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  • Author or Editor: Majid Azizi x
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The effects of NaCl stress on some growth parameters and ion accumulation in roots, shoots, and leaves of four fig genotypes (S × P, S × K, S × Sh, and S × 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·m−1. Salinity stress decreased growth parameters to a different extent in each genotype. Leaf water potential, stomatal conductance (g S), leaf number, shoot height, and root fresh weight were significantly decreased by salinity; and among the four fig genotypes studied, S × P and S × K were the most sensitive and the most tolerant genotypes, respectively. Furthermore, the highest reduction in shoot diameter and shoot fresh and dry weight were observed in S × Sh and the lowest reduction in S × K. Root dry weight decreased by increasing salinity, mainly in S × D. At S1 salinity treatment in both S × Sh and S × D genotypes, Na+ ion concentration was higher in leaves than in roots, but this pattern was not evident in S × P and S × 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 × D genotype that accumulated more Cl ion in leaves than in roots at S2 and S3 levels. These results indicate that the ability to sequester Na+ and Cl 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 Cl 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 × K is the most salt-tolerant genotype due to efficient exclusion of Na+ and Cl ions and lower reduction in growth factors.

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