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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: The effect of various light intensities on PS II photochemistry and xanthophyll cycle and also their recovery in the dark are presented. The green alga Mougeotia sp., strain AICB 560 displayed a slower growth. Under 1500�mol.m-2.s-1 light the fluorescence has been enhanced the first 60 minutes, especially FV, and then has decreased according to the exposure time. The quantic efficiency and PS II quantic yield were equal to the control. Chlorophyll a has decreased, chlorophyll b has enhanced and the high content of anteraxanthin, lutein and carotens was highlighted. The presence of zeaxanthin proves the operation of the xanthophyll cycle. It becomes functional the lutein → lutein 5.6-epoxide interconvertibilily with photoprotective role. The 3000 �mol.m-2.s-1 light caused the increase of F0, the decrease of FM, FV and FV/FM, certifying the installation of photoinhibition. The level of zeaxanthin and anteraxanthin has grown, and this certifies the increasing of the excess excitation energy dissipation. The photochemical activity has dramatically decreased by exposure to 4500 �mol.m-2.s-1. The xanthophylls of the xanthophyll cycle were maintained at high values, as well as the protein content. The recovery of the photochemical activity was more obvious in those variants treated with the first two lights, and it has a bimodal graphic shape. The level of violaxanthin increased by the epoxidation of zeaxanthin, whose concentration has decreased, as well as the anteraxanthin concentration. It was proved the PS II damage irreversibility in dark |
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