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Chlorophyll fluorescence: A wonderful tool to study plant physiology and plant stress . Presented by: Zia Amjad Presented to: Prof . Dr Ali Abdullah Alderfasi. Chlorophyll Fluorescence. - PowerPoint PPT Presentation
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Chlorophyll fluorescence: A
wonderful tool to study plant
physiology and plant stress Presented by:Zia AmjadPresented to:Prof. Dr Ali Abdullah Alderfasi
Chlorophyll Fluorescence Plant chlorophyll fluorescence technology was developed in the 1990s. The
variation in fluorescence can be shown by false color images or as numerical
values from the photochemical reaction kinetics (quantum yield,
fluorescence decline, non-photosynthetic quenching).
Chlorophyll Fluorescence Photosynthesis belongs to ones of the oldest photo-physical and biochemical
processes on Earth. A large progress in the research of photosynthesizing organisms
was achieved at the end of 20th century by the introduction of modern optical
methods and techniques allowing to study photosynthetic processes ranging from the
subcellular up to the plant canopy level.
Chlorophyll (Chl) fluorescence:
These techniques appeared to be a very powerful tool for studying of photochemical and
non-photochemical processes within thylakoid membranes, chloroplasts, plant tissues, or
whole plants.
Chlorophyll Fluorescence Photosynthesis is the primary process by which plants synthesize food and maintain energy. As part
of that process some energy is released as light or fluorescence, commonly in the chlorophyll
pigment areas in the leaf.
This chlorophyll fluorescence can be measured using the Chlorophyll Fluorescence meter to provide
an inside look at the efficiency of the photosynthetic process or its disruption due to stress related
factors.
Applications:
• Photosynthesis research
• Plant ecology
• Stress physiology
• Terrestrial / aquatic plants
• Information from whole leaf to single cells
• Detecting phytotoxic compounds
Chlorophyll fluorescence measurements in plantsby : J. Leipner
Light energy that is absorbed by chlorophyll in a leaf can undergo three
fates:
a) It can be used to drive photosynthesis (photochemistry).
b) It can be dissipated as heat.
c) It can be re-emitted as red fluorescence.
Absorption and emission spectrum of chlorophyll
Chlorophyll fluorescence measurements in plantsby : J. Leipner
These three process occur in competition.
Any increase in the efficiency of one process will result in a decrease in the
yield of the other two.
Therefore, determining the yield of chlorophyll fluorescence will give
information about changes in the efficiency of photochemistry and heat
dissipation.
Possible fates of excited chlorophyll
Measurement of chlorophyll fluorescence by the saturation pulse method (adapted from Van Kooten & Snell, 1990).
The most useful and widely used chlorophyll fluorescence technique is the so-called
quenching analysis of modulated fluorescence by the saturation pulse method.
A leaf is dark adapted for at least 15 min (depending on temperature) prior to the
measurement.
Upon the application of a saturating flash (about 8000 µmol m-2 s-1 for 0.6 - 1 s),
fluorescence raises from the ground state value (Fo), which is the fluorescence
determined in darkness by a weak measuring beam, to its maximum value, namely
Fm.
This measurement allows the determination of the maximum quantum efficiency of
photosystem II (PSII) primary photochemistry, given as
Fv/Fm
Need for understanding the basic theoretical principles of Chl-fluorescence
Because the basic theoretical principle explains the emission of Chl-fluorescence and its
connection with photochemical and non-photochemical processes working within thylakoid
membranes under light excitation as well as physiological aspects of plant stress.
Theoretical background:
1)- Thylakoid membrane and linear electron transport:
Chlorophyll fluorescence is defined as “The Chl fluorescence is a physical signal defined as a
radiative energy evolved from deexciting Chl a molecules (λ = 690 nm for PS II, λ = 740 nm for PS
I)”.
OR
Chlorophyll fluorescence is light that has been re-emitted after being absorbed by chlorophyll
molecules of plant leaves.
By measuring the intensity and nature of this fluorescence, plant ecophysiology can be investigated.
1)- Thylakoid membrane and linear electron transport:
Brief structural overview of thylakoid membrane with a special
respect to those components that may affect Chl-fluorescence
signals.
Salinity Stress
Salinity Stress
Salinity Stress
Chilling Stress
Chilling Stress
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