H d li ti ti t bli h t d ff t fHydraulic activation: establishment and effects of liquid water bridges across the stomata

Jürgen Burkhardt Shyam Pariyar Mauricio HunscheJürgen Burkhardt, Shyam Pariyar, Mauricio Hunsche

Institute of Crop Science and Resource Conservation

University of Bonn, Germany

ESA 100, Baltimore, USA, 12th August, 2015

Research questions

What is the influence of leaf surface particles(deposited aerosols) on the(deposited aerosols) on the

- duration of foliar micro-wetness ?- water surface tension on leaves ?- stomatal liquid water transport ?stomatal liquid water transport ?

Dew chemistry from Scots pine and neighboring Norway spruce

uce

atio ay

spru

atio

nra

e/N

orw

ncen

traot

spi

neC

onS

co

Dew chemistry is governed by deposited aerosols(Burkhardt 1989)

Electrical conductance on spruce needles14 m height

emen

s]relative humidity 100

80

1,4

g

dle

[10-9

sie

%]

e a e u d y

8060

1 0

1,2

pruc

e ne

ed

hum

idity

[%

60

400,8

1,0

atio

n [m

m]

ucta

nce

sp

rela

tive

spruce needleconductance

40

0,4

0,6

prec

ipita

trica

l con

du spruce needle

0

2020

0,2

,

rainfalli it ti

elec

t

CET

0

12 18 0 6 12 18 0 6 12 18 0 60

0,0precipitation

10.8.92 11.8. 12.8. 13.8.CET

(Burkhardt & Eiden, Atm. Env. 1994)

22s]

80

100

dle

[10-9

sie

men

s

%]

relative humidity

20

40

60

nce

spru

ce n

eed

lativ

e hu

mid

ity [%

conductance

18

0

20

ectri

cal c

ondu

cta re

spruce needleconductance

emen

s]

relative humidity 100

80

1,4 11.8.92 12.8.92CET

12 18 0 6 12 18

0

ele

pruc

e ne

edle

[10-9

sie

hum

idity

[%]

60

80

40

60

0,8

1,0

1,2

atio

n [m

m]

trica

l con

duct

ance

sp

rela

tive

spruce needleconductance

0

20

40

20

0,2

0,4

0,6

prec

ipita

rainfalli it ti

elec

t

10.8.92 11.8. 12.8. 13.8.CET

0

12 18 0 6 12 18 0 6 12 18 0 60

0,0precipitation

(Burkhardt & Eiden, Atm. Env. 1994)

90

28ns]80

90

28

men

s]80

26 relative humiditysiem

e70

80

26 relative humidity10

-9 s

iem

60

70

24

ce [1

0-9

y [%

]6024

tanc

e [1

mid

ity [%

]

50

60

22

ucta

nc

e hu

mid

ity

el conductance on spruce needle 40

50

20

22

cond

uct

rela

tive

hum

el. conductance on spruce needle

4020

l con

d

rela

tive el. conductance on spruce needle

30

40

18

ectr

ical

c r

3018

ectr

ica

0 3 6 9 12 15 18 212016

ti [h]

ele

0 3 6 9 12 15 18 212016

ele time [h]

NH3 added

‘ ‘time [h]

(Burkhardt & Eiden, Atm. Env. 1994)

Ammonia dissolves ‘real water‘

Comparison of leafwetness sensorswetness sensors

Potato field, southern Germany,hot summer week

Burkhardt & HunscheHunsche, Frontiers in Plant Science,2013

Foliar micro-wetness

Water vapor from atmospheric humidity and/or fromWater vapor from atmospheric humidity and/or fromtranspiration, condensing to hygroscopic leafsurface particlessurface particles.

Particles act similar to cloud condensation nucleiParticles act similar to cloud condensation nuclei.

turbulent boundary layeraye

laminar boundary layery y

Spruce needle

Substomatal cavity

Deliquescence:Deliquescence:the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solutionwater and forms a solution

Deliquescence humidityDeliquescence humidityDRH (NaCl): 75%DRH (NaClO3): 75%DRH (CaCl2): 32%DRH (NH4HSO4): 40%DRH ((NH ) SO ): 80%DRH DRH ((NH4)2SO4): 80%

66% RH

50 100 %RH75

Stomatal water uptake?

‚NO‘ - Based on - droplets/stomatal geometry- cuticular hydrophobicity

water surface tension- water surface tension- pure water, clean surface

(Schönherr & Bukovac,Plant Phys., 1972)

• Stomatal geometry not relevant for thin films• Hygroscopic particles reduce hydrophobicity• Reduced water surface tension of concentrated solutions (ion

specific)

Franz Hofmeister,physiologistphysiologist1850 - 1922

Arch Exp Pathol Pharmakol. (1888):

(‘lyotropic series‘)

IO3- F-

chaotropic‘structure-breakers‘

kosmotropic‘structure-makers‘

protein solubilityprotein solubilityhydrophobicity

surface tensionsurface tension

Environmental Pollution, 2014, supplementary file

Section of stoma of an onion leaf with salt particle (P) on surfaceGC: guard cell, SW: stomatal wall, SSC: substomatal cavity

Burkhardt, Ecol. Monographs, 2010

CeCl3 auf Zwiebelblatt

Hydraulic activation of stomata (HAS) – bidirectional exchange of water, solutes, information (hydraulic signalling). Burkhardt, Ecol. Monographs, 2010

eCl3 auf Zwiebelblatt

HAS enables second pathway of stomatal transpirationBurkhardt, Ecol. Monographs, 2010

Epidermal minimum conductance (gmin) of Scots pineneedles increases by spraying with salt solutions

1.5

needles increases by spraying with salt solutions

1 0

***

m‐2s‐1) 

1.0

** ****

***

(mmolm

0.5

g min

0.0H2O (NH4)2SO4 NaCl NaCl+ 

surfactantNaNO3 KI (Burkhardt & Pariyar, 

Env Poll 2014)surfactant

High gmin low drought tolerance

Env. Poll., 2014)

Summary and conclusionsF li i t i f d b l f f ti l iFoliar micro-wetness is formed by leaf surface particles, air humidity, and transpiration. May be permanently present.

Fluctuations of relative humidity can cause dynamic particle expansion into the stomata (HAS)expansion into the stomata (HAS).

HAS affects individual stomata; depends on the amount, thepdeliquescence point and the chaotropicity of particles/ions.

HAS potentially enables stomatal water uptake in fog forests.

Deposited aerosols may be part of stomatal functioningDeposited aerosols may be part of stomatal functioning.

Aerosol pollution potentially decreases drought tolerance.p p y g

Acknowledgements

Knut Wichterich

Effects of Climate Change on Air Pollution and gResponse Strategies for European Ecosystems