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    STUDIA BIOLOGIA - Issue no. 2 / 2004  
         
  Article:   ORGANIZAREA MEMBRANELOR TILACOIDALE ŞI FUNCŢIONAREA LOR SUB INFLUENŢA STRESULUI FOTIC.

Authors:  ANCA BUTIUC-KEUL, LASZLO FODORPATAKI, CONSTANTIN DELIU.
 
       
         
  Abstract:  Thylakoid Membrane Organization and Functioning under High Light Stress. Several experiments regarding the organization of thylakoid membranes and their functioning under high light stress were carried out. As shown by circular dichroism spectra (CD) the light-harvesting pigment-protein complexes of 3 weeks old pea plantlets are better organized than the ones of 6 weeks old pea plantlets, fact that could confer high capacity to young plantlets to undergo reversible changes of thylakoid membrane organization under high light intensity. Under 120ĺ exposure to high light the amplitude of CD spectrum is decreased by 50% compared to CD spectrum of control chloroplasts. The fluorescence parameters give important informations about thylakoid membrane organization and functioning under stress conditions. The initial fluorescence (F0) shows that light-harvesting complexes have lower extension under high light intensity. The values of temporary, maximal fluorescence (Fm) are more reduced than F0 values under 600 and 1200 Ámol m-2s-1 light intensity. The Fv/Fm ratio as an indicator of potential quantum efficiency of photosynthesis, shows the highest value at low light intensity while under a light intensity of 600-1200 Ámol m-2s-1, the values of Fv/Fm ratio are strongly decreased.  
         
     
         
         
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