AVOIDANCE OF SODIUM ACCUMULATION IN THE SHOOT CONFERS TOLERANCE TO SALT STRESS IN CULTIVATED BARLEY

Growth and development of plants is adversely affected by ionic and osmotic stresses in the saline soil. Although barley (Hordeum vulgare) is regarded as relatively tolerant to salt stress among the Tririceae, modern barley cultivars suffer severely at salt concentrations encountered in the field constructed in reclaimed tidelands. This study was conducted to elucidate salt tolerance mechanisms of a collection from Tunisia (Tunisia 76; T76) at the germination and early seedling stages. Gwandongpi 41 (G41) Was used as a salt-susceptible control variety. Germination was examined in a culture solution containing 0, 150, 300, and 450 mM NaCl, respectively. Mineral content was analyzed for the three-week-old seedlings grown in 0 or 200 mM NaCl solutions for 0, 1, 3, and 5 days, respectively. Both varieties showed drastic differences in root and shoot growth at germination in saline conditions. T76 showed over 97% germination while G41 only 7% at 300 mM NaCl. The root and shoot growth at germination was negatively related to Na+ contents in the shoots. Sodium ion content was about three times higher in G41 than in T76 in the shoot of the seedlings treated for 5 days at 200 mM NaCl. The K+/Na+ ratio, which was mostly affected by Na+ content, was significantly higher in T76 than in G41. These results indicate that higher salt tolerance of T76 is conferred, at least in part, by the avoidance of salt accumulation in the shoot at high salt conditions.