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18.02.14, 3rd IPPS, Chennai, India

Emerging sensors and non-invasive methods for the

rapid and accurate estimation of water status in above-

ground plant tissues

Fabio Fiorani

Institute of Bio- and Geosciences IBG-2: Plant Sciences

Jülich Plant Phenotyping Center

Plant phenotyping science requires integrated solutions

‣ Non-invasive sensors: brief, state-of-the-art overview

‣ Measuring leaves water status non-invasively

• spectral reflectance NIR, SWIR regions: some considerations

• Passive thermography: is there room for improvement?

• New promising non-imaging sensors at IBG2

Towards dynamic and quantitative analyses of water status for shoots and leaves: exciting developments

Non-invasive technologies are key to quantify plant structure and function

Fiorani, Jahnke, Rascher, Schurr, Curr Op Biotech (2012)

Parameters Method Resolution Pros Cons

Shoot biomass, seedling vigor, color, shape descriptors,

root architecture, seed morphology and surface features,

leaf disease assessments

RGB Whole organs or

organ parts;

minutes/days

Rapid measurements,

affordable solutions

Limited physiological

information

PSII status, disease severity Fluorescence Whole shoot/ leaf

tissue; minutes

/days

Probe of PSII

photochemistry in vivo

Only for rosettes; pre-

acclimation conditions

Surface temperature Thermal Whole shoot, or leaf

tissue; time series

minutes/days

Rapid, potential

information about leaf and

canopy transpiration

Sound bio-physical

interpretation required

Water content, seed composition NIR, multispectral Time series or single

time point analyses

of shoots and

canopies; single

seeds

Estimates of biomass

composition by

chemometric methods

Extensive calibration

required

Biomass, leaf and canopy water status, disease severity,

pigment composition

NIR, multi-

hyperspectralther

mal

Vegetation cycles

outdoor/indoor

Large amount of

information

Cost; illumination

conditions; large image

datasets; complex data

interpretation

2D (spatial) dimensions imaging: pros and cons

Fiorani & Schurr, Ann Rev Plant Biol (2013)

Operational capacity for non-invasive phenotyping of whole plants

MAX CAPACITY SPECIES EXP. VARIABLES

2500

300

300

72 (1 plant/rhizobox)

Arabidopsis Rosette species

Arabidopsis Small seedlings

Monocots Dicots

Monocots Dicots

• Reduced water

• Nutrients (N, P)

• Temperature • CO2

• Reduced water • Nutrients (N, P)

• Nutrients (N, P)

• Temperature • Osmotic

• Nutrients

• Reduced water • Soil compaction

Remote sensing group – Uwe Rascher

Fiorani et al., Current Opinion Biotechnology, 2012 Mueller-Linow et al., in preparation

Development of field platforms at IBG2

Parameters Method Resolution Pros Cons

Shoot structure , leaf angles distribution,

canopy structure

Stereo camera systems Whole shoots

time series at

various

resolutions

High 3D accuracy; shoot

and canopy models

Complex data

reconstruction

Shoot biomass and structure, leaf angles distributions,

canopy structure

Laser scanning

instruments with

widely different range;

Time-of-flight cameras

Whole shoots

time series at

various

resolutions

High 3D accuracy; shoot

and canopy models

Some laser scanning

instruments require

specific illumination

Morphometric parameters in 3D X-ray tomographs

100 µm and

lower; hours

3D root analyses

enabled

X-ray source

effects for imaging time

series to be evaluated

Morphometric parameters in 3D, water content Magnetic resonance

imagers

200-500 µm; 1-

600 sec

3D root analyses

enabled

Ferromagnetic elements

in soil need to be

removed

Transport partitioning, sectorality, flow velocity Positron emission

detectors10 for short-

lived isotopes e.g., 11CO2

1-2 mm; 10 sec -

20 min

Short term

measurements of in vivo

carbon flow

Access to short-lived

radiotracers

3D (spatial) and volumetric imaging: pros and cons

Fiorani & Schurr, Ann Rev Plant Biol (2013)

Measuring leaf water status is still mostly based on destructive sampling

Varying leaf thickness is a key factor to account for in calculating water indices by spectral reflectance

Measuring water status and transpiration efficiency: how far can we go with thermography

Solar radiation (S) received by the land surface is partitioned to latent (λE), sensible heat (H) and long wave radiation (εσT4) fluxes. Stomata are at the choke point. (from Sellers et al. 1997)

Tleaf – Tair ~ rate of transpiration

oversimplification

19.5

20.0

20.5

21.0

21.5

22.0

22.5

23.0

23.5

24.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

light on light off

T (oC)

Days

Thermography data need careful interpretation

T leaf

T soil

Measuring time constants with an active thermography approach

Cavity resonance for biomass measurements

Menzel et al., 2009

0 100 200 300

0

2

4

6

8

10

f

(MH

z)Position (mm)

1130 1140 1150 1160

-30

-20

-10

Am

pli

tud

e (d

B)

Frequency (MGz)

Response

Integral

Redevelopment of the concept for use in a scanning mode and for plants of various size

6 7 8 9 10 11 12

0

200Night

0—20

20—40

40—60

60—80

80—100

100—120

120—140

Inte

gral

Time (Days)

+20mL water

Day

Stem

Stem and leaves

Position-dependent responses are meaningful especially for some shoot geometries

0

20

40

60

80

100

120

0 500 1000 1500 2000

Am

pli

tud

e (

a.u

.)

time (ms)

60

70

80

90

100

110

120

0 0.05 0.10

10

20

30

40

50

60

70

80

90

100

0 50 100

I

II

baI: total proton density:

liquids + solids

II: proton density liquids

III: proton density solids

III

Example (FID-CPMG) curve: mature bean pod

Sensor-like applications: measurement principle

Many applications are possible

rice leaves wheat ear oak bean pod

100

200

300

400

500

07/04 08/04 09/04 10/04 11/04 12/04 13/04 14/04 15/04 16/04 17/04 18/04 19/04 20/04 21/04

time (days)

am

pli

tud

e (

%)

3

7

10

14

1 2 3 4 5 6 7 8 9 10 11 12 13 14

vo

lum

e o

f w

ate

r (%

)

Amplitude liquids/Amplitude soilds+liquids

‣ Together with applying spectral reflectance, we

have continued the development of new methods

‣ Active thermography opens new possibilities and

has potential for application in the lab and in the field

‣ Portable NMR and cavity resonance provide sensitive

methods for high-resolution dynamic changes of water status

Acknowledgments

Hendrik Albrecht Carel Windt Viktor Sydoruk

Siegfried Jahnke Uwe Rascher Roland Pieruschka

Mem

ber

of

the H

elm

holtz A

ssocia

tion

Studying plants dynamics in heterogenous environments

IBG2: Plant Sciences