How do plants take
up water in a drying
climate
Prof. Dr. Ulrich Zimmermann
ZIM Plant Technology GmbH
Hennigsdorf near Berlin, Germany
1
Water ascent in trees
The problem of water lifting in tall trees under drought is equivalent to
the problem of water uptake against osmotic pressure
Mangrove, Australia
Sequoia trees, California
(up to 110m tall)
2
Cohesion Theory
• Continuous water columns from the roots to the foliage
• Driving force: negative pressure gradients generated by transpiration
• Negative pressures of up to -15 MPa
Note that water under
negative pressure is in
a metastable state
3
Evidence for hydrophobic xylem walls
Osmiophilic (lipid) lining of
the inner xylem walls of a
resurrection plant (a) and
birch (b).
Rise heights of water (blue)
and benzene (grey)
4
T1 -weighted 1H NMR image of a well hydrated leaf in
dependency of pressure
Spin-density
5
Variation of balancing pressure with height measured on
leafy twigs of a 32-m-tall Eucalyptus pilularis tree
30
r.h.
r.h.
T
T
0.86 ± 0.28
n
T
0.31 ± 0.18
4
2
0
3
0.35 ± 0.18
2
1
0.5
1.0
1.5
0.29 ± 0.18
6
4
2
1
0
0
6
0
0.0
0.62 ± 0.23
4
3
2
0
4
3
2
1
0
4
3
2
1
0
0.0
0.42 ± 0.20
8
6
4
2
0
0.19 ± 0.09
0.40 ± 0.15
9
0.28 ± 0.15
6
3
0.5
1.0
1.5
0
0.0
0.5
1.0
1.5
Pb [MPa]
30
25
T
20
r.h.
r.h.
r.h.
r.h.
T
T
T
15
10:00 11:00 12:00 13:00 13:30 14:30 15:30 16:30 11:30 12:30 13:30 14:30 04:30 05:30 06:30 07:30
time [h] (EST)
February 27th
February 28th
100
90
80
70
60
Relative humidity [%]
Temperature [°C]
0.30 ± 0.10
2
0
0.58 ± 0.18
4
3
2
1
0
4 1.11 ± 0.22
3
2
1
0
0.0
0.5
1.0
1.5
100
90
80
70
60
r.h.
8
6
4
1
ground
level
04:30 05:30 06:30 07:30
15
2
6m
11:30 12:30 13:30 14:30
r.h.
25
20
(d)
T
3
16 m
(c)
10:00 11:00 12:00 13:00 13:30 14:30 15:30 16:30
4
28 m
(b)
Relative humidity [%]
canopy
level
Temperature [°C]
(a)
March 1st
Australia, 2006
6
Balancing pressures measurements on E. pilularis
Apical leafy twigs were taken from a 60m tall E.pilularis at 57m height and in
parallel on the ground
Australia, 2006
7
Plot of balancing pressures measured on twigs of P. nigra
and Eucalyptus pilularis versus relative humidity
Populus nigra
Eucalyptus pilularis
2.5
2.5
2.0
1-5m
5-15m
15-25m
0.0
100
80
60
40
100
80
Relative humidity [%]
60
n=16
n=23
0.5
40
0.0
100
80
60
40
20 100
80
n=72
n=19
1.0
n=18
Pb [MPa]
n=10
1.5
n=50
n=22
n=17
n=16
n=48
n=15
1-5 m
5-15 m
15-25 m
25-35 m
57 m
0.5
n=10
1.0
n=11
n=58
1.5
n=86
n=22
Pb [MPa]
2.0
60
40
20
Relative humidity [%]
Balancing pressures depend on relative humidity, but not on height
8
Pattern of the amount of cohesive water and mobile water
under rapidly changing weather conditions in E. pilularis
cohesive water per cm3 wood
x, embolised
x, liquid
x, embolised
x, liquid
x, liquid
branch pieces before compression
x, liquid
Jet discharge
1.7
1.4
1.4
2.0
2.0
2.3
1.8
5.32.8
3.3
3.8
xylem
sap
CW b,v [µl cm-3 ]
embolised
gas
embolised
5.8
50.0
branch pieces after decompression
5.5
2.2
6.5
4.88.5
9.0
37.5
5.0
2.7
1.3
2.1
1.9
1.52.0
2.3
2.2
2.7
6.5
2.9
7.7
3.0
4.8
7.8
7.0
6.3
*
7.5
2.5
2.2
2.21.6
1.3
2.7
3.0
3.4
4.0
2.42.4
3.0
1.4
3.23.6
2.2
2.34.9
4.7
8.14.9
9.6
25.0
* 9.5
10.0
5.3
12.5
0.0
9.5
8.4
6.0
mobile water per cm3 wood
spin density image
reference
capillary
550.0
MW b,v [µl cm-3]
NMR
2.8
2.0
3.3
2.0
2.0
3.0
1.9 3.6
1.6
4.2
2.3
1.5 3.8 2.1
3.4
2.3
1.8
2.7
437.5
325.0
212.5
100.0
9
Pattern of the amount of CW, MW, and XW per cm3 of
branches of a 32 m tall E. pilularis tree under very rapidly
changing weather conditions
Australia, 2006
10
Re-hydration of twigs by water uptake via leaves and/or bark
as measured by NMR microscopy
Eucalyptus pilularis
dried
refilled under
vacuum
Pb > 3.60 MPa
b
x
p
phe
phi
base-watered
head-watered
Pb = 1.04 ± 0.19 MPa
Pb = 1.13 ± 0.32 MPa
Pb = 0.20 ± 0.04 MPa
Pb = 0.16 ± 0.01 MPa
18 h
27 h
26
11
Cohesive water distribution pattern with height
measured on birches
Germany 2007
12
Salt-tolerance due to mucopolysaccharides
1H
Astronium
fraxinifolium
NMR-images of salt-tolerant Chaco trees
>9m
9m
7m
5m
2m
Zimmermann et al. (2002), Trees 16: 100-111.
2m
Bulnesia
sarmientoi
13
Schematic diagrams of the cell turgor pressure probe and the xylem pressure probe Abbreviations: c = cell, Pc* =cell turgor (= Pc − Pam), Mc = microcapillary, Pt =
pressure transducer, Mr = metal rod, Ms = micrometer screw, x = xylem vessel,
Px = xylem pressure
14
Transpiration
Xylem pressure
Transpiration [mmol m-2 s-1]
Xylem pressure [MPa]
Oscillation of xylem pressure measured in wheat roots
15
Oscillation of turgor pressure measured on cortical cells of
wheat
Turgor pressure (M Pa)
0.55
0.50
0.45
0.40
0.35
0.30
15
30
45
60
75
90
105
120
Time (min)
16
Xylem and cell turgor probe measurements on liana
Xylem pressure (bar)
Turgor pressure (bar)
Time of day
Salzburg, Austria
17
Xylem pressure in dependency on drought
tobacco
cucumber
18
Relationship between the xylem pressure and the water
potential of the cells
Assuming local equilibrium (water exchange time between xylem and
tissue cells: a few seconds)
Px = Pc – πc
Development of pressure in the xylem cannot be considered separately
from the tissue cells
(Renner 1915):
Pc = 0
cavitation
19
Our understanding of nature
will change with
progress of technology
Max Planck
20
What is the Scholander pressure chamber measuring?
Evidence arrived from the non-invasive,
online measuring leaf patch clamp pressure probe
21
The leaf patch clamp pressure probe
The turgor pressure (Pc) in the leaf patch is
opposed to the magnetic pressure (Pclamp). The
ZIM-probe measures the difference (Pp) between
magnetic pressure and turgor.
22
Relationship between patch pressure and turgor pressure
1
⎛ b ⎞a
⎜
⎟
P =
⋅F ⋅P
p ⎜ aP + b ⎟
a clamp
⎝ c
⎠
¾
¾
¾
¾
Pp = patch pressure
Pc = turgor pressure
Pclamp = clamp pressure
Fa = attenuation factor (compression of cuticle, cell walls and air-filled
interspaces)
¾ a, b = elasticity constants
23
Calibration of the leaf patch clamp pressure probe (Pp)
against the leaf cell turgor pressure probe (Pc)
The turgor pressure probe
90
50
80
pressure transducer
Pp [kPa]
cell sap
70
probe 2
30
60
Pp [kPa]
40
silicone oil
50
probe 1
20
40
glass capillary
cells
volume
displacement rod
0
30
100 200 300 400 500
Pc [kPa]
24
Diurnal Pp changes measured on grapevine leaves
a: sun-exposed leaf
b: shaded leaf
c: temperature and relative humidity
25
Stomatal aperture oscillations are reflected in
leaf patch pressure (Pp) oscillations
olive
banana
Pp = oscillation period about 20 min
26
Typical multiple leaf patch clamp probe recordings
on a 4-m tall avocado tree in Australia
red = east
blue = north
grey = south
black = west
Arrows mark temporary sun-exposure
27
Diurnal Pp curves, stem water deficit and soil water content
measured on oak trees
left: well-watered
right: drought
28
Time delay of the maximum in LPCP-Probe readings and the
minimum in dendrometer readings of the diurnal changes
100
80
20
60
10
40
30
Counts
30
20
10
60
50
Pp [kPa]
control
40
1000
500
0
RH [%]
Ta [°C]
SR [W/m²]
50
0
-03:00
00:00
03:00
06:00
09:00
12:00
15:00
Time delay [hh:mm]
40
30
50
drought
40
01/02 Jun 2009
450
30
Counts
Dendrometer [µm]
465
435
20
420
03
05
08
10
13
16
18
21
00
02
10
Time [hh]
0
-03:00
00:00
03:00
06:00
09:00
12:00
15:00
Time delay [hh:mm]
29
Diurnal changes in patch pressure (Pp) and
balancing pressure (Pb) values of well irrigated plants
Pb: north-directed leafs (n = 5 per data-point)
Pp: east-directed leaf
Negev, Israel
30
Plot of Pp (triangles) and Pb (circles) values versus the turgor
pressure values, Pc, measured at the same time of the day by
using the cell turgor pressure probe
60
2.0
1.5
50
1.0
45
40
35
Pb [MPa] Ο
Pp [kPa] ♦
55
The turgor pressure probe
0.5
0
100
200
300
400
500
silicone oil
600
cell sap
Pc [kPa]
pressure transducer
The data could be fitted by the transfer function
(Fa = 0.3, Pclamp = 252 kPa, a = 6.8, b = 49.9 kPa;
r2 = 0.93)
glass capillary
cells
volume
displacement rod
31
The role of mucilage in long-distance water transport and
Foliar moisture uptake from the atmosphere
⎛ ax ,h ⎞
⎟
− M w gh = Vw (Px ,h − Px ,h =0 ) + RT ln ⎜⎜
⎟
a
⎝ x ,h = 0 ⎠
32
Presence of mucilaginous substances in fully functioning
xylem vessels evidenced by alcian blue staining
light microscopy
Rhizophora
mangle
Astronium
fraxinifolium
Salix
fragilis
Rhizophora mangle
Astronium fraxinifolium
cryo-scanning electron microscopy
extracted xylem sap
5 µm
Mucopolysaccharides lower the activity of water. MPS gradients can balance the
weight of a water column at constant pressure.
Zimmermann et al. (2002), Trees 16: 100-111,
Zimmermann et al. (2004), New Phytologist 162: 575-615 (Tansley Review).
33
Kosteletzkya virginica
Mucilage –Alcian Blue precipitates
in the xylem
Applications:
1. Agricultural use of salt-affected tidelands
2. Biodiesel production (18 % seed oil content)
3. Good protein fodder for animals after oil extraction (26 %)
4. Landscape beautification for tideland (long flowering time)
34
Evidence for acid mucopolysaccharides located at the leaf
surface and subsurface
Eucryphia
cordifolia
Astronium
fraxinifolium
20 µm
Nothofagus dombeyi
10 µm
10 µm
Populus
nigra
Bulnesia sarmientoi
20 µm
Eucalyptus pilularis
10 µm
10 µm
Moisture uptake by leaves from the atmosphere is apparently extremely facilitated
by mucilage layers on the leaf surface and by epistomatal mucilage plugs.
35
Mucilage containing epistomatal plugs and LPCP probes
measurements
grapevine without e.p.
grapevine with e.p.
36
Distribution of epistomatal mucilage plugs
37
Resurrection plant Myrothamnus flabellifolia
dry
well - hydrated
38
Lipid bodies induce Marangoni (interfacial) streaming
light microscopy
transmission electron microscopy
The xylem is a full
operating microsystem
Interface induced water flow
Surface tension
lipid bodies (=
)
39
Water ascent by Marangoni streaming
mf = Maragoni flow
cf = counter flow
40
Summary: The Multi-force Theory
of water ascent in trees
Pressure
gradients
20
tree D
18
Height [m]
16
14
tree E
4
1m
5m
0
-1
-2
3
9.5 m
3
ΔP x
22
Xylem pressure (bar)
1
1m
2
1
0
0
12
1
1
ΔP
2
3
0
c
10
22:00
8
6
02:00
2
Turgor pressure (bar )
Xylem
osmotic
gradients
Moisture uptake
from the atmosphere
06:00
10:00
Time of the day
14:00
4
2
0
0
20 40 60 80 100 120 140 160 180 200 220 240
-1
Osmolality [mosmol kg ]
Cellular osmotic
pressure gradients
Mycorrhizamediated
water lifting
Mucilagemediated water
lifting
Capillary
forces
Marangoni
streaming
41
Acknowledgements
ZIM-Plant-Technolog
Dipl. biol. Simon Rüger
Dipl. biol. Wilhelm Ehrenberger
Dipl. biol. Christina Sann
Dipl. biol. Gertraud Zimmermann
Dipl. ing. Ronald Fitzke
Dipl. biol. Rebecca Bitter
42
Thank you very
much for your
attention
43
Simultaneous MRI measurements of flow velocity in the
xylem and the phloem
44
Comparative measurements of leaf water status
grapefruit
leaf patch clamp pressure probe (Pp)
oak
pressure bomb (Pb)
and cell turgor pressure probe (Pc)
were used.
Eucalyptus
Measurements at early spring; inset:
measurements at autumn
45
Time difference between Pp peaking and minimum trunk
diameter: measurements on oak trees subjected to drought
46