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    STUDIA BIOLOGIA - Issue no. 2 / 2011  
         
  Article:   THE EFFECT OF ARGON-INDUCED ANAEROBIOSIS ON THE ACTIVITY OF PHOTOSYSTEM PS II IN SOME NOSTOCALES SPECIES.

Authors:  VICTOR BERCEA, ADRIANA BICA, BOGDAN DRUGĂ, COSMIN IONEL SICORA, NICOLAE DRAGOŞ. 		 
       
         
  Abstract:  The effects of atmospheric gases with anaerobiosis induction on the photosystem PS II activity at Nostoc linckia AICB 421 and Cylindrospermum alatosporum AICB 39 strains are related to the dynamics of the chlorophyll fluorescence and to the photosynthetic compounds, specific to each cyanobacterial strain. The minimal fluorescence (Fo) and maximal fluorescence (Fm) decreased in the first 60 min, followed by a slightly increase at the end of the argon treatment. The maximal quantum yield of the PS II (F/Fm) and the effective PS II quantum yield (YII) recorded a large variability. The quantum yield of nonregulated energy dissipation (YNO) was highly intense during the treatment. The high values of the coefficients of photochemical quenching qP and qL assess the oxidative redox state of the reaction centres PS II. The photochemical quenching and the quantum yield of the non-regulated energy recorded maximal values, which indicate that a poor photochemical conversion of the energy exists at the light-harvesting antenna complex. In DCMU presence, a poor energizing state was recorded, because all the reaction centres PS II are closed (reduced), resulting in a decrease of the variable fluorescence (Fv). In DCMU presence, the fluorescence rate is dependent of the functional size of the antenna PS II.

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