EFFECTS OF NACL SALINITY ON GROWTH, CATION ACCUMULATION, CHLOROPLAST STRUCTURE AND FUNCTION IN WHEAT CULTIVARS DIFFERING IN SAIL TOLERANCE

The effects of salinity on four cultivars of wheat differing in salt tolerance were investigated with respect to growth, accumulation of K+ and Na+ in the roots and the shoots, and Mg2+ and chlorophyll concentrations in the leaves. Growth and K+ accumulation were stimulated by intermediate salinity in the known salt tolerant cultivars, Kharchia and Sakha-8, whereas these responses were less in the intermediate and sensitive cultivars, Sakha-69 and T-79. At high salinity, the degradation of chlorophyll was somewhat lower in the salt tolerant than in the sensitive cultivars and it coincided with a higher capability of the maintenance of intracellular Mg2+ concentrations. Electron microscopic studies revealed that NaCl at 200 mM caused swelling of membranes in chloroplasts of the sensitive cultivars while it had little effect in the tolerant ones. Chlorophyll fluorescence measured in intact leaves showed that at 150-200 mM NaCl, the non-photochemical quenching decreased considerably in the sensitive T-79 but not in the tolerant Kharchia. The relaxation patterns of the non-photochemical quenching have also shown differences between the tolerant and sensitive cultivars. The Chla/Chlb ratio increased considerably more in the sensitive cultivars than in the tolerant ones. These results suggest that the chloroplasts under saline conditions in the leaves of salt tolerant wheat cultivars, are not exposed to excess Na+, in contrast to those in the sensitive ones.