M.D. Fariñas, Tomás E. Gómez Álvarez-Arenas, D. Sancho-Knapik*, J.J. Peguero-Pina* and E. Gil-Pelegrín*

UMEDIA, CSIC, Serrano 144, 28006, Madrid, Spain *: Unidad de Recursos Forestales, CITA, Gobierno de Aragón, Zaragoza, Spain

SHEAR WAVES IN VEGETAL TISSUES AT ULTRASONIC FREQUENCIES

Effective leaf parameters for normal incidence

Thickness

(µm)

Density

(kg/m3)

Velocity

(m/s)

Attenuation

(Np/m)

Epipremnum aureum (model: one layer,

effective properties) 340 1000 170

640 (246 kHz)

Epipremnum aureum I. Palisade parenchyma II. Spongy mesophyll

170 170

1200 400

500 155

590 590

Vitis v. (model: one layer, effective

properties) 295 890 315

800 (531 kHz)

Vitis v. I. Palisade parenchyma

II. Spongy mesophyll

147 147

950 678

500 274

750 750

Variation of Epipremnum aureum leaf properties during

dehydratation

Transmission coefficient in Epipremnun aureum leaf versus

frequency at incidence angle of 30º during dehydratation

Calculated values of the magnitude and phase spectrum

(two layers model-Solid line, one layer model-Dashed line)

Effective leaf parameters at oblique incidence

Poisson’s

ratio

Shear

wave

Velocity

(m/s)

Shear wave

Attenuation

(Np/m)

Epipremnum aureum I. Palisade parenchyma

II. Spongy mesophyll

0.35 0.35

240 75

1032

(246 kHz)

Vitis vinifera I. Palisade parenchyma

II. Spongy mesophyll

0.35 0.35

245 135

1600

(531 kHz)

-80

-70

-60

-50

-40

-30

Transmission coefficient. Epipremnum aureum

Am

plit

ude (

dB

)

a)

-4

-3

-2

-1

0

1

2

3 P

hase

(ra

d)

= 00

-80

-70

-60

-50

-40

-30

d)

c)

b)

Am

plit

ude (

dB

)

-4

-3

-2

-1

0

1

2

3

Phase

(ra

d)

= 100

-80

-70

-60

-50

-40

-30

Am

plit

ude (

dB

)

-4

-3

-2

-1

0

1

2

3

Phase

(ra

d)

= 200

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

-80

-70

-60

-50

-40

-30

Am

plit

ude (

dB

)

Frequency (MHz)

-4

-3

-2

-1

0

1

2

3

Phase

(ra

d)

= 350

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

-80

-70

-60

-50

-40

-30

Transmission coefficient, Epipremnum aureum

Am

plit

ude

(d

B)

o

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

-5

-4

-3

-2

-1

0

Ph

ase

(ra

d)

Frequency (MHz)

0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34 0.36 0.38

0

50

100

150

200

-60

-55

-50

-45

-40

-35

-30

Time (min)

Frequency (MHz)

Am

plitu

de

(d

B)

-55

-50

-45

-40

-35

Experimental results I. Normal incidence:

determination of mean parameters of the layered

model of the leaf

Layered model for the leaf: analysis of the thickness resonance

spectra over a wide frequency window

0,19

0,20

0,21

0,22

0,23

Epipremnum aureum

Re

so

na

nt

fre

qu

en

cy (

MH

z)

shear

longitudinal

Turgor Loss Point

1000

1500

2000

2500

Att

enu

atio

n c

oe

ffic

ient

/Np

/m)

0,92 0,94 0,96 0,98 1,00

160

200

240

280

320

360

400

440longitudinal

shear

Ve

locity (

m/s

)

RWC

0,33

0,34

0,35

0,36

0,37

0,38

0,39

0,40

Po

isso

n's

ra

tio

-60

-55

-50

-45

-40

-35

Transmission coefficient. Vitis vinifera

Am

plit

ude (

dB

)

-3

-2

-1

0

1

2

Phase (

rad)

= 00

-60

-55

-50

-45

-40

-35

Am

plit

ude (

dB

)

-3

-2

-1

0

1

2

Phase (

rad)

= 100

-60

-55

-50

-45

-40

-35

Am

plit

ude (

dB

)

-3

-2

-1

0

1

2

Phase (

rad)

= 200

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

-60

-55

-50

-45

-40

-35

Am

plit

ude (

dB

)

Frequency (MHz)

-3

-2

-1

0

1

2

Phase (

rad)

= 300

Experimental results II. Oblique incidence :

determination of leaf shear properties

Magnitude and phase spectra of the transmission

coefficient versus frequency at several incidence angles

• A bilayer acoustic model for the leaf has been developed in order to correctly extract leaf properties from measured spectra

• Shear waves are generated and detected using a trough transmission technique, oblique incidence, wideband air-coupled

ultrasounds and spectral analysis of the transmission coefficient (magnitude and phase).

• In Vitis Vinifera shear waves presence strongly depends on the degree of development of the leaf: shear waves are detected

for leaves collected in summer and fall, but there is no sign for leaves collected in spring

• Analysis of shear waves in plant leaves can be used to monitor leaf water content changes.

Variation of shear wave properties during leaf

Dehydratation

Shear Waves are observed in leaves of some plant species (Epipremnum aureum and Vitis vinifera) using air-coupled ultrasound and a through transmission technique at

oblique incidence. Shear waves appeared as a modification of the thickness resonance pattern of the longitudinal wave measured at normal incidence. Poisson’s ratio, shear

wave velocity and attenuation of shear waves in the leaves are extracted from the measured resonance spectra using a two-layered model. Influence of water content or the

degree of leaf development on shear wave properties is also analyzed.

2

2

3

4

3

1

md.farinas@csic.es tgomez@ia.cetef.csic.es

https://sites.google.com/site/umediaresearchgroup/IUS-2012