Changes of Photosystem Ⅱ Electron Transport in the ChlorophyⅡ-deficient Oilseed Rape Mutant Studied by ChlorophyⅡ Fluorescence and Thermoluminescence

The photosystem Ⅱ （PSII） complex of photosynthetic membranes comprises a number of chlorophyll-binding proteins that are important to the electron flow. Here we report that the chlorophyll b-deficient mutant has decreased the amount of light-harvesting complexes with an increased amount of some core polypeptldes of PSII, including CP43 and CP47. By means of chlorophyll fluorescence and thermolumlnescence, we found that the ratio of Fv/Fm, qP and electron transport rate in the chlorophyll b-deficient mutant was higher compared to the wild type. In the chlorophyll lPdeflclent mutant, the decay of the primary electron acceptor quinones （QA-） reoxidation was decreased, measured by the fluorescence. Furthermore, the thermoluminescence studies in the chlorophyll bdeficient mutant showed that the B band （S2/S3QB-） decreased slightly and shifted up towards higher temperatures. In the presence of dlchlorophenyl-dlmethylurea, which is inhibited in the electron flow to the second electron acceptor quinines （QB） at the PSll acceptor side, the maximum of the Q band （S2QA-） was decreased slightly and shifted down to lower temperatures, compared to the wild type. Thus, the electron flow within PSll of the chlorophyⅡ b-deficient mutant was down-regulated and characterized by faster oxidation of the primary electron acceptor quinine QA-via forward electron flow and slower reduction of the oxidation S states.

Changes of Photosystem II Electron Transport in the Chlorophyll-deficient Oilseed Rape Mutant Studied by Chlorophyll Fluorescence and Thermoluminescence

The photosystem II (PSII) complex of photosynthetic membranes comprises a number of chlorophyll‐binding proteins that are important to the electron flow. Here we report that the chlorophyll b‐deficient mutant has decreased the amount of light‐harvesting complexes with an increased amount of some core polypeptides of PSII, including CP43 and CP47. By means of chlorophyll fluorescence and thermoluminescence, we found that the ratio of Fv/Fm, qP and electron transport rate in the chlorophyll b‐deficient mutant was higher compared to the wild type. In the chlorophyll b‐deficient mutant, the decay of the primary electron acceptor quinones (Q_A^?) reoxidation was decreased, measured by the fluorescence. Furthermore, the thermoluminescence studies in the chlorophyll b‐deficient mutant showed that the B band (S₂/S₃Q_B^?) decreased slightly and shifted up towards higher temperatures. In the presence of dichlorophenyl‐dimethylurea, which is inhibited in the electron flow to the second electron acceptor quinines (Q_B) at the PSII acceptor side, the maximum of the Q band (S₂Q_A^?) was decreased slightly and shifted down to lower temperatures, compared to the wild type. Thus, the electron flow within PSII of the chlorophyll b‐deficient mutant was down‐regulated and characterized by faster oxidation of the primary electron acceptor quinine Q_A^? via forward electron flow and slower reduction of the oxidation S states. (Handling editor: Li‐Xin Zhang)