Action spectra for photo reaction i and photo reaction ii of photosynthesis in the blue green alga anacystis nidulans
Wang, R.T.; Stevens, C.L.R.; Myers, J.
Photochemistry and Photobiology 25(1): 103-108
ISSN/ISBN: 0031-8655 Accession: 004661459
Action spectra for photoreactions I and II of photosynthesis were obtained for A. nidulans and 3 of its variants which had altered chlorophyll/phycocyanin ratios. The spectra are properly scaled to each other. They provide information on contributions of phycocyanin and chlorophyll to initial absorption and final distribution of excitation energy to reaction centers I and II. In normally pigmented cells the light harvesting pigments for photoreaction I include about 40% of the phycocyanin and 84% of the chlorophyll. Both in normal cells and in cells with altered pigmentation excitation energy from phycocyanin is delivered to photoreaction II via a small number of chlorophylls. In response to alterations in chlorophyll/phycocyanin ratio action I spectra showed large variations, whereas action II spectra were essentially invariant. Apparently alteration in chlorophyll components in Anacystis is attended by a special restriction: there are only small changes in the amount of chlorophyll accessible to photoreaction II in the face of large changes in the amount committed to photoreaction I.