Water deficit and mycorrhizas

Filipi Costa e SilvaHelena AlmeidaDouglas Godbold

Quercus

and ectomycorrhizas

Evidence of involvement in water uptakeNutritional benefits on gas exchange

Juniper and arbuscular

mycorrhizas

Little evidence of involvement in water uptakeNutritional benefits on gas exchange

-

Portugal Alcácer

do Sal

Populus

alba

Populus

euphratica

Water

stress

-

Portugal Alcácer

do SalWatering

regimes

Moderate stress  (45% ETO)Well watered

(75% ETO)

Populus

albaNorthern ecotype

(6K3)    Southern ecotype

(2ASA2)

Populus

euphratica

Drought and salinity

020406080

100120

MS 2AS MS 6K3 SS 2AS SS 6K3

Hei

ght (

cm)

0.0

0.5

1.0

1.5

2.0

Dia

met

er (c

m)

Height (cm) Diameter (cm)

Populus albaSevere

stressed plants of both ecotypes

showed significant lower values of height and diameter (p<0.01)

Plants of the southern ecotyp

e

2AS showed higher height and diameter

than the northern ecotype 6K3 plants in moderate stress

conditions

Leaf stomatal conductance (moderate stress treatments)

plants of the southern genotype 2AS kept higher values of gs

in the morning (10h) than the northern 6K3 plants throughout the summer

050

100150200250300350400450

Jun Jul Aug Sept

gs (m

mol

. m-2

. sec

-1)

2AS (10h) 6K3 (10h)

Portugal Alcácer

do Sal

Populus

alba

and Populus

euphratica

Ectomycorrhizal

and arbuscular

mycorrhiza

Ectomycorrhizal

colonisationpe

rcen

tage

col

onis

atio

n

0

10

20

30

40

50

Water stress 45% ET

Watered 75% ET

2ASA4 tolerant6K3 sensitive

ECTOMYCORRHIZAL MORPHOTYPES

Ectomycorrhizal

morphotypes

2AS4A   (T) water

stress

6K3        (T) water

stress

2AS4A   (S)  watered6K3        (S)  watered

morphotype

perc

enta

ge c

olon

isat

ion

0

5

10

15

202ASA4 tolerant6K3 sensitive

Wooly Brown Silver Black Unknown

45%75%

Ectomycorrhizal

morphotypes

More water benefits some morphotypes

water stress

watered

morphotype

perc

enta

ge c

olon

isat

ion

02468

10121416

Wooly Brown Silver Black Unknown

45%75%

Arbuscular mycorrhizas

Total colonisation

Vesicular colonisation

perc

enta

ge c

olon

isat

ion

0

2

4

6

8

Water stress 45% ET

Watered 75% ET

perc

enta

ge c

olon

isat

ion

0

10

20

30

40

50

Water stress 45% ET

Watered 75% ET

2ASA4 tolerant6K3 sensitive

What controls change in ectomycorrhizal assemblage?

Higher belowground C investment?Sensitivity of the mycorrhizas?

Populus euphratica

Drought and salinity

% m

ycor

rhiz

atio

n

05

1015202530354045

A B

Dry SoilW et SoilRoots in W ater

Populus

euphratica

at En Avedat

0

100

200

300

400

500

600

2AS 6K3 P euphr

nº fo

rks

/ Roo

t len

ght (

m)

0

100

200

300

400

500

600

700

Roo

t len

ght /

soi

l vol

ume

(m.m

-3)nºforks/RL

RL/soil volume

P. euphratica showed a noticeable higher root branching

(+76%) and root

lenght per soil volume (+194%) than P. alba

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

2AS 6K3 P euphr

Leaf

/ R

oot a

rea

ratio

020406080100120140160

SLA

(cm

2 g-1

)

LA/RASLA

2AS ecotype showed a higher leaf / root area ratio

(+66%) than 6K3

P. euphratica showed a

noticeable lower leaf / root area ratio(-92%, on average) than P. alba

But

Populus euphratica least drought tolerant

Stressed

Populus

maintain

abundant mycorrhizas

NM     NM+Na

Myc

Myc+Na

Hydraulic redistribution

Querejeta et al 2003

Growth in soils by  arbuscular

mycorrhizal

hyphae

lowers changes  in matrix potential in 

drying soils

Augé

et al 2001

AM spore numbers

Acaulaspora

Scutellaspora

More water decreases spore number

Spore size (um)

spor

es k

g-1 s

oil

0

200

400

600

500 125

2ASA4 tolerant6K3 sensitive

Total

45%75%