Chlorophyll fluorescence from Photosystem

Principle Chlorophyll fluorescence is a sensitive and early indicator of damage to photosynthesis and to the physiology of the plant resulting from the effect of allelochemicals, which directly or indirectly affects the function of photosystem II (Bolhar-Nordenkemf et ah, 1989, Krause and Weiss 1991). This approach is convenient for a photosynthesis analysis in situ and in vivo and quick detection of otherwise invisible leaf damage. The photosynthetic plant efficiency was measured using the method of induced chlorophyll fluorescence kinetics of photosystem II [Fo, non-variable fluorescence Fm, maximum fluorescence Fv=Fm-Fo, variable fluorescence t /2, half the time required to reach maximum fluorescence from Fo to Fm and photosynthetic efficiency Fv/Fm]. 

Humbeck K, Romer S and Senger H (1989) Evidence for an essential role of carotenoids in the assembly of an active photosystem 11. Planta 179 242-250 Hurry VM (1995) Non-photochemical quenching in xanthophyU cycle mutants of Arabidopsis and tobacco deficient in cytochrome B JF and ATPase activity. In Mathis P (ed) Photosynthesis From Light to Biosphere, pp 417-420. Kluwer Academic Publishers, Dordrecht Hurry V, Anderson JM, Chow WS and Osmond CB (1997) Accumulation of Zeaxanthin in absdsic acid-deficient mutants of Arabidopsis does not affect chlorophyll fluorescence quenching or sensitivity to photoinhibition in vivo. Plant Physiol 113 639-648... 

Chlorophyll a fluorescence induaion is a widespread method to evaluate the photosynthetic activity. This method is noninvasive, highly sensitive, fast, and easily measured. When chlorophyll molecules in photosystem II absorb light, that light may be assimilated into the hght reactions of photosynthesis or may be released as fluorescence or heat energy. In vivo fluorescence increases when photosynthesis declines or is inhibited. Numerous environmental f ors can affect the rate of electron transport between photosystem II and photosystem I due to interference with electron carriers between the two photosystems. For example, when the diuton is added in the measured sample, electron transport from photosystem II to photosystem I is blocked resulting in maximum fluorescence. This method was often employed to detect the photosynthetic activity of immobilized photosynthetic material. ... 

Chlorophyll Fluorescence. The variable fluorescence of photosystem II chlorophyll was monitored with an SF-20 Plant Productivity Fluorometer (Richard Brancker Research Ltd., Canada). The effect of herbicide treatments on the increase in fluorescence between the inflection (I) and peak (P) [as defined by the conventions of Mohanty and Govindjee 1) ] was determined from the tracings made on a strip chart recorder and expressed as a percent of the signal from untreated controls. Isolated chloroplasts were assayed in the resuspension buffer in a 1 cm fluorescence cuvette at a final concentration of 130 Xgs Chl/ml measurements were made with the probe placed directly against the surface of the cuvette. 

Barber, J. (1980). An explanation for the relationship between salt-induced thylakoid stacking and the chlorophyll fluorescence changes associated with changes in spillover of energy from photosystem II to photosystem I. FEBS Lett., 118 1-10. 

Chlorophyll fluorescence has been extensively utilized as an intrinsic membrane probe to study the photochemistry of photosynthesis. The assignment of the various fluorescence emission bands to specific functional complexes in the membrane has been attempted in many laboratories (Reviewed in Breton, 1982, Butler, 1979 Satoh, this symposium). Two chlorophyll fluorescence emission bands at 685 and 695 nm (at 77 K) have been identified to arise from photosystem II (PS II). In this paper we provide evidence for the fact that these two emission maxima arise from separate pigment-proteins within the PS II reaction center complex. 

Figure 3. Model for the structure of photosystem I, showing the distribution of chlorophyll a and b between the component chlorophyll-proteins. Excitation energy transfer may occur in a linear sequence from LHCII (under state 2) to CPI, The fluorescence emission peaks for the individual chlorophyll-proteins are also shown, although are usually shifted in vivo, when they are associated with other chlorophyll-proteins.

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