration also keeps plants from
  overheating.

4
Movement Direction of Water in Plant
5
Transpiration

• Stomatal pores in leaves open to allow movement
  of carbon dioxide in leaf for photosynthesis
• Water vapor is lost through pores by
  transpiration
• Loss of water from non pore areas is restricted
  by a waxy impermeable cuticle

6
Transpiration of Some Plants
7
Stomatal control

• When water stressed, plants increase thickness of
  cuticle
• In light, guard cells accumulate potassium ions
  and organic acids
• This decreases their osmotic pressure which
  causes them to fill with water and enlarge the
  stomatal pores
• Extra water losses will cause the cells and pores
  to shrink, reducing water loss
• Under conditions of water stress, leaves produce
  a hormone, abscisic acid, which promotes stomata
  closure
• Stomatal pore size can also be regulated by CO2
  concentration

8
Stomatal Opening
Conditions favouring Conditions
favouring closing
opening Lack of water
Abundant water Darkness
Abundant Light
High internal CO2 Low internal
CO2 Presence of ABA High
humidity
9
Absorption

• Absorption refers to uptake of water by roots to
  compensate for water losses by transpiration
• During daylight, transpiration exceeds absorption
  and cells shrink lowering their water potential
• At night, stomatal pores close and water
  potential of leaves becomes restored.

10
Water Potential

• The movement of water in osmosis involves both
  diffusion and mass flow
• The free energy gradient of water
• chemical potential of water
• The major components of water potential are
  turgor pressure and osmotic potential

11
(No Transcript)
12
? ?P?pqgh ?P Turgor
pressure ?p
Osmotic potential
qDensity gGravity
hAltitude

• ?P The pressure of water pushing against the
  inside of the cell wall
• ?p -CRT
• C Molar concentration of solute
  (moles/L)
• R Gas constant (8.31 m3 Pa mole K-1)
• T Temperature (0K)
• ?p of Sea water 2.49 Mpa
• Plant cell sap 0.73 MPa

13
Summary of Factors Influencing water potential