"Water in plant (its uptake and distribution)"
Jiye RHEE
jrhee@jcu.prf.cz
KEBR562- Small plant physiology – Chapter : Water in plant
1. Water Balance of Plants
2. Water channel protein (Aquaporin)
KEBR562- Small plant physiology – Chapter :Water in plant
1. Water Balance of Plants
2. Water channel protein (Aquaporin)
- Differences in :
Water vapor concentration
Hydrostatic pressure
Water potential
KEBR562- Small plant physiology – Chapter : Water in plant
- Water moves through soil by BULK FLOW
- ‘ BULK FLOW’
- connected movement of groups of molecules all together,
most often in response to a pressure gradient
- Water absorption from Soil
KEBR562- Small plant physiology – Chapter : Water in plant
Plant roots
KEBR562- Small plant physiology – Chapter : Water in plant
- Water uptake in the roots
1. Apoplast pathway : water moves through cell walls without crossing any membranes
2. Transmembrane pathway : enter a cell on one side, exists the cell on the other side,
enter next cell , and so on
3. Symplast pathway : via plasmodesmata
- At the endodermis- Casparian Strip
KEBR562- Small plant physiology – Chapter Water in plant
KEBR562- Small plant physiology – Chapter : Water in plant
KEBR562- Small plant physiology – Chapter : Water in plant
Water transport through xylem
- consist of two types of tracheary elements
Tracheids
Vessile elements
KEBR562- Small plant physiology – Chapter : Water in plant
Water transport through xylem
- Plants can get embolism tool
- Air bubbles can form in xylem
- Cavitation
KEBR562- Small plant physiology – Chapter : Water in plant
Venation of a tobacco leaf
- The tensions needed to pull water through
the xylem are the result of evaporation of
water from leaves
KEBR562- Small plant physiology – Chapter : Water in plant
Water evaporation in the leaf
affect the xylem
Tension or negative pressures originate
in leaves
Transpiration pull
As the radius of curvature decreases, the pressure decreases
(become more negative)
KEBR562- Small plant physiology – Chapter : Water in plant
Water pathway through the leaf
KEBR562- Small plant physiology – Chapter : Water in plant
Water vapor diffuse quickly in air
Transpiration from the leaf depends on two factors:
- One, Difference in water vapor concentration between leaf air paces and the
atmosphere
- Two, The diffusional resistance of the pathway from leaf to atmosphere
Two components:
- Leaf stomatal resistance
- Boundary layer resistance
KEBR562- Small plant physiology – Chapter : Water in plant
Boundary layer resistance
- Still air
- Windy conditions
KEBR562- Small plant physiology – Chapter : Water in plant
Stomatal control
Remember the way cuticle?
- Regulate water loss in plants and the
rate of CO2 uptake
OPEN/CLOSED
KEBR562- Small plant physiology – Chapter : Water in plant
Stomatal guard cells
Stomatal resistance can be controlled by opening and closing the stomatal pores.
Specialized cells- The Guard cells
Two main types :
Monocot and grasses – Dumbbell shape, pore is a long slit
Dicot – kidney shape
Q: When water is limited or abundant?
KEBR562- Small plant physiology – Chapter : Water in plant
The radial alignment of the cellulose
microfibrils
(A) a kidney shape stoma
(B) a glasslike stoma
KEBR562- Small plant physiology – Chapter : Water in plant
Representative overview of
water potential and its components
SOIL-PLANT-ATMOSPHERE
continuum
KEBR562- Small plant physiology – Chapter Water in plant
Summary
- Water is the essential medium of life
- Land plants faced with dehydration by water loss to the atmosphere
- There is a conflict between the need for water conservation and the
need for CO2 assimilation
- This determines much of the structure of land plants
1. extensive root system – to get water from soil
2. low resistance path way to get water to leaves – xylem
3. leaf cuticle – reduces evaporation
4. stomata – controls water loss and CO2 uptake
5. guard cells – control stomata
KEBR562- Small plant physiology – Chapter : Water in plant
1. Water Balance of Plants
2. Water channel protein (Aquaporin)
KEBR562- Small plant physiology – Chapter : Water in plant
- Structure
NPA motif, ar/R selectivity filter
- Five main homologous subfamilies :
Plasma membrane Intrinsic Protein (PIP)
Tonoplast Intrinsic Protein (TIP)
Nodulin-26 like Intrinsic Protein (NIP)
Small basic Intrinsic Protein (SIP)
X Intrinsic Protein (SIP)
KEBR562- Small plant physiology – Chapter Water in plant
Cell pressure probe
Meniscus
KEBR562- Small plant physiology – Chapter Water in plant
Function expression of Aquaporin genes Xenopus oocyte
KEBR562- Small plant physiology – Chapter Water in plant
Relative volume
1.30
1.25
H2O
1.20
CuPIP1
FgPIP2
1.15
1.10
1.05
1.00
0.95
0
H2O
FgPIP2
H2O
CuPIP1
30
60
Time (sec)
90
120
KEBR562- Small plant physiology – Chapter Water in plant
Questions
1. Explain, in terms of water potential how water moves from the soil to the
endodermis in a root
2. Explain why, in summer, the diameter of a branch is smaller at noon than
at midnight