Early stage toxicity of excess copper to photosystem II of Chlorellapyrenoidosa–OJIP chlorophyll a fluorescence analysis
XIA Jianrong , TIAN Qiran
DOI:
Received December 11, 2008,Revised March 20, 2009, Accepted , Available online
Volume 21,2009,Pages 1569-1574
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Acute toxicity of excess Cu on the photosynthetic performance of Chlorella pyrenoidosa was examined by using chlorophyll a
fluorescence transients and JIP-test after exposure to elevated Cu concentrations for a short time period. High Cu concentration resulted
in a significant suppression in photosynthesis and respiration. The absorption flux (ABS/RC) per PSII reaction center increased with
increasing Cu concentration, but the electron transport flux (ET0/RC) decreased. Excess Cu had an insignificant e ect on the trapping
flux (TR0/RC). The decline in the e ciency, with which a trapped exciton can move an electron into the electron transport chain
further than QA?? ( 0), the maximal quantum yield of primary photochemistry ('P0 ), and the quantum yield of electron transport ('E0 )
were also observed. The amount of active PSII reaction centers per excited cross section (RC/CS) was also in consistency with the
change of photosynthesis when cells were exposed to excess Cu concentration. JIP-test parameters had a good linear relationship with
photosynthetic O2 evolution. These results suggested that the decrease of photosynthesis in exposure to excess Cu may be a result of
the inactivation of PSII reaction centers and the inhibition of electron transport in the acceptor side.
