Hypoosmotic shock induces a state I transition of photosynthetic apparatus in Dunaliella salina

摘要

The effects of hypoosmotic shock on state transition in darkness in Dunaliella sauna were studied. When the concentration of NaCl in culture medium was dropped from 1.5 to 0.5 mol/L abruptly, the photosynthetic rate of D. sauna declined, but the respiratory rate and intracellular ATP content increased in the dark. The F_(PS)~(II))/F_(PS)~I ratio at 77 K of D. sauna cells exposed to hypoosmotic shock was higher than that of control cells, indicating that more excitation energy was distributed to PS II in stressed D. sauna cells upon illumination. A decrease in LHC II phosphorylation level was also observed when D. saline was exposed to hypoosmotic shock. Thus a state I transition of photosynthetic apparatus occurs when D. saline suffers hypoosmotic shock in darkness, which is supposed to be related to an enhancement of respiration and an increase in ATP content in stressed D. saline cells.