Plant Water Status

7/30/2019 Plant Water Status

1/36

Deficit Irrigation forMediterraneanAgricultural Systems

DIMAS

METHODOLOGY WORKSHOP

IAS-UCO, Crdoba-Spain, 9-11 February 2005

Plant water status


2/36

Plant water status (PWS)

Indicatorsndicators off PWSWS:

tissue water content

relative water content(RWC)

energy status of the water in the cell

water potential()

basic parameters:

crop canopy temperature

stem diameter

stomatal conductance

sap flow

visible symptoms of water stress

indirect methods:


3/36

Plant water status (PWS)

IncaosncaosooPWPWfoorgorgohnhn

tissue water content

relative water content(RWC)

energy status of the water in the cell

water potential()

basic parameters:

stem diameter

crop canopy temperature

stomatal conductance

sap flow

visible symptoms of water stress

indirect methods:


4/36

Measurement of Plant WaterMeasurement of Plant Water StatusStatus

FW DW

TW DW

WATER CONTENT

=WC(DW basis)FW DW

DW=RWC(DW basis)

WATER POTENTIAL

Water potential is defined as the potential energy per unit mass of water withreference to pure water atzero potential (atmospheric pressure and 20 C),(Campbell, 1977)

Measurement of water potential is probably the most satisfactory singlemeasurement of plant and soil water status (Kramer and Koslowski, 1979)


5/36

Measurement of Plant WaterMeasurement of Plant Water StatusStatus

PLANT WATER POTENTIAL

= = T (

l

s)

rs-l

Water flow through the soil-plant-system:

l = s (T rs-l)

l = o+ p (vacuole)Water stress

WATER POTENTIAL MEASUREMENTS

- Pressure chamber method (Scholander et al., 1965)

Principles (x)


6/36

xylem= leaf =, xylem


7/36

Method of measurement

How to measureHow to measure ??

- leaf water potential

- stem water potential


8/36

Method of measurement

When to measureWhen to measure ??

-predawn water potential

- mid-day water potential

Plant water potential varies

throughout the day

Predawn, usually reflectaverage soil moisture tension

predawn, preferred baseline measurement

Mid-day, reflectsthe tension bythe plant to satisfy the water

demandmid-day, indicate the maximum water potential for the day


9/36

Problems ?

Critical values ofmid-day

AlfalfaAlfalfaCottonCotton

CornCorn

PotatoesPotatoesSoybeanSoybean

SorghumSorghum

SugarbeetSugarbeet

SunflowerSunflower

WheatWheat

1.01.0 1.31.31.21.2 1.51.5

1.21.2 1.31.3

0.80.8 1.01.01.11.1 1.51.5

1.31.3 1.51.5

1.21.2 1.41.4

1.01.0 1.41.4

1.41.4 1.91.9

l (MPa)Crop

http://weather.nmsu.Teaching_Material/soil698/pressure_bomb/


10/36

What to measureWhat to measure ??

(Fereres et al., 1999)

Shackel et al., 1997

stem water potential:

Measure of stress in tree crops

LWP muchmore variable and less hepful


11/36

Leaf - stem water potential

convergence


12/36

shaded leaf water potential vs. stem water potential


13/36


14/36

Stem water potentialStem water potential

((ShackelShackel et al., 1997)et al., 1997)


15/36

C ti it i fContinuous monitoring of t k di ttrunk diameter


16/36

Continuous monitoring ofContinuous monitoring oftrunk diametertrunk diameter

for precise scheduling of irrigationsfor precise scheduling of irrigations

trunk diameter fluctuationstrunk diameter fluctuations


17/36

trunk diameter fluctuationstrunk diameter fluctuations


18/36

Trunk Diameter Fluctuations

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

jun 3

12:00a.6./p.6.

jun 4 0:00

a.6./p.6.

jun 4

12:00a.6./p.6.

jun 5 0:00

a.6./p.6.

jun 5

12:00a.6./p.6.

jun 6 0:00

a.6./p.6.

jun 6

12:00a.6./p.6.

jun 7 0:00

a.6./p.6.

jun 7

12:00a.6./p.6.

jun 8 0:00

a.6./p.6.

TrunkDiameter

Fluctuations(mm)

T1.75

T2.75

1

3

4

2


19/36

Citrus; San Joaquin Valley

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

J un 24 J ul 4 J ul 14 J ul 24 Aug 3 Aug 13 Aug 23

Control

T8

Onset of 25% ETc

J uly 1


20/36

Trunk diameter fluctuationsduring deficit irrigation andafter reirrigation


l f S S


21/36


Values of MDTS, MSWP, MLWP, PLWP,for de deficit irrigation treatment, relative to the control


22/36


23/36

Linear Variable Differential Transducer

(LVDT; Model DF 2.5, Solartron Metrology; UK)

Problems?

t t

t t


24/36

crop canopy temperaturecrop canopy temperature

Water flow through the soil-plant-system: l = s (T rs-l)

l = s+ p (vacuole)

Water stress Change the energybalance, andcanopy

temperature

Difference between leaf an air temperature:

Relatable to leaf water potential

(Infrared Thermometers)


25/36

Method Canopy temperature based

Crop Water Stress Index (CWSI):

Tmax= a ( 1 b )-1

Tminx= a+ (b VPD)

Tmin= f (VPD)

=CWSIT T

min

Tmax Tmin

CWSI =1 (T /Tmax)

How to measureHow to measure ??


26/36

stomatal conductancestomatal conductance


27/36

stomatal conductancestomatal conductance

Water flow through the soil-plant-system: l = s (T rs-l)

l = s+ p (vacuole)

Water stress stomatal closureg=1/r)g=1/r)

(g=1/r)

Degree of stomatal opening:

indicative of plant water status

(Porometers)


28/36

system Delta T AP4(DeltaT devices LTD, Cambrige, England)

CIRAS-1 (PP Systems Hitchin HertsU.K.)

Problems ?


29/36


30/36

PROBLEMS


31/36

Diurnal evolution of leaf conductancein almond trees

0 6 8 10 12 14 16

Hour of day

Irrigatedunirrigated8

6

gl

(mm

s-1)

4

2

0

(Castel and Fereres, 1982)

Stomatal conductance and leaf water potential on spring in


32/36

irrigated and rainfed peaches. Winters, California, 1980

(Fereres and Goldhamer, 1990)

STOM

ATALCOND

UCTANCE

(mms-1)

LEAFWATE

R

POTENTIAL

(MPa)

Daily course of Pn, LWP and SC


33/36

Drip-irrigated olive orchard,

cv. Picual

(Gimnez et al., 1997)

Relationship in sunflower between leaf expansion rated l f i l


34/36

and leaf water potential

-1.5 -1.0 -0.5

-0.0

-0.4

-0.8

-1.2

Leaf Water Potential (MPa)

LER(d

ry/we

t)

Exp. 1Exp. 2

y = 1.74 + 1.13 x

r2 = 0.80 ***

(V.O. Sadras, F.J . Villalobos, and E. Fereres, 1993)


35/36

Leaf expansion rateLeaf expansion rate


36/36

Plant Water Status

Documents

Transcript of Plant Water Status