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