Imaging hydraulic failures in trees using x-ray microtomography

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HAL Id: hal-01268527

https://hal.archives-ouvertes.fr/hal-01268527

Submitted on 5 Jun 2020

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Imaging hydraulic failures in trees using x-ray

microtomography

Eric Badel

To cite this version:

Eric Badel. Imaging hydraulic failures in trees using x-ray microtomography. Colloque Xylème, May

2014, Besse, France. pp.22. �hal-01268527�

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Imaging hydraulic failures in

trees by x-ray microtomography

Eric BADEL

Hervé COCHARD

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2D X-ray radiography

X-ray

source

thin

sample

2D

detector

0 ln(

I

)

e

I

= −

µ

µ : X-ray absorption is a function of :

- atomic components

- matter density

- incident x-ray energy

e,

µ

I

₀

I

Röntgen 1895

I

₀

I

• integrative information throught the thickness

• spatial resolution is a function of sample

thickness and tomographic components (X-ray

spot size, detector…)

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2-D X-ray tomography

Microfocus

X-ray source

Medical scanner

(low resolution)

2D tomography

(high resolution)

High resolution

detector

0 0 .0 2 0 .0 4 0 .0 6 0 .0 8 0 .1 0 0 - ln ( I / I₀ )

θ

=

0

(5)

The 3D

µ

tomography

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Few X-ray tools

Small lab device

Lab device

Synchrotrons lights

X-ray

polychromatic

monochromatic

Beam

divergent

parallel

Spatial resolution

5-10 microns

1 micron

0.3 micron

Max sample size

4-5 cm

10 cm

1 mm

File size

16 Go

32 Go

64 Go or more

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• very high x-ray intensity

• fast scan time

• the sample chamber is huge

(but the scanned area is not larger than

for the lab tools)

• access after a proposal

• short time experiments

• huge data to manage (1-4 To /j)

• very tiring

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3D hydraulic network observation

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Embolism measurements

0

r

0 . 5 1

CAVITRON

P50

Vulnerability curve

Cochard et al 2005

Increasing tension and measurement of the loss of conductivity

The big issue: not available for long vessels species

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Embolism observation and measurments

200 µm

Walnut tree

Pinus sylvestris

100 µm

Douglas

(12)

What did we learn about embolism

process

thanks to X-ray tomography?

Few experiments using synchrotron radiations or

our Nanotom (Clermont-Ferrand)

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light stimulation, fan, root stress => tension in hydraulic conduits

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Live embolism spreading observation (poplar tree)

0

25

50

75

100

0

1

2

3 y=100/(1+exp(a*(x-b))), r

2

=0.993

a=-4.50, b=1.80

Pressure (MPa)

L

o

s

o

f

c

o

n

d

u

c

ti

v

it

y

(%

)

10 min / scan using

synchrotron radiation

(Swiss Light Source)

3H

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3H

Live embolism spreading observation (oak tree)

Cavitron

X-ray images

0 20 40 60 80 100 1 2 3 4 5 6 y=100/(1+exp(a*(x-b))), r2_=0.89 a=-1.2, b=4.3

Pressure (MPa)

L

o

s

o

f

c

o

n

d

u

c

ti

v

it

y

(

%

)

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Laurus: long vessels species

Indirect methods

Direct micro-CT

Salleo & Lo Gullo 1993 Salleo et al 2000 Hacke & Sperry 2003 Trifilo et al 2014a Trifilo et al 2014b Salleo et al 1996 Tyree et al 1998 Hacke & Sperry 2003 Salleo et al 2004 Salleo et al 2006 Salleo et al 2009 Cochard 2002 dehydration centrifugation Dehydration Air injection Centrifugation

Xylem pressure, MPa

-6 -5 -4 -3 -2 -1 0

P

er

c

e

n

t

x

y

le

m

e

m

b

o

li

sm

0 20 40 60 80 100

-1 MPa

-3 MPa

-6 MPa

Long vessel species , with big vessels do not show ‘R’ shaped

vulnerability curve and can be very resistant!

(Cochard, Delzon and Badel , submitted)

100%

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Embolism start

At the annual ring level, embolism is not a random process!

Poplar

Douglas

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Embolism spreading

-1.5 MPa

?

At the cell level, lonely seeds of embolism start more or less

randomly; then spreading occurs in radial direction.

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-20°< T°

<+5°

0 30000 60000 90000 120000 0 20 40 60 80 100 A E c u m ( % ) -45 -30 -15 0 15 T e m p e ra tu re ( °C )