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Response of the photosynthetic apparatus of Dunaliella salina to sublethal concentrations of the herbicide 3-(3´,4´-dichlorophenyl)-1,1-dimethyl urea.

Autoři: Nauš J., Melis A.Publikováno : Photosynthetica 26(1), 67-78Rok: 1992

The composition and function of the photosynthetic apparatus in Dunaliella salina was studied upon cell acclimation to sublethal concentrations of the herbicide 3-(3',4'-dichlorophenyl)-1,1- dimethyl urea (DCMU). In the concentration range of 0-100 nM DCMU, chlorophyll (Chl) content per cell increased, whereas the Chl a/b ratio and the cell growth rate decreased progressively with the herbicide concentration. The photosystem (PS) composition and the Chl antenna size in the thylakoid membrane also changed. Progressive with the concentration of DCMU in the cell growth medium, the PS1/Chl ratio decreased, whereas the PS2/Chl ratio remained fairly constant. The changes resulted in a higher PS2/PS1 ratio in the thylakoid membranes. Concomitantly, the functional Chl antenna size of PS2 was increased whereas that of PSI slightly decreased. When grown in the presence of DCMU, D. salina thylakoids contained a significantly greater proportion of PS2 centers inactive in the QA-QB electron-transfer reaction (QB-nonreducing centers). These modifications were more evident in older than in younger cultures.

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