Download PSY1 Leaf Psychrometer on Wheat

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PSY1 Leaf Psychrometer
Water movement in plants

Natural systems move matter across
gradients:
• Solutes (Concentration)
• Height
• Pressure

Plants move water across a water
potential gradient (Ψ)
Water moves from
high (soils) to
low (leaves)
water potential
What is water potential (Ψ)?

Integrated measurement of plant response to the environment

Consider it to be equivalent to the blood pressure of a plant
Humidity
Temperature
Soil moisture
Ψ
Solar radiation
Soil nutrients
What is water potential (Ψ)?
Total plant water potential is defined as:
Ψ = Ψp + Ψs + Ψm + Ψg
Ψp = Turgor Pressure
Ψs = Osmotic Potential
Ψm = Matric Potential
Ψg= Gravity Potential
To measure plant water potential...
Pressure chamber (bomb)
In situ Psychrometers
In Situ Psychrometer vs. Pressure chamber?
In Situ Psychrometer
Pressure chamber
Dixon et al, (1984)
Strong relationship between two instruments
Pressure chamber
After correction for
sample temperature
In Situ Psychrometer
Dixon et al, (1984)
PSY1 Leaf Psychrometer
PSY1 Data Logger

Standalone data logging system

High precision 24-bit ADC circuit

Internal micro SD card storage up to 64 GB
Wireless (RF signal) and USB capabilities
up to 250 line of sight


Dynamic smart charging circuit using solar panels
or DC power

Rugged and water proof enclosure for all
external environment conditions
PSY1 Data Logger

Wireless communication

High temporal data collection
(every 10 minutes)

In Situ plant water potential measurements
(leaf and stem)
Stem Psychrometer
Leaf Psychrometer
Leaf Psychrometer Applications
Leaf psychrometers have been tested on
Capsicum
Poplar
Wheat
Corn
Leaf Psychrometer Installation
1. Select flat leaf surface for leaf psychrometer
2. Position leaf into the slot of the clamp
400 600 800
3. Select sandpaper grit based on
thickness of leaf cuticle
4. Apply water on cuticle remover for lubrication
Leaf Psychrometer Installation
5. Abrade surface of leaf in a circular motion
6. Apply silicon grease around psychrometersurface
0.5 mm
7. Spread silicon evenly on psychrometer
surface perimeter (Approx. 0.5mm deep)
8. Insert psychrometer chamber into clamp,
Secure by twisting the chamber on the leaf
Why do you need to abrade leaf surface?

Water vapour on the leaf diffuses through
the substomatal cavity

The cuticle layer varies across different plant
species:
 Cuticle resistance effects the water
potential measurement

Leaf abrasion reduces cuticle resistance and
improves water vapour diffusion in leaf

Leaf abrasion reduces equilibration time of
leaf and psychrometer chamber
Grit Selection
Plant Examples
Grit Selection
Cuticle Size
Citrus
Grasses
Beans
400 Grit
600
800 Grit
Thick Cuticle
Thin Cuticle
Level of Abrasion
Heavy Abrasion
Light Abrasion
No Abrasion
Wheat Application
Wheat Application

Wheat plants (4-weeks old) were grown
in soil media

Leaf psychrometers were installed on five
leaves:
•
Wheat leaf 1/leaf 2 were
adjacent leaves
•
Wheat leaf 3/leaf 4 were
adjacent leaves
•
Control leaf had no abrasion
treatment

All wheat plants were irrigated together
Leaf 4
Control leaf
Leaf 2
Leaf 3
Leaf 1
Wheat Data
Uninstallation of Leaf Psychrometer
Leaf 1 (-3.94 MPa*)
Installation duration: 5 days
Leaf 2 (-1.23 MPa)
Leaf 3 (-1.73 MPa)
Installation duration: 7.5 days Installation duration: 7.5 days
Leaf 4 (-0.90 MPa)
Installation time: 7.5 days
• Leaf 1 – Installation showed signs of failure after 4.5 days
• Leaf 2 – Measurements continued to show reliable leaf water status after a week
• Leaf 3 – Installation showed signs of failure after 4.5 days
• Leaf 4 – Measurements continued to show reliable leaf water status after a week
Wheat Data
All psychrometers exhibited immediate response to
irrigation, indicating installations are still reliable
Wheat Data
Leaf 2 and Leaf 4 still exhibit immediate response to
irrigation. Installations are still reliable
Leaf 1 and Leaf 3 showed no night time
recovery and failed to respond to irrigation
Corn Application
Corn Application

Three potted corn plants grown in a
growth chamber for 4-weeks

Each leaf used 600-grit sand paper to
abrade the cuticle layer

Two leaf psychrometers were installed
per plant at different leaf heights
(Top and Bottom)
Corn 2
Corn 1
Corn 3
Corn Application

Three potted corn plants grown in
growth chamber for 4-weeks

Each leaf used 600-grit sand paper to
abrade the cuticle layer

Two leaf psychrometers were installed
per plant at different leaf heights
(Top and Bottom)
Top Leaf
Corn 2
Corn 3
Bottom Leaf
Bottom Leaf
Corn 1
Top Leaf
Corn Data
Corn Data
After a week of no irrigation, the soil looked dry.
Soil Inspection After a Week of No Irrigation
Before Irrigation
After Irrigation
Corn Data
Plant water status indicates installations were
still reliable after immediate response to irrigation
Wheat and Corn Application Conclusions

Reliable measurements from leaf psychrometer
installations varied between species of plant:
1. Wheat leaves provided up to a week
2. Corn leaves may provide up to two weeks

Abrasion of leaf is required to provide reliable leaf
water status measurements

Installation duration is dependent on a systematic
abrasion technique

Reliable measurements are determined based on
response to night time recovery and/or irrigation
Wheat
Corn
Rice Genotyping Example
Rice genotyping with leaf water potential (LWP)

Study conducted by Sibounheuang et al. (2006)
demonstrated variations in LWP in 6 different rice
genotypes using pressure chambers
Objective of experiment:
A.
Determine genotype variations by measuring
LWP at different leaf positions and plant sizes
B.
Examine whether genotype variations of
different canopy size and water conductance
are associated with LWP
Experiment A




Glasshouse experiment with automated
temperature control system
Six rice lines were tested and have known
differences in LWP, osmotic potential, and
osmotic adjustment from Jongdee (1998)
Midday water potential was measured with
pressure chamber at 4 positions: Tip, Sheath,
Base, Stem during 10 day stress period
Plant size were determined by xylem anatomy
(vascular bundles and stem cross section area)
Experiment A Results



Genotype differences in midday
LWP could be based on hydraulic
conductance
Leaf water potential was
different among the 6 genotypes
and demonstrated the same
trend
Leaf water potential and xylem
area relationship showed
genotypes with higher LWP
showed larger xylem area
Figure 3 from Sibounheuang (2006)
B. Canopy size of genotypes associated with LWP




Field experiment with rainout shelters to induce
stress period of four rice lines
Midday LWP was measured under 3 irrigation
treatments (Irrigated, 14 and 18 days of stress) and
4 canopy sizes (control, 1/3 and 2/3 leaf removal
and six tillers remaining)
Midday water potential was measured at 4, 10 and
14 days after imposed stress
Canopy size was measured by the number of
vascular bundles
Experiment B results



Genotype variations of reduced canopy sizes
(removing leaves/tillers) were not significantly
reflected in LWP
Differences in LWP among genotype variations
were were not due to canopy size
Leaf water potential expressed in different
genotypes maintained the same trends, however
differences were not due to canopy size or leaf
area
Figure 5 from Sibounheuang et a. (2006)
Sibounheuang et a. (2006) Conclusions



Genotype variation expressed in LWP and change in water stress were largely
seen at leaf tip.
Larger xylem size were associated with high LWP demonstrating a higher
internal water conductance
Hydraulic conductance of vascular bundles could have caused the genotype
variation seen in rice.
Leaf Psychrometer Conclusions



PSY1 data logging systems provide wireless, continuous and automated
measurements with a wide range of applications
Leaf psychrometers demonstrated reliable plant water status for
wheat and corn crops up to a week of continuous measurements
Plant water status of rice crops have previously been monitored by the
pressure chamber technique for genotyping. Leaf psychrometers provides the
opportunity to continuously monitor leaf water status of rice in real time
Postal: PO Box 503, Armidale, NSW 2350 Australia
Address: 211 Mann St, Armidale, NSW, 2350 Australia
Email: [email protected] Phone: +61 2 6772 6770