Effect of NaCl on chlorophyll fluorescence and thylakoid membrane proteins in leaves of salt sensitive and tolerant rice (Oryza sativ L) varieties

In this study we compare a few physiological parameters of a salt sensitive (Jaya) and salt resistant (Korgut) rice varieties to understand mechanism of salt tolerance. Jaya, high yielding salt-sensitive rice (Oryza sativa) variety, and Korgut, a 100% salt-tolerant rice variety, were grown for 15 days in vermiculite irrigated with NaCl solutions of 0 – 200 mmolL-1 prepared in Hoagland's solution (pH 6.5). It was observed that initial fluorescence (F0) value increased, and the maximal fluorescence ratio (Fm) decreased in Jaya; however, the Korgut variety maintains the F0 and Fm value without much significant variation as NaCl increased. On the other hand, Actual efficiency (О¦PSII) significantly decreased in Jaya showed slightly decreased at 200 mmolL-1 NaCl treatment. The polypeptide composition of the thylakoid membrane decreases after NaCl treatment in the Jaya variety, but it's maintained in the Korgut variety. Photo-inactivation of PSII in Jaya includes the loss of the D1 and D2, (32-34 kDa) protein, probably from greater photosynthetic damage caused by salinity stress; Korgut is not showing alternation of the same protein, and it's maintained the greater photosynthetic. In Jaya, most prominently, the dramatic decline of the 47-kDa chlorophyll protein (CP), 17-kDa (F0), and (10kDa) OEC protein vice versa in Korgut. The decreased in 47-kDa, and 23kDa proteins in Jaya lead to the decreased energy transfer from the light-harvesting antenna to PSII due to the marked alterations in the composition of thylakoid membrane proteins. The most important of changes in Korgut indicate maintained chlorophyll fluoresces without altering the thylakoid membrane protein towards adaptation to salinity. These findings can be translated into efforts to develop more salt-tolerant cultivars and exhaust the possibilities of using saline soils.