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 t olerance were investigated with respect to growth, accumulation of Kand Na+ in the roots and the shoots, and Mg2+ and chlorophyll concentr ations in the leaves. Growth and K+ accumulation were stimulated by in termediate salinity in the known salt tolerant cultivars, Kharchia and Sakha-8, whereas these responses were less in the intermediate and se nsitive cultivars, Sakha-69 and T-79. At high salinity, the degradatio n of chlorophyll was somewhat lower in the salt tolerant than in the s ensitive cultivars and it coincided with a higher capability of the ma intenance of intracellular Mg2+ concentrations. Electron microscopic s tudies revealed that NaCl at 200 mM caused swelling of membranes in ch loroplasts of the sensitive cultivars while it had little effect in th e tolerant ones. Chlorophyll fluorescence measured in intact leaves sh owed that at 150-200 mM NaCl, the non-photochemical quenching decrease d 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 Ch la/Chlb ratio increased considerably more in the sensitive cultivars t han 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.