WATER RELATIONS IN THE SOIL-PLANT SYSTEM: WHAT CAN WE ... · 4 WATER FLOW IN THE SOIL-PLANT SYSTEM...
Transcript of WATER RELATIONS IN THE SOIL-PLANT SYSTEM: WHAT CAN WE ... · 4 WATER FLOW IN THE SOIL-PLANT SYSTEM...
WATER RELATIONS IN THE SOIL-PLANT SYSTEM:
!
WHAT CAN WE LEARN FROM FUNCTIONAL-STRUCTURAL
PLANT MODELS
[email protected] @guillaumelobet
Plant PhysiologyULg
Guillaume Lobet PhytoSYSTEMS, University of Liège
SEB Manchester - 04th of July 2014
Illustration: Lore Kutschera
WATER IS CENTRAL IN AGRICULTURE
• Farming accounts for 70% over worldwide water use !
• Global changes reduce water availability
!
• Better water use at the crop level (agricultural practices)
!
• Better water use at the plant level (physiology, genetics)
Photo credit: Viewminder @ Flickr
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WATER FLOW IN THE SOIL-PLANT SYSTEM IS A PASSIVE PROCESS
Plant PhysiologyULg
Air
Leaf
Stem
Root
Soil-0.2
-0.4
-0.5
-0.6
-90
MPa
10%
90%
3 x 10¹⁴ l/year [maize]
Water loss is a passive process, driven by
water potential [ψ] differences in the
system
ψ water potential
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WATER FLOW IS REGULATED AT MULTIPLE SITES
Plant PhysiologyULg
CO2
H2O
Stomata closed
Stomata open
gs stomatal conductance
ActivePassive
ψxyl ψsoil
ψsoil
Kx
Kx
Kr
Krψxyl
ψxyl ψsoil
Kx
Kr
ψxyl ψsoil
KxKr
ψxylψsoil
ψsoil
Kx
Kx
Kr
Krψxyl
ψxylψsoil
Kx
Kr
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WATER FLOW IS REGULATED AT MULTIPLE SITES
Plant PhysiologyULg
10
WATER MOVEMENT IS A COMPLEX PROCESS
Plant PhysiologyULg
Water flow in the SPAC is:
a passive process regulated at multiple sites
active and passive regulation an heterogeneous process in space an heterogeneous process in time
a process occurring at different scales
Systems biology Functional Structural Plant Models
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PLANT AS A CONNECTED NETWORK
Plant PhysiologyULg Lobet et al. 2014. Ecological Modelling
PlaNet-Maize - functional-structural model - 1000’s of connected articles - regulation at the article level - simplified soil
ELECTRICAL ANALOGY
Plant PhysiologyULg Doussan et al., 2006. Plant and Soil
Jh
(z) = �Kx
� x
(z)�z
Axial flux
Jr
(z) = Kr
[ e
(z)� x
(z)]S
Radial flux
Matricial resolution
Landsberg, J. & Fowkes, N., 1978. Annals of Botany
Fluxes
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WATER FLOW REGULATION BY THE PLANT
Plant PhysiologyULg Lobet et al. 2014. Ecological Modelling
0
0.4
-0.5-3.5water potential (MPa)
mod
ifying
fact
or (-
) 1
Axial resistance
rootshoot
0
0.4
-0.5-3.5water potential (MPa)
mod
ifying
fact
or (-
) 1
Radial resistance
root
shoot
cavitation onset / resorption
stomata closing / opening aquaporin gating / trafficking
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SIZE MATTERS. REGULATION AS WELL.
Plant PhysiologyULg
Col
lar w
ater
pot
entia
l [M
Pa]
-6
-4
-2
0A
Root/shoot surface ratio [-]
Col
lar w
ater
pot
entia
l [M
Pa]
*
* ****
*
*
** ******
** ******
** ******
** * *****
** * *****
** * ** ***
Root/shoot surface ratio [-]
No regulation
0 1 2 3 4Root/shoot surface ratio [-]
Col
lar w
ater
pot
entia
l [M
Pa] *
* ***
********
**
** **
***
*
** ****
**** ****** ** * ****
*** * ** ***
cavitation > 90%
B
0 1 2 3 4
Regulation
-6
-4
-2
0
Root system size is important to sustain the shoot evaporative demand
Regulation of hydraulic properties is critical for water homeostasis
Permanent Wilting Point
100 150 200 250 300
-1.0
-0.8
-0.6
-0.4
-0.2
time [h]
wat
er p
oten
tial [
MP
a]
100 150 200 250 300
0.2
0.4
0.6
0.8
1.0
time [h]
gs [-
]
100 150 200 250 300
0.85
0.90
0.95
1.00
time [h]
Kr [
-]
100 150 200 250 300
0.6
0.7
0.8
0.9
1.0
time [h]
Kx
[-]
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ALL REGULATIONS ARE NOT BORN EQUAL
Plant PhysiologyULg
Xylem potential [MPa]
Mod
ifier
1
0
-1.5 0
inhibited
enhanced - gs has a strong effect - Kr has a moderate effect - Kx has almost no effect
- Simultaneous observation - Interactions between regulations
DOES THE SOIL MATTERS?
Plant PhysiologyULg
Soil
Water potential [MPa]
Cond
uctiv
ity [m
/ se
c M
Pa]
10-10
10-20
10-4 10-2 100
100
soil
plant
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cultivated soils
“When the soil is wet it has little influence on the uptake of water
from it by the plant. When it is dry it has a large influence. When it is neither wet nor dry, the extent of
influence is a matter of controversy.”
Passioura, 1980
drying
Systems biology Functional Structural Plant Models
19Plant PhysiologyULg
MODELLING SOIL-PLANT WATER MOUVEMENTR-SWMS
- functional-structural model - 1000’s of connected articles - explicit 3D soil water movement - no shoot (boundary condition)
Javaux et al. 2008. Vadoze Zone Journal
20Plant PhysiologyULg
SOIL PROPERTIES SHAPE THE WATER UPTAKE
Draye et al. 2010. Journal of Experimental Botany
soil water potential (M
Pa)
Clay Clay-loam Loam
- Same root architecture
- Same hydraulic properties
- Different soil types
- Same initial water content
21Plant PhysiologyULg
SOIL WATER CONTENT SHAPES THE WATER UPTAKE
Javaux et al. 2008. Vadoze Zone Journal
Compensatory uptake
22Plant PhysiologyULg
SOIL WATER DISTRIBUTION SHAPES THE WATER UPTAKE
Lobet et al. 2014. Plant Physiology
0
30
-30
0
10
-10
Relative difference
[%]
0.6
1.2
0
0.18
0.24
0.12
Water content [cm3/cm3]
Radial rootwater flow[cm3/day]
Relative difference
[%]
A B
New variables
Uptake sites
Water potentialSoil water content
3D water flow soil-root domain
23Plant PhysiologyULg
USING FSPM TO ANALYSE EXPERIMENTAL DATA
Transpiration
Root system
Soil properties
Soil water contentVALIDATION
R-SWMS
24Plant PhysiologyULg
USING FSPM TO ANALYSE EXPERIMENTAL DATA
30 1.5
WU [cm³/cm³.d]
-0.80 -0.4
ψ [MPa]WC [%]
400 20
New
variables
Time [day]
1
2
3
Plant PhysiologyULg
WATER FLOW IN THE SPAC: WHAT CAN WE LEARN FROM FSPM’S?
FSPM’s are needed to analyse complex systems - sensitivity analysis - counter-intuitive phenomenon
Strong interplay between regulatory element - endogenous - exogenous
Limiting step may vary depending on the scenario
Do not forget the soil!
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QUANTITATIVE DATA ARE MISSING…
Plant PhysiologyULg
Well known, many quantitative data
Very few quantitative data. Cavitation susceptibility curves.
Data only for certain species / root types Data about single roots What about the connections?
Very few quantitative data. Environment responses?
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WHERE DO WE GO NEXT?
Plant PhysiologyULg
Long distance signalling ABA signalling Auxin movement …
Lower scale modelling Radial water movement Lateral root formation ….
Higher scale modelling Integration with crop models ….
ACKNOWLEDGEMENTS
Plant PhysiologyULg
Université catholique de Louvain Xavier Draye Mathieu Javaux Félicien Meunier Vincent Larondelle
UC Davis Valentin Couvreur
INRA Avignon Loïc Pagès Pierre Valsesia
BELSPO Belgian Science Policy
FNRS Fond National de la Recherche Scientifique
All models are wrong but some are useful.
George Box, 1987
Presentation available on figshare
bit.ly/seb-lobet