The study of the primary photoprocesses in Photosystem I of chloroplasts Recombination luminescence,chlorophyll triplet state and triplet-triplet annihilation |
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Authors: | VA Shuvalov |
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Institution: | Institute of Photosynthesis, U.S.S.R. Academy of Sciences, Pushchino, Moscow reg. U.S.S.R. |
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Abstract: | The dependence of the delayed luminescence of Photosystem I on the state of the reaction centers has been studied. Light flash induces a charge separation in the centers: . Dark recombination of charges is accompanied by the recombination luminescence with .If the centers are in the P-700 · P-430? state or if P-430 is inactivated by heat, then flashing of Photosystem I generates the triplet state chlorophyll with . The triplet state has been measured by the delayed fluorescence of chlorophyll at 20 °C and 77 °K and by the chlorophyll phosphorescence at 77 °K. The delayed fluorescence at 20 °C arises from the thermal activation of the triplet state up to the excited singlet level of chlorophyll and at 77 °K it is due to triplet-triplet annihilation. The quantum yield of the triplet formation, estimated by a comparison of the light saturation curves of delayed fluorescence at 20 °C and of P-700 photooxidation under the same experimental (optical) conditions, is ≈ 0.9 of the P-700+ yield. Only one triplet of chlorophyll can be generated per P-700. Under heat inactivation of P-430 the triplet formation is not observed when P-700 is oxidized.It is assumed that the triplet-triplet annihilation at 77 °K is related with the strong interaction between the chlorophyll molecules in the pigment complex of Photosystem I. The possibility of a triplet participation in the primary processes of photosynthesis is discussed. |
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