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    STUDIA BIOLOGIA - Issue no. 2 / 2011  
         
  Article:   THE PHOTOCHEMICAL PS II ACTIVITY IN CYANOBACTERIAL STRAINS BELONGING TO THE NOSTOCALES GROUP IN ANAEROBIOSIS CONDITIONS.

Authors:  VICTOR BERCEA, CRISTIAN COMAN, COSMIN IONEL SICORA, NICOLAE DRAGOŞ. 		 
       
         
  Abstract:  The effect of anaerobiosis on the fluorescence in Anabaenopsis sp. AICB 717 and Aphanizomenon elenkinii AICB 709 strains was investigated. Chlorophyll a, carotenoids and phycobiliproteins, identified based on their absobtion spectrum, showed no significant alterations in anaerobiosis conditions. The minimal (F0) and maximal (Fm) fluorescence yield, decreased in the first 60 min of anaerobiosis, followed by a light increase at the end of the argon treatment. The PS II reaction centers’ oxidation/reduction state dropped in intensity in the first moments of anaerobiosis. The PS II maximal quantum yield (F/Fm) and the effective quantum yield (Y(II)) showed an increased variability reported to the strain investigated. The photochemical coefficients qP and qL had a similar growth, their value being close to 1, this showing the oxidative redox state of the PS II reaction centers. The photochemical quenching and the quantum yield of nonregulated energy dissipation are at their mximum, designating the fact that there is a weak photochemical conversion of energy caused by the light absorption antenna complex. In the presence of DCMU a weak energization state was recorded, leading to relatively equal F0 and Fm values caused by the fact that all the PS II reaction centers become closed (reduced) causing a decrease of fluorescence.

Keywords: chlorophyll fluorescence; DCMU inhibitor; photochemical activity; photosystem PS II and PS I; photochemical quenching. 		 
         
     
         
         
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