13.9 Chlorophyll Fluorescence
As mentioned above, there are many ways to improve the agricultural production,
chlorophyll fluorescence is a widely used technique with the aim to monitor the
physiological state of the plant, therefore strongly related with the photosynthetic
process.
The photosynthesis is the main process in the plant, being of great interest
because the carbon, hydrogen, and oxygen assimilated make up *96 % of dry
matter of a typical plant (Taub 2010), and this is reflected on the crop yield.
First, in order to understand the chlorophyll fluorescence, it is necessary to
know that photosynthetic organisms majorly are green, because only the blue and
the red light are absorbed, as we can see in Fig. 13.10, resulting that the human eye
perceive as the photosynthetic organisms on green. Insomuch as the fluorescence
in the plant is a re-emitting energy process with increased wavelength of the
photons previously absorbed. That is why in Fig. 13.10 the fluorescence response
is a little move to the right, because it is consequently of the loss of energy in the
re-emitting (Taiz and Zeiger 2006).
Photosystems (PS) are in charge of this re-emit of photons, there are two
photosystems: PSI and PSII that are containing in chloroplast with thylakoid
membranes. PSI has a very low fluorescence contribution under standard conditions, that is why can be neglected. On the other hand, the PSII is the larger
fluorescence contributor, being the photosystem which the commercial chlorophyll
fluorescence systems commonly perform (Johnson et al. 2009; Stirbet 2011).
The important of the PSII in order to improve the yield crop is constituted by
pigments and proteins in the thylakoid membrane of chloroplast which is closely
related with the stress conditions of the plant (Kautsky and Hirsch 1931). Being
modified the re-emitting of photons by plant in red and far-red of the electromagnetic spectra varying comfort conditions of the plant (Lichtenthaler et al.
2013).
The chlorophyll fluorescence produced by PSII and PSI (last one with a small
contribution) can be used as analytical tool (Belyaeva et al. 2011). It is necessary
to use a fluorometer to measure and analyze the parameter that instrument provide
us.
The fluorometers are constituted mainly by two stages. First stage is the way in
which the photosynthetic sample is excited; this is reached by two different
methods: passive and active methods. Passive methods are when the sample is
excited by sunlight; the main advantage of this technique is that you can save
electronically light source devices but the acquisition of the chlorophyll response
is more complicated due to the environmental noise and lack of control of the light
source (Fernandez-Jaramillo et al. 2012).
On the other hand, the active methods consists in the utilization of light emitter
devices, among which are the Light Emitter Diode (LED) (Faraloni et al. 2011;
Johnson et al. 2009; Kissinger and Wilson 2011; Ji et al. 2010). Lamps such as
halogen (Van Gaalen et al. 2007), xenon that normally it is used on combine of
13 Instrumentation and Control to Improve the Crop Yield
381
As mentioned above, there are many ways to improve the agricultural production,
chlorophyll fluorescence is a widely used technique with the aim to monitor the
physiological state of the plant, therefore strongly related with the photosynthetic
process.
The photosynthesis is the main process in the plant, being of great interest
because the carbon, hydrogen, and oxygen assimilated make up *96 % of dry
matter of a typical plant (Taub 2010), and this is reflected on the crop yield.
First, in order to understand the chlorophyll fluorescence, it is necessary to
know that photosynthetic organisms majorly are green, because only the blue and
the red light are absorbed, as we can see in Fig. 13.10, resulting that the human eye
perceive as the photosynthetic organisms on green. Insomuch as the fluorescence
in the plant is a re-emitting energy process with increased wavelength of the
photons previously absorbed. That is why in Fig. 13.10 the fluorescence response
is a little move to the right, because it is consequently of the loss of energy in the
re-emitting (Taiz and Zeiger 2006).
Photosystems (PS) are in charge of this re-emit of photons, there are two
photosystems: PSI and PSII that are containing in chloroplast with thylakoid
membranes. PSI has a very low fluorescence contribution under standard conditions, that is why can be neglected. On the other hand, the PSII is the larger
fluorescence contributor, being the photosystem which the commercial chlorophyll
fluorescence systems commonly perform (Johnson et al. 2009; Stirbet 2011).
The important of the PSII in order to improve the yield crop is constituted by
pigments and proteins in the thylakoid membrane of chloroplast which is closely
related with the stress conditions of the plant (Kautsky and Hirsch 1931). Being
modified the re-emitting of photons by plant in red and far-red of the electromagnetic spectra varying comfort conditions of the plant (Lichtenthaler et al.
2013).
The chlorophyll fluorescence produced by PSII and PSI (last one with a small
contribution) can be used as analytical tool (Belyaeva et al. 2011). It is necessary
to use a fluorometer to measure and analyze the parameter that instrument provide
us.
The fluorometers are constituted mainly by two stages. First stage is the way in
which the photosynthetic sample is excited; this is reached by two different
methods: passive and active methods. Passive methods are when the sample is
excited by sunlight; the main advantage of this technique is that you can save
electronically light source devices but the acquisition of the chlorophyll response
is more complicated due to the environmental noise and lack of control of the light
source (Fernandez-Jaramillo et al. 2012).
On the other hand, the active methods consists in the utilization of light emitter
devices, among which are the Light Emitter Diode (LED) (Faraloni et al. 2011;
Johnson et al. 2009; Kissinger and Wilson 2011; Ji et al. 2010). Lamps such as
halogen (Van Gaalen et al. 2007), xenon that normally it is used on combine of
13 Instrumentation and Control to Improve the Crop Yield
381