Abstract
We investigated the cause of swelling of thylakoids under salinity to elucidate the mechanism of salt-induced damages in chloroplasts. Because salt stress has both ionic and osmotic effects, we separately investigated ionic and osmotic effects of salinity on the ultrastructure of chloroplasts in salt-treated rice seedlings. NaCl induced swelling of thylakoids, however, PEG did not induce the swelling, both at a water potential of -1.0 MPa. When plants were desiccated by withholding water for 2 weeks or by reducing water supply for 1 month on soil culture, thylakoids did not swell. It is suggested that the swelling of thylakoids under salinity is induced by ionic effects but not osmotic effects. Because the swelling of thylakoids is the typical phenomenon of oxidative stress, it is also suggested that salt-induced oxidative stress could be induced by ionic effects.
