Radiant energy – Luminophor irradiation
Reexamination Certificate
2001-04-30
2003-05-13
Hannaher, Constantine (Department: 2878)
Radiant energy
Luminophor irradiation
C250S459100
Reexamination Certificate
active
06563122
ABSTRACT:
REFERENCE TO RELATED APPLICATIONS
The present application is the national stage under 35 U.S.C. 371 of international application PCT/EP98/06815 filed Oct. 28, 1998 which designated the United States, and which international application was published under PCT Article 21(2) in the English language.
BACKGROUND OF THE INVENTION
This invention relates to a fluorescence detection assembly for determination of relevant vegetation parameters comprising an excitation source consisting in a low power laser device with an excitation wavelength in the red spectral region, a beam forming optical device, a dichroic beam splitter, a basic fluorescence detector system including an entrance optical device receiving fluorescence emission via said dichroic beam splitter and an interference filter blocking out the elastic back scatter signal, an electronic detection device for detecting a fluorescence signal, and an electronic trigger and timing device.
First of all the phenomenon of chlorophyll fluorescence will be discussed now.
The absorbed photosynthetic active radiation (PAR) of the solar irradiation (380 nm<&lgr;<750 nm) is used by plants primarily to convert the absorbed energy in chemically bound energy (photosynthesis) and stored as chemical energy. This process is directly linked with the uptake of carbon dioxide and the release of oxygen (called primary productivity). Two other pathways are possible for the absorbed energy to keep plants energetically balanced. First, the emission of thermal energy and second, the emission as fluorescence light may be used for regulation.
The thermal energy budget is filled up with solar energy from the visible (VIS) and the short wave infrared (SWIR) range of the solar spectrum. SWIR radiation is directly absorbed by the leaf internal water content. The VIS range contributes via the exciton transfer inside the antenna pigment of the reaction centers (PS I; PS II) and light harvesting complex (LHPC). In this process the absorbed photon energy is transformed to energy quantities required by PS I and PS II. The surplus of energy is stored in oscillating and rotation energy levels and thus finally converted into heat.
At the PS I and PS II the absorbed energy quantities may be used by the so called light reactions, may be transferred to heat or finally emitted as fluorescence light. The emitted fluorescence in the red spectral region is due to the chlorophyll molecules associated to PS I, PS II and the LHPC. The conversion probabilities for heat and fluorescence are considered constant in time, whereas the conversion rate at the light reaction is considered as a function of the state of the reaction center (electron transfer chain) and the phosphorylation state of the photosynthetic active cell membranes. The following Equation (1) will describe the fraction of sun induced chlorophyll fluorescence light (F
Sun
(t)) which is emitted by the reaction centers:
F
Sun
(
t
)
=
k
Fluorescence
k
Fluorescence
+
k
Heat
+
k
Photosynthesis
(
Φ
,
M
)
*
∫
PAR
I
Abs
-
Sun
ⅆ
λ
k
i
:
conversion
probability
for
fluorescence
,
heat
and
photosynthesis
φ
(
t
)
:
state
of
the
reaction
center
M
(
t
)
:
phosphorylation
of
membrane
I
Abs
-
Sun
:
absorbed
spectral
irradiance
.
(
1
)
From this formula it can be seen that the behaviour of the time dependent chlorophyll fluorescence gives access to the relative changes of the photosynthetic activity if one assumes that “&phgr;” and “M” are functions of time.
Detection and interpretation of the chlorophyll fluorescence intensity will be discussed now.
The detection of sun-induced chlorophyll fluorescence is difficult due to the fact that the fluorescence signal is superimposed by the reflected light (passive spectrum). For leaves or plant canopies the fluorescence signal is of the order of only some percent compared to the total signal. Therefore, different measuring techniques applying additional light sources were developed in the past for using the chlorophyll fluorescence for different applications.
In general, a modulated or pulsed light source is added to the sun irradiation “I
Abs-Sun
” inducing a modulated or pulsed fluorescence signal F
add
(t) which superimposes the sun induced fluorescence F
Sun
(t) and the reflected signal IR(&lgr;). Applying a laser source for excitation the so called laser induced fluorescence (LIF) is generated. Equation (1) is then modified to:
F
Sun
(
t
)
+
F
add
(
t
)
=
k
Fluorescence
k
Fluorescence
+
k
Photosynthesis
(
Φ
,
M
)
*
∫
PAR
(
I
Abs
-
Sun
+
I
add
)
ⅆ
λ
.
The total signal which is normally detected is given by the sum of all fluorescence signals and the reflected signal IR(&lgr;). With adequate technical set-up the fluorescence signal excited by an additional light source can be separated from the passive spectrum and the sun induced fluorescence even under daylight conditions at distances, ranging from direct contact (Schreiber 1986, Patent DE 3518527, Mazzinghi 1991, EP 0 434 644 B1) to one meter (Chappelle 1995, U.S. Pat. No. 5,412,219) and several hundred meters (Cecchi and Pantani 1995, EP 0 419 425 B1).
The technical challenge for all systems either for contact measurements as well as for remote measurements is to install an excitation set-up strong enough to induce a sufficiently intense fluorescence signal in order to overcome the passive spectrum and weak enough to keep the photosynthetic system in an unchanged physiological status.
DESCRIPTION OF STATE OF THE ART
In the well known pulse-amplitude-modulation (PAM) fluorometer (Schreiber et al. 1986, Patent DE 3518527) a weak measuring light (light emitting red diode LED) induces the chlorophyll fluorescence via an optical fiber without changing the photosynthetic state of the plant. The fluorescence is transmitted by an optical fiber to a photodiode which detects all fluorescence light above 700 nm. For dark adapted plants no photosynthetic activity is stimulated when the measuring light is on.
Illumination of a dark adapted leaf with an intense flash of several milliseconds up to some seconds duration (called saturating light pulse) gives the maximum available fluorescence (called: Fm) but does not induce photosynthesis. A continuous illumination with non saturating light (called: actinic light) induces photosynthetic activity. After several seconds until minutes of illumination all contributing processes are in equilibrium with the supplied light and thus the fluorescence has reached a steady state value Fs. The transient of the fluorescence during illumination of dark adapted leaves is called Kautzky effect. For example
FIG. 1
shows a measured diagram of a Kautzky kinetic of a cucumber plant. The detected fluorescence at 685 nm is exclusively induced by the laser pulses. Illumination with a 500 W halogen spot light influence the photosynthetic state only and thus k
Photo
. Its contribution to the fluorescence signal, especially as excitation source, is negligible. The PAM fluorometer is normally operated in direct contact with leaves but can be used also at distances of some centimeters.
Detection and interpretation of the Red Fluorescence Ratio will be discussed now.
When excited by UV light, the typical fluorescence spectrum of a plant exhibits two dominant emission bands (FIG.
2
), one from 400 nm-600 nm (called: blue-green fluorescence BG) and one from 650 nm-800 nm (called: red fluorescence; F685, F730). For example
FIG. 2
shows a diagram of the fluorescence emission spectrum of a maize plant grown in the greenhouse. The fluorescence at 685 nm and at 730 nm (called: F685 and F730) originates exclusively from the leaf internal-chlorophyll. The blue-green fluorescence (BG) is emitted pr
Dahn Hans-Günter
Günther Kurt
Lüdeker Wilhelm
Browdy and Neimark
Deutsches Zentrum fur Luft-und Raumfahrt E.V.
Hannaher Constantine
Moran Timothy
LandOfFree
Fluorescence detection assembly for determination of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluorescence detection assembly for determination of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluorescence detection assembly for determination of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3091116