Comparative responses of wheat (Triticum aestivum L.) cultivars to salinity at the seedling stage

Seedling growth and ion content of Pakistani bread wheat cultivars was assessed in solution culture in the absence and presence of NaCl ( 100 and 200 mol m(-3)) to deter-mine whether seedling traits could be used in breeding programs for salt-tolerance. Growth was recorded as seedling fresh weight, and the shoot and leaves analysed for major inorganic ions. Plants subjected to salt stress excluded Na+ and Cl- ions from the shoot to varying extents. Exclusion preferentially maintained lower Na+ and Cl- levels in the apical tissue, as the leaf to leaf gradient in Na+ and C-l- became steeper as the external salinity increased, although there were significant differences between cultivars. Correlation analysis on individual plants indicated that excluding Na+ at low salinity, and Na+ and Cl- at high salinity, were correlated significantly with growth performance, although it was clear that other factors were also involved. The relationship of tolerance to ion exclusion was stronger when the data were examined on an individual plant basis than when related to pooled cultivar data or to the cultivar rank order derived from field trials, probably due to large variations in Na+, and to a lesser extent, Cl- transport in supposedly homozygous cultivars.