The effects of NaCl stress on some growth parameters and ion accumulation in roots, shoots, and leaves of four fig genotypes (S 3 P, S 3 K, S 3 Sh, and S 3 D) were investigated. Eight-month-old fig plants growing in a mixture of sand, leaf mold, and clay (1:1:1) were irrigated with solutions containing NaCl at various levels: 0.6 (S0), 4 (S1), 6 (S2), and 8 (S3) dS·mL1. Salinity stress decreased growth parameters to a different extent in each genotype. Leaf water potential, stomatal conductance (gS), leaf number, shoot height, and root fresh weight were significantly decreased by salinity; and among the four fig genotypes studied, S 3 P and S 3 K were the most sensitive and the most tolerant genotypes, espectively. Furthermore, the highest reduction in shoot diameter and shoot fresh and dry weight were observed in S3Sh and the lowest reduction in S3K. Root dry weight decreased by increasing salinity, mainly in S3D. At S1 salinity treatment in both S3Sh and S3D genotypes, Na+ ion concentration was higher in leaves than in roots, but this pattern was not evident in S 3 P and S 3 K genotypes in NaCl treatments below S2 and S3, respectively. Chloride concentrations in all organs increased and were higher in roots than in both leaves and shoots, except in S 3 D genotype that accumulated more ClL ion in leaves than in roots at S2 and S3 levels. These results indicate that the ability to sequester Na+ and ClL ions in roots differs among the genotypes used in this study. Overall, results indicated that salinity tolerance in fig tree is strongly associated with Na+ and ClL ions exclusion mechanism from shoots. Moreover, to our surprise, salinity stress considerably increased K+ ion concentration in leaves and shoots of salt-sensitive genotypes. Our proposed explanation is that the inability of salt-sensitive fig genotypes to prevent delivery of hazardous ions to shoot is compensated by tissue tolerance mechanism. Keeping high cytosolic K+ ion may lead to better sequestration of Na+ ion in vacuoles and, therefore, enable the genotypes with poor Na+ exclusion mechanism to handle large amounts of Na+ ion in leaves. Finally, S 3 K is the most salt-tolerant genotype due to efficient exclusion of Na+ and ClL ions and lower reduction in growth factors.

Keywords