Changes in thermal infrared spectra of plants caused by temperature and water stress : powerpoint

(1)

Changes in thermal infrared spectra

caused by temperature and water

stress

Maria Fernanda Buitrago Acevedo Thomas Groen

Chris Hecker Andrew Skidmore

(2)

Context of this research

1

Spectral response of Alpine vegetation in Thermal Infrared

0,4 0,6 0,8 1,0 1,4 _2,0 _3,0 _6,0

Visible

VIS Near Infrared

NIR

Long Wave Infrared LWIR Midwave Infrared MWIR Shortwave Infrared MWIR 8,0…

(3)

Why emissivity in plants

Wavelength Emissivity Emissivity Visible NIR LWIR

Leaf pigments Cell structure Water content

Leaf Biochemicals SWIR

Water - cell structure – leaf biochemicals

Cellulose

Quartz

Starch

(4)

FTIR Spectrometer (laboratory)

3

(5)

Experiment:

Start End

6 months of water and temperature stress

Start End

3 months of water stress

Measurements:

- Leaf Water Content: LWC = 100*(Ww-Wd)/Ww

- Microstructure: Leaf thickness and cuticle thickness

(6)

Experiment:

5 We t Dry Ambient _Cold We t Dry Ambient Cold

Rhododendron (sp.) Beech (Fagus sylvatica)

Water control _{Temperature control}

CW AW AD CD AW AD Temperature Soil w a ter content Temperature

Tracking the same leaves

Soil w

a

ter

(7)

Visual results:

Results W ell w a ter ed Dry Warm Cold 7 14 57 63 CW AW AD CD

(8)

Results: Leaf Water Content (LWC)

7 Leaf Wa te r Con ten t (%)

(9)

Results: Leaf thickness

Lea f Wa te r Con ten t (%) a a b c c c

(10)

Results: Cuticle thickness

(11)

Rhododendron results

Wet / ambient

Dry / cold

Wet / cold Dry / ambient

(12)

Rhododendron results

11 Wet / ambient Dry / cold Wet / cold Dry / ambient MWIR LWIR 0 months 6 months 6 months 6 months 6 months Wavelength (µm)

(13)

Results beech (F. sylvatica)

Dry treatment

Well watered treatment

Dry treatment

0 months 3 months

(14)

Comparison: Rhododendron vs Beech

13

Dry treatment

Beech well watered

Beech dry

Rhododendron well watered

Rhododendron dry 0 months After treatment After treatment Decrease Increase MWIR LWIR

(15)

Results beech (F. sylvatica)

Dry treatment

Well watered treatment

Dry treatment 0 months 3 months 0 months 3 months MWIR LWIR

(16)

15

Possible causes:

Ullah et al. (2013) Water Reflectan ce 2.5 Wavelength 3 3.5 4 4.5 5 5.5

MWIR and changes in LWC:

LWIR: Changes generated by cuticle and cuticular waxes

Photo from: Barthlott & Neinhuis (1997)

Smooth, sunken nervatures.

Photo from: Barthlott & Neinhuis (1998)

Smooth surface, few crystals.

F. sylvatica

Photo from: Gulz, Prasad & Muller (1992)

Rhododendron sp.

Photo from: Hardin & Gensel (1982)

Striated cuticle

(17)

 Stress change the TIR spectral behavior of plants.

 Cold and dry stress have similar responses (visual, LWC, cuticle and leaf thickness)

 Dry treatment cause changes in the 4-6µm region (MWIR), related with changes in LWC.

 TIR spectra shows differences between species in the range 7-12.5µm (LWIR), probably related with biochemistry and microstructure of the leaf, especially complexity of the cuticle.