Dear Sagar S. Jagtap,

FLUORESCENCE: We can measure two types of fluorescence: prompt (PF) and delayed fluorescence (DF, also named luminescence). Both types are emitted from PSII.

PF results from deactivation/de-excitation of the lowest singlet excited states of chlorophyll a, within the photosynthetic unit (chlorophylls + light harvesting protein complexes LHC + reaction center P680 + oxygen evolving complex OEC). The quantum yield of PF depends on photochemical (PQ) and non-photochemical quenching (NPQ) processes.

PQ can be defined as the PSII capacity to trap photons energy into excitonic energy, resulting in a excited reaction center (P680*) generating positive and negative charge pairs CP.

In NPQ, the excitonic energy is transformed into heat (sink, radiative energy dissipation).

DF is the result of deactivation of a chlorophyll a singlet state, however, the excited state P680* is created by recombination of a previously light-separated +/- CP, and not by absorption of a photon in the LHC. Those recombination PSII CP are stored and stabilised by activation energy barriers that help to increase photosynthetic efficiency. If the temperature of the sample is increased, there is some probability that the trapped charges can overcome the barrier of the activation energy and migrate back to the reaction center chlorophyll a where they undergo charge recombination. The energy released in the recombination is transferred back to the bulk chlorophyll and emitted as a thermoluminescence photon or converted into heat in a radiationless transition. Those stored "recombining" CP can be revealed by the so-called thermoluminescence bands, by alternating progressive warming, illumination, and dark periods. The emitted luminescence (thermoluminescence TL) is recorded during the "dark" intervals.

TERMOLUMINESCENCE is defined as the emission of light induced by heating of preilluminated materials. Luminescence emission increases with temperature (please, have a look at the Transition state Theory and specially, the Arrhenius-Eyring equation). Thus, the positive/negative CP are depleted by recombination.

The S states of the OEC, Pheophytin, QA and QB of PSII contribute to the generation of TL.

Prof. Demeter and Govindje wrote a nice minireview on thermoluminescence in plants, Article Thermoluminescence in plants

Article Thermoluminescence in plants

I hope this may help you.

Ronald

Dear Sagar S. Jagtap,

FLUORESCENCE: We can measure two types of fluorescence: prompt (PF) and delayed fluorescence (DF, also named luminescence). Both types are emitted from PSII.

PF results from deactivation/de-excitation of the lowest singlet excited states of chlorophyll a, within the photosynthetic unit (chlorophylls + light harvesting protein complexes LHC + reaction center P680 + oxygen evolving complex OEC). The quantum yield of PF depends on photochemical (PQ) and non-photochemical quenching (NPQ) processes.

PQ can be defined as the PSII capacity to trap photons energy into excitonic energy, resulting in a excited reaction center (P680*) generating positive and negative charge pairs CP.

In NPQ, the excitonic energy is transformed into heat (sink, radiative energy dissipation).

DF is the result of deactivation of a chlorophyll a singlet state, however, the excited state P680* is created by recombination of a previously light-separated +/- CP, and not by absorption of a photon in the LHC. Those recombination PSII CP are stored and stabilised by activation energy barriers that help to increase photosynthetic efficiency. If the temperature of the sample is increased, there is some probability that the trapped charges can overcome the barrier of the activation energy and migrate back to the reaction center chlorophyll a where they undergo charge recombination. The energy released in the recombination is transferred back to the bulk chlorophyll and emitted as a thermoluminescence photon or converted into heat in a radiationless transition. Those stored "recombining" CP can be revealed by the so-called thermoluminescence bands, by alternating progressive warming, illumination, and dark periods. The emitted luminescence (thermoluminescence TL) is recorded during the "dark" intervals.

TERMOLUMINESCENCE is defined as the emission of light induced by heating of preilluminated materials. Luminescence emission increases with temperature (please, have a look at the Transition state Theory and specially, the Arrhenius-Eyring equation). Thus, the positive/negative CP are depleted by recombination.

The S states of the OEC, Pheophytin, QA and QB of PSII contribute to the generation of TL.

Prof. Demeter and Govindje wrote a nice minireview on thermoluminescence in plants, Article Thermoluminescence in plants

Article Thermoluminescence in plants

I hope this may help you.

Ronald

Dear,

For solid state material samples such as radiation dosimeters

Fluorescence is the phenomenon of energy absorption by the electron can place it in an unstable excited state in which it will remain only a short time before falling back into the ground state by emitting a photon whose energy is equal the difference between excited and fundamental states.

Thermoluminescence (TL) refers to the process of stimulating, using thermal energy, the emission of luminescence from a substance following the absorption of energy from an external source by that substance. Where, luminescence is the physical phenomenon of light emission by the atoms or molecules of a material having absorbed a photon. This emission of light is more easily understood by a description of the electrons energetic state of the medium.

Ronald Maldonado Rodriguez wrote a comprehensive response.

So, thermoluminescence provides additional different information about photosynthetic activity of PSII ..right..?

Dear Sagar S. Jagtap ,

Absolutely yes. Let's say, fluorescence, both prompt PF and delayed DF, are complementary to thermoluminescence TL.

For example, a carefully planned experimental analysis of oscillating patterns in TL bands could tell you about the influence of temperature on the S state transitions at the WSC level. Moreover, TL indicates not only if there is an interruption of the electron transport chain, but it carries information about the specific blocking site location as well. I would say, better used them all of them and run them in parallel with other research techniques (as much as possible) to avoid misinterpretations. Please, read the Demeter and Govindjee Minireview paper.

Since the discovery of the Kautsky effect in 1931, an enormous research effort has been made to understand the biophysical mechanisms behind all these phenomena. Relatively not long ago, we just started to determine the crystallographic structure of photosynthetic protein complexes envolved in energy transduction in thylakoidal membranes. That is basic research so necessary to provide us with an understanding of the molecular mechanism of the processes related to photosynthesis. Once the whole molecular structure picture has been elucidated, then and only then, a real understanding will emerge. In the meanwhile, we can just be happy to have already some acceptable "good guesses" as theoretical frameworks guiding us in this field of research.

Thank you Prof. Ronald Rodriguez,

For very informative explanation of my query... It will really benefit me to proceed my research work.... ofcourse I will go through the Demeter and Govindjee Minireview paper...

I would be very happy to share my research with you in future...

Thanking you...