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 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 of D. salina declined, but the respiratory rate and in-tracellular ATP content increased in the dark. The F_(PS Ⅱ)/F_(PS Ⅰ) ratio at 77 K of D. salina 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. salina cells upon illumination. A decrease in LHC Ⅱ pho-sphorylation level was also observed when D. salina was exposed to hypoosmotic shock. Thus a state Ⅰ transition of photosynthetic apparatus occurs when D. salina 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, salina cells.