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Introduction
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The method
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Introduction
- Introduction
The delayed fluorescence emission,
natural to all green plants, has been known to scientists for over
fifty decades ...
- The Problem
Modern agriculture relies essentially on herbicides
for managing weeds and the use of herbicides is not foreseen to
diminish in near future. Understanding the mechanism ...
Theory
- The Photosynthetic Apparatus
Photosynthesis of green plants occurs in special
organelles inside the plant cells called chloroplasts. The chloroplasts
have double outer envelope ...
- Photosystem 2
Photosystem 2 is the largest protein complex
found in nature and due to its unique function is also one the
most studied. The holocomplex of PS2 is consisted of some 25 ...
- Chlorophyll Fluorescence
Fluorescence is the light emitted by an excited pigment molecule
upon its return to the ground state ...
- Fluorescence Induction
If a photosynthetic sample is kept for some time in the dark and
then illuminated, its fluorescence will first rise quickly with
time ...
- Delayed Fluorescence
Delayed fluorescence, which is also called
delayed luminescence, delayed light emission, or afterglow, is
the extremely weak light emitted by preilluminated photosynthetic
samples ...
- Induction Curves of Delayed Fluorescence
Like the variable fluorescence, DF undergoes a series of transient changes during the
dark-to-light adaptation of the photosynthetic sample, which are called DF induction ...
- Photosynthetic Herbicides
Over 60% of the herbicides introduced in the last 40 years
act on the chloroplast functions. More than half
of all commercially available herbicides ...
The Method
- Treatment with herbicides
There are several approaches for the application of herbicides
to the target plants - spraying with pulverizer, vacuum infiltration
of leaves, soaking the leaves in
herbicide solution ...
- Principles of DF measurement
A classical apparatus for registration of DF is the
phosphoroscope. It is a rotating disc with perforations (holes) placed
between the light source and the measured sample ...
- Analysis: DFIC of untreated plants
The induction curve of the millisecond delayed fluorescence
of dark-adapted untreated healthy pea leaves, measured at room
temperature under high-intensity actinic light ...
- Analysis: Effects of herbicides on the
DFIC
By inhibiting the electron transport at the acceptor
side of PS2, the herbicides drastically alter the DF properties.
In the presence of herbicides the intensity of DF is suppressed ...
- Analysis: Dose-response curves
The dose-response relationship can be obtained
by measuring the effect of the given herbicide (response) at
a set of different concentrations (doses) ...
Reference
Sidebars
- Fluorescence yield
The term fluoresecence yield, or quantum
yield of fluorescence, φf , references
the number of photons emitted as fluorescence relative to
the total number of absorbed photons ...
- DF kinetic components
At each moment the DF intensity is determined
by the number (concentration) of reaction centres in a state
capable of producing charge recombination ...
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