EFFECTS OF ULTRAVIOLET-B RADIATION IN THE CO2 FIXATION, PHOTOSYSTEM-II ACTIVITY AND SPECTROSCOPIC PROPERTIES OF THE WILD AND MUTANT ANACYSTIS CELLS

Changes in photosystem II activity measured in wild and DCMU resistant mutant cells of Anacystis nidulans, after ultraviolet-B (UV-B) irradi ation were investigated. UV-B treatment of wild cells drastically decr eased PS II activity, while the mutant cells demonstrated certain degr ee of resistance to such damages. Decrease in the photosynthetic rate was found to be primarily due to the loss of energy transfer from phyc obilisoms (PBS) to chlorophyll (Chl) as the former in cyanobacteria ac ts as the primary light harvesting complex. This is supported by studi es of the absorption and fluorescence excitation and emission spectra.