How do plants take How do plants take up water in a drying up water in a drying climate 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
T 1 -weighted 1 H 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 (a) (b) (c) (d) Relative humidity [%] 10:00 11:00 12:00 13:00 13:30 14:30 15:30 16:30 04:30 05:30 06:30 07:30 11:30 12:30 13:30 14:30 Temperature [°C] 100 30 canopy r.h. T r.h. r.h. 90 25 level 80 20 T 70 r.h. T T 60 15 8 4 6 0.62 ± 0.23 0.30 ± 0.10 4 0.86 ± 0.28 0.29 ± 0.18 6 3 3 4 4 28 m 2 2 2 2 1 1 0 0 0 0 6 8 0.58 ± 0.18 0.31 ± 0.18 4 0.42 ± 0.20 0.19 ± 0.09 4 6 3 3 4 16 m n 2 4 2 2 2 1 1 0 0 0 0 1.11 ± 0.22 3 4 0.35 ± 0.18 0.40 ± 0.15 0.28 ± 0.15 4 9 3 3 2 6 6 m 2 2 1 3 1 1 0 0 0 0 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 P b [MPa] Relative humidity [%] Temperature [°C] 100 30 r.h. r.h. r.h. 90 T ground 25 80 level r.h. T 70 20 T T 60 15 13:30 14:30 15:30 16:30 11:30 12:30 13:30 14:30 04:30 05:30 06:30 07:30 10:00 11:00 12:00 13:00 time [h] (EST) February 27 th February 28 th March 1 st 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 1-5m 2.5 5-15m 2.0 15-25m 2.0 1.5 P b [MPa] n=16 1.5 P b [MPa] n=23 n=58 n=11 1.0 n=10 1.0 n=22 n=16 n=86 n=10 n=19 n=17 n=72 n=15 n=22 n=48 n=50 1-5 m 0.5 0.5 5-15 m n=18 15-25 m 25-35 m 57 m 0.0 0.0 100 80 60 40 100 80 60 40 100 80 60 40 20 100 80 60 40 20 Relative humidity [%] 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 cm 3 wood cohesive water per cm 3 wood Jet discharge branch pieces before compression branch pieces before compression 1.8 1.8 x, embolised x, embolised x, embolised x, embolised 1.7 1.7 1.4 1.4 2.7 2.7 1.4 1.4 2.0 2.0 2.8 2.8 5.0 5.0 x, liquid x, liquid x, liquid x, liquid x, liquid x, liquid x, liquid x, liquid 2.0 2.0 2.0 2.0 2.3 2.3 3.3 3.3 2.0 2.0 2.7 2.7 1.3 1.3 2.0 2.0 1.8 1.8 3.0 3.0 2.8 2.8 2.1 2.1 5.3 5.3 1.9 1.9 3.6 3.6 1.9 1.9 1.6 1.6 1.5 1.5 2.2 2.2 2.0 2.0 3.3 3.3 4.2 4.2 1.6 1.6 2.4 2.4 2.2 2.2 2.4 2.4 2.3 2.3 2.3 2.3 2.2 2.2 2.5 2.5 1.3 1.3 3.8 3.8 1.5 1.5 6.5 6.5 2.1 2.1 2.7 2.7 3.0 3.0 3.8 3.8 2.7 2.7 3.4 3.4 2.9 2.9 1.4 1.4 7.7 7.7 3.0 3.0 3.0 3.0 5.5 5.5 3.6 3.6 2.3 2.3 2.2 2.2 3.2 3.2 4.8 4.8 7.8 7.8 6.5 6.5 2.2 2.2 5.8 5.8 4.9 4.9 7.0 7.0 2.3 2.3 3.4 3.4 6.3 6.3 4.8 4.8 * * 4.7 4.7 8.5 8.5 4.0 4.0 7.5 7.5 50.0 50.0 embolised embolised embolised embolised 9.0 9.0 gas gas -3 ] -3 ] 37.5 37.5 8.1 8.1 4.9 4.9 CW b,v [µl cm CW b,v [µl cm 9.6 9.6 * * 9.5 9.5 25.0 25.0 xylem xylem 10.0 10.0 sap sap 5.3 5.3 12.5 12.5 branch pieces after decompression branch pieces after decompression 9.5 9.5 6.0 6.0 8.4 8.4 0.0 0.0 mobile water per cm 3 wood mobile water per cm 3 wood spin density image NMR reference capillary 550.0 550.0 MW b,v [µl cm -3 ] MW b,v [µl cm -3 ] 437.5 437.5 325.0 325.0 212.5 212.5 9 100.0 100.0
Pattern of the amount of CW, MW, and XW per cm 3 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 dried refilled under refilled under vacuum vacuum P b > 3.60 MPa P b > 3.60 MPa b x p ph e ph i base-watered base-watered head-watered head-watered P b = 1.04 ± 0.19 MPa P b = 1.04 ± 0.19 MPa P b = 1.13 ± 0.32 MPa P b = 1.13 ± 0.32 MPa 18 h 18 h P b = 0.20 ± 0.04 MPa P b = 0.20 ± 0.04 MPa P b = 0.16 ± 0.01 MPa P b = 0.16 ± 0.01 MPa 27 h 27 h 26 26 11
Cohesive water distribution pattern with height measured on birches Germany 2007 12
Salt-tolerance due to mucopolysaccharides 1 H NMR-images of salt-tolerant Chaco trees > 9 m 9 m 5 m 7 m Astronium Bulnesia 2 m fraxinifolium 2 m sarmientoi Zimmermann et al. (2002), Trees 16: 100-111. 13
Schematic diagrams of the cell turgor pressure probe and the xylem pressure probe Abbreviations: c = cell, P c * =cell turgor (= P c − P am ), Mc = microcapillary, Pt = pressure transducer, Mr = metal rod, Ms = micrometer screw, x = xylem vessel, P x = xylem pressure 14
Oscillation of xylem pressure measured in wheat roots Transpiration [mmol m -2 s -1 ] Transpiration Xylem pressure [MPa] Xylem pressure 15
Oscillation of turgor pressure measured on cortical cells of wheat 0.55 Turgor pressure (MPa) 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 Turgor pressure (bar) Xylem 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) P x = P c – π c Development of pressure in the xylem cannot be considered separately from the tissue cells (Renner 1915) : P c = 0 cavitation 19
Our understanding of nature Our understanding of nature will change with will change with progress of technology progress of technology Max Planck 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 (P c ) in the leaf patch is opposed to the magnetic pressure (P clamp ). The ZIM-probe measures the difference (P p ) between magnetic pressure and turgor. 22
Relationship between patch pressure and turgor pressure 1 ⎛ ⎞ a ⎜ ⎟ b = ⋅ ⋅ P F P ⎜ ⎟ + p a clamp aP b ⎝ ⎠ c � P p = patch pressure � P c = turgor pressure � P clamp = clamp pressure � F a = attenuation factor (compression of cuticle, cell walls and air-filled interspaces) � a, b = elasticity constants 23
Calibration of the leaf patch clamp pressure probe (P p ) against the leaf cell turgor pressure probe (P c ) The turgor pressure probe 90 50 80 P p [kPa] 40 70 silicone oil probe 2 cell sap 60 P p [kPa] 30 50 pressure transducer probe 1 20 40 glass capillary 30 0 100 200 300 400 500 cells volume displacement rod P c [kPa] 24
Diurnal P p changes measured on grapevine leaves a: sun-exposed leaf c: temperature and relative humidity b: shaded leaf 25
Stomatal aperture oscillations are reflected in leaf patch pressure (P p ) oscillations olive banana P p = 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 50 control 40 SR [W/m²] 1000 500 0 100 30 30 80 Counts RH [%] T a [°C] 60 20 20 40 10 10 60 50 0 P p [kPa] -03:00 00:00 03:00 06:00 09:00 12:00 15:00 Time delay [hh:mm] 40 30 50 drought 465 40 Dendrometer [µm] 01/02 Jun 2009 450 30 Counts 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 (P p ) and balancing pressure (P b ) values of well irrigated plants P b : north-directed leafs (n = 5 per data-point) P p : east-directed leaf Negev, Israel 30
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