Evaluation of Sodium Exclusion from Different Tissues of Wheat (Triticum aestivum L.) Cultivars Differing in Salt Tolerance

A study of physiological responses of different wheat cultivars to saline conditions can lead to an identification of the main mechanisms in salt tolerance. Seven bread wheat cultivars differing in salt tolerance with varying ability of sodium accumulation in their different tissues were employed to assess ion distribution and sodium accumulation under saline conditions. Ion distribution and Na+, K+, as well as K+/Na+ ratio in different tissues including root, leaf-3 blade, flag leaf sheath and flag leaf blade at three salinity levels (0, 100 and 200 mM NaCl, with supplemental Ca2+), and also the effects of salinity on yield and dry biomass were assessed using a factorial experiment based on a randomized complete block design with three replications. Salt tolerance in wheat species was related to lower Na+ accumulation in leaves. Different ranges of sodium accumulation vs exclusion were detected in roots and shoots. Sodium contents reduced from root to shoot and were found more in old leaves’ blades than in young flag leaves. Flag leaf sheath was identified as the main tissue for Na+ sequestration. Salt tolerant cultivars sequestered higher Na+ concentrations specifically in root, old leaves and in leaf sheath. Moreover these cultivars maintained lower Na+ concentrations along with higher K+/Na+ ratios in flag leaf blade than in other tissues. Differences in ion partitioning and lower Na+ accumulation and also a maintenance of higher K+/Na+ ratios, specially in flag leaf, young growing and expanded organs, would appear to be the most important mechanisms contributing to the improved salt tolerance in different cultivars.