Abstract:Abstract— The origin of glow peaks (thermoluminescence) was investigated in isolated spinach chloroplasts and Euglena cells by pretreatment with various concentrations of 3‐(3,4 dichlorophenyl)‐1,1‐dimethylurea (DCMU)†, different light intensities, and after mild heating at various temperatures. Experiments are also reported on subchloroplast fractions enriched in pigment systems I (PSI) or II (PSII) (prepared under conditions to reduce destruction of membranes by excessive detergent contact).
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“…This finding has been further corroborated by subsequent experimentation by several workers using bundle sheath chloroplasts of C-4 plants that apparently lack PSII and, therefore, show very weak TL. The inhibition of PSI activity by HgCl 2 does not affect the glow peak yield of isolated chloroplast (Sane et al, 1977;Horvath et al, 1978). Several other studies using herbicides and inhibitors that interact with PSI electron flow supports this conclusion.…”
Section: Historical Perspectivesupporting
confidence: 68%
“…Major TL bands are missing in etiolated leaves. Intermittent illumination to greening leaves which does not develop Mn clusture properly do not show the TL bands (Inoue et al, 1976;Sane et al, 1977). Misra et al (1998b) reported a gradual increase in the Q and B band from base to apex of that wheat leaves greening under continuous illumination, which confirms a developmental gradient across the wheat leaf lamina and a gradual development and organization of the photosynthetic PSII complexes.…”
Section: Stress Induced Changes In Tl Glow Peaksmentioning
“…This finding has been further corroborated by subsequent experimentation by several workers using bundle sheath chloroplasts of C-4 plants that apparently lack PSII and, therefore, show very weak TL. The inhibition of PSI activity by HgCl 2 does not affect the glow peak yield of isolated chloroplast (Sane et al, 1977;Horvath et al, 1978). Several other studies using herbicides and inhibitors that interact with PSI electron flow supports this conclusion.…”
Section: Historical Perspectivesupporting
confidence: 68%
“…Major TL bands are missing in etiolated leaves. Intermittent illumination to greening leaves which does not develop Mn clusture properly do not show the TL bands (Inoue et al, 1976;Sane et al, 1977). Misra et al (1998b) reported a gradual increase in the Q and B band from base to apex of that wheat leaves greening under continuous illumination, which confirms a developmental gradient across the wheat leaf lamina and a gradual development and organization of the photosynthetic PSII complexes.…”
Section: Stress Induced Changes In Tl Glow Peaksmentioning
“…Light emission can be obtained from preilluminated samples by slow heating [the glow curve technique (Arnold and Sherwood, 1957;Arnold and Azzi, 1968) with four or more bursts of emission at different temperatures (Shuvalov and Litvin, 1969;Arnold and Azzi, 1971;Desai et al, 1975;Sane et al, 1977)l. Rapid heating (temperature-jump) also causes preilluminated chloroplasts to emit a pulse of delayed light ; Jursinic and Govindjee, 1972;Malkin and Hardt, 1973).…”
Abstract-The delayed light emission decay rate (up to 120~s) and the rise in chlorophyll a fluorescence yield (from 3 to 35 ys) in isolated chloroplasts from several species, following a saturating 10 ns flash, are temperature independent in the CL35"C range. However, delayed light in the 120-340ps range is temperature dependent. Arrhenius plots of the exponential decay constants are: (a) linear for lettuce and pea chloroplasts but discontinuous for bush bean (12-17°C) and spinach (12-20°C) chloroplasts; (b) unaffected by 3-(3,4 dich1orophenyl)l ,1-dimethylurea (inhibitor of electron flow), gramicidin D (which eliminates light-induced membrane potential) and glutaraldehyde fixation (which stops gross structural changes).The discontinuities, noted above for bush bean and spinach chloroplasts, are correlated with abrupt changes in (a) the thylakoid membrane lipid fluidity (monitored by EPR spectra of 12 nixtroxide stearate, 12 NS) and (b) the fluidity of extracted lipids (monitored by differential calorimetry and EPR spectra of 12 NS). However, no such discontinuity was observed in (a) chlorophyll a fluorescence intensity of thylakoids and (b) fluorescence of tryptophan residues of delipidated chloroplasts.Microsecond delayed light is linearly dependent on light intensity at flash intensities as low as one quantum per 2 x lo4 chlorophyll molecules. We suggest that this delayed light could originate from a one quantum process in agreement with the hypothesis that recombination of primary charges leads to this light emission. A working hypothesis for the energy levels of Photosystem I1 componcnts is proposed involving a charge stabilization step on the primary acceptor side, which is in a lipid environment.Finally, the redox potential of P680 (the reaction center for chlorophyll of system 11) is calculated to he close to 1.&1.3V.
“…Transformation of the B-band to Q-band occurs due to inhibition of electron transfer between Q A and Q B by DCMU, which enables the stabilization of Q A − as a negative charge detectable by TL instead of Q B − . Appearance of the Qband requires a functional water-splitting complex (40). Figure 2B shows the TL glow curves observed when 15 μM DCMU was added in control and RR-treated thylakoids.…”
Ruthenium red (RR) is known to be an inhibitor that binds to Ca2+ sites. It releases Ca2+ and Cl(-) together with the extrinsic polypeptide of 17 kDa associated with the oxygen evolving complex of photosystem II. In this work we used thermoluminescence to study S2/3QB(-) and S2QA(-) charge recombination. It is shown that RR produced a deeper inhibition of oxygen evolution compared with the effect of extrinsic polypeptide or Ca2+/Cl(-) depletion. Even though Mn is not released, the Mn cluster is disorganized by RR and the S1-->S2 transition is inhibited.
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