Dr. Kumud B. Mishra
Global Change Research Centre ASCR, vvi,
Bělidla 986/4a, 603 00 Brno
Email: mishra.k@czechglobe.cz
Optical properties of leaves and its implication in understanding
plants functional properties and primary production
ProdukProdukččnníí biologie Bi8030biologie Bi8030
podzimnpodzimníí semestr 2014semestr 2014
Stomata: 10-5 m
Leaf: 0.01-0.1 m
Plant: 1-10 m
Canopy: 100-1000 m
Landscape: 1-100 km
Continent: 1000 km
(106 m)
Globe: 10,000 km (107 m)
Bacteria/Chloroplast: 10-6 m
Spatial Scales of Inquiry:
Span 13-14 orders of Magnitude
Spatial Scales of Inquiry:
Span 13-14 orders of Magnitude
mm - cm
cm - m
m - km
/spatial resolution/
AISA Eagle
Fs & QY NDVI PRI
Multi-scale monitoring
Photon-leaf interactions
Plant leaves and its function
•Producing food and oxygen through
photosynthesis
•Balancing water loss
•Regulating gas exchange
•Transporting products of
photosynthesis
Plant leaves and its function
•Producing food and oxygen through
photosynthesis
•Balancing water loss
•Regulating gas exchange
•Transporting products of
photosynthesis
Diagram of the internal structure of a leaf
Photon-leaf interactions
Cross section of leaves
Cuticle:
Upper epidermis:
Preventing water loss, providing an extra layer
between the outside and inside of the leaf.
Mesophyll.
-palisade layer
Chloroplast; photosynthesis, food & O2
-spongy layer
vascular bundles: xylem and phloem
Lower Epidermis
Stomata
Upper cuticle
palisade
Spongy
Photon-leaf interactions
Leaves: Cuticle & Epidermis
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Heredia-Guerrero et al.(2014)
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Waxy layer: (hydrophobic)
-prevent water loss,
-first defense against pests and pathogen
-reflect UV light
-self cleaning (Lotus)Deposition
of pathogens
Sunlight blocking particles
Phenolics:
-UV screening,
-Antioxidant,
-changes with environment, stresses
Photon-leaf interactionsLocalization of different subgroups of phenolics at tissues and cellular level
Karabourniotis et al. (2014) Plant Science 227:21-27
Photon-leaf interactionsSpectral regions of absorption maxima of compounds in leaves epidermis
Cerovic et al.(2002) Plant Cell and Environment, 25: 1663-1676
Photon-leaf interactions
Cerovic et al.(2002) Plant Cell and Environment, 25: 1663-1676
Spectral regions of absorption maxima of compounds in leaves epidermis
Photon-leaf interactionsHow to measure compounds in the Leaf epidermis?
Cerovic et al.(2002) Plant Cell and Environment, 25: 1663-1676
-Extraction of leaf cuticle and measurements of absorbance and transmittance
Krauss et al. (1997) Plant, Cell, and Environment 1997
Problems in measuring epidermis contents by leaf extraction:
leaf structures on UV absorption, and the local distribution of phenylpropanoids
in leaves are lost by the extraction procedures.
ChlF excitation ratio (FER) = ChlF yields [UV / blue-green excitations]
Log(FER)= absorbance of leaf epidermal
Photon-leaf interactionsHow to measure compounds in the cuticle?
Cerovic et al.(2002) Plant Cell and Environment, 25: 1663-1676
ChlF excitation ratio (FER) = ChlF yields [UV / blue-green excitations]
Log(FER)= absorbance of leaf epidermal
Photon-leaf interactionsFER can measure absorbance of leaf epidermis
Cerovic et al.(2002) Plant Cell and Environment, 25: 1663-1676
Photon-leaf interactions
Leaves: Mesophyll & Lower Epidermis
palisade layer
-cells are tall,
-closely packed to absorb
maximum light.
-many chloroplasts.
-most photosynthesis takes
place in the palisade cells.
-photosynthesis,
- food
-O2
spongy layer
vascular bundles:
- xylem & phloem
Lower Epidermis
Stomata
Biochemical leaf composition
A typical cell of green fresh leaf contains:
-Water (vacuole) 90-95%
-dry matter : 5-10 %
• Cellulose 15-10 %
•Hemicellulose 10-30%
•Proteins 10-20%]
•Lignin 5-15%
•Starch 0.2-2.7%
•Sugar
•Chloroplasts (Chlorophyll a, b)
•Other pigments (Carotenoids, anthocynin, brown
pigments,Flavons, etc.)
Photon-leaf interactions
Photosynthesis
Reflectance
Transmitted light
Heat
Blue-green Fluorescence
Absorption
Chlorophyll fluorescence
Energy conservation: R(l) + T(l) + A(l) = 1
Schematic diagram representing interaction of
plant’s leaf with light
Light
Schematic diagram representing interaction of
plant’s leaf with light
Reflectance and fluorescence signals
Water absorption
Govindjee (2004)
Reflectance is being measured at various
level and many vegetation indexes has
been derived.
Steady state Fluorescence at Fraunhofer
lines will be measured in proposed FLEX
mission
Water
Chlorophyll fluorescence competes with photosynthesis for excitation energy
ChlF can be used as a non –invasive reporter to study
photosynthetic yield
S0
S1
S2
Chla
hννννblue
photosynthesis
Fluorescence hννννNIR
Heat
S0
S1
S2
Chla
hννννblue
photosynthesisphotosynthesis
Fluorescence hννννNIR
Heat
Fluorescence hννννNIR
Heat
Chlorophyll fluorescence competes with photosynthesis for excitation energy
Photon-leaf interactions
Integrating sphere for accurately measurements of
reflectance
Propagation of photons in leaf
Spectral properties: effect of leaf pigments
Spectral properties: effect of leaf internal structure
VEGETATION INDEX: Two wavelength dependent Indexes
0
20
40
60
80
100
120
400
430
459
488
517
547
576
605
634
663
692
721
749
778
807
835
864
892
Wavelength (nm)
Reflectance
531 nm 570 nm
PRI = (R531-R570)/( R531+R570)
R531 is sensitive to change in Xanth’s Cycle Epoxidation state
R570 is a reference, unaffected by Xanth’s Cycle Epoxidation state.
Quite high variability in day, hours, minutes and even second.
Seasonal variability is also seen
NDVI = (Rfar-red-Rred)/( Rfar-red+Rred)
PRI - a way of dissipating excess light to
protect the photosynthetic apparatus (Gamon
et al. 1990).
conversion of violaxanthin to zeaxanthin
through xanthophyll cycle.
Low
Light
High
Lght
Change in De-epoxidation state of Xanthophylls cycle
could be detected by measuring PRI
Photochemical reflectance index (PRI)
Normalized Differential Vegetation Index (NDVI)
VEGETATION INDEX: Three wavelength dependent Indexes
a = Sum of the Absorption coefficients for the pigments of interest ap and other pigments a0
bb = Backscattering coefficient
1 1
1 2 3[ ( ) ( ) ] ( ) pR R R aλ λ λ− −
− × ∝
R(λ)1 = Reflectance maximally sensitive to the absorption of particular pigments ap
R(λ)2 = Reflectance where the absorption is much lower than R(λ)1
R(λ)3 = Reflectance where backscattering controls the reflectance
1
/ bR R a b−
∞∝ =
Gitelson et al (2006)
Three wavelength dependent indices proved to be very useful for tracking of particular pigments.
Table: Spectral bands for retrieving pigment content from leaf reflectance
Water
SurfaceConductance
Transpiration/
Evaporation
Available
Energy
Photosynthesis/
Respiration
LAI
Carbon
Nutrients
Litter
Soil Moisture
PBL ht
Sensible Heat
System Complexity:
Interconnection of Key Ecosystem Processes
Remote sensing of vegetation products scaling of biophysical processes : A challenge
Leaf area index (LAI) = Leaf area per unit ground surface area
= leaf area / ground area, m2 / m2)
~ projected leaf area m2
Fraction of absorbed photosynthetic active radiation (fPAR)
= radiation absorbed by vegetation for photosynthesis
/ total incoming PAR between 400–720 nm
• Primary productivity of photosynthesis
• evapotranspiration
• reference tool for crop growth
How to measure LAI?
Direct Methods
-Area harvest (grasslands, agriculture)
-application of allometric equations to stand diameter data,
-leaf litterfall
collect leaves during leaf fall in traps and compare to area measurements. Leaf are is
measured using a scanner and image processing software collect leaves from the
canopy and conduct measurements. Is destructive, especially with evergreens due to
the difficulties and destructiveness of direct methods for determining LAI, they are
mostly used as a reference for indirect methods that are easier and faster to apply.
disadvantages include:
Destructive; time consuming; expensive, especially if the study are is large
Indirect Methods
indirect contact LAI measurements (very subjective
and labor intensive)
plumb lines inclined point quadrates
indirect non-contact measurements (typically preferred)
hemispherical photography: estimate LAI from
analyzing upward looking fisheye photographs
taken beneath the plant canopy
How to measure LAI?
Beer’s Law predicts light transmission through a turbid medium, in terms
of the relative light transmission (I/Io), as an exponential function of leaf
area index (L) and a proportionality constant (k); k reflects the geometric
influence associated with the angle
between leaves and the sun:
I/I0=exp(-kL)
How to measure LAI?
Remote sensing of vegetation products scaling of biophysical processes : A challenge
Leaf area index (LAI) = Leaf area per unit ground surface area
= leaf area / ground area, m2 / m2)
LAI ranges from zero (bare ground) to over 10 (dense conifer forests
Remote sensing of vegetation products scaling of biophysical processes : A challenge
Leaf area index (LAI) = Leaf area per unit ground surface area
= leaf area / ground area, m2 / m2)
LAI
How to measure LAI?
tropical rain forest
LAI= 6-10
pines trees
LAI = 2 - 4)
temperate deciduous
forest
LAI = 3 - 5
fAPAR= a*NDVItoc + b
APAR = fAPAR*PAR
GPP = ε n(a*NDVI+b)PAR∑
NPP= GPP- R ( autotropic)
Net ecosystem exchange of CO2 (g C m-2 time-1) NEE= GPP- R total
R
total
is the sum of all autotrophic and hetrotrophic respiration over some time period (Hunt et al. 2002)
GPP can be calculated from remotely sensed NDVI
Direct and indirect methods for estimation of LAI, fAPAR, and modeling NPP of different types of terrestrial ecosystems
Gower et al. (1999)
• NDVI has been applied in innumerable studies for estimation of vegetation biomass, greenness,
primary production, dominant species, leaf are index (LAI), fraction of absorbed
photosynthetically active radiation (fAPAR)
The TERRA, EOS-AM platform was launched on December 19, 1999 and started to provide global primary
production (namely, MOD17) on the 8-day interval with nominal 1-km resolution beginning on Feb 24, 2000
(Zhao et al. 2005).
Turner et al. (2006) tested the performance of NPP and GPP on nine sites varying widely in biome types and land
use, and concluded an over estimation at low productivity sites and underestimation at higher productivity site of
these parameters while comparing satellite and eddy co-variance technique.
Productivity Estimation