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  • Author or Editor: Ali Tehranifar 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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The aim of this study was to compare the effects of foliar fertilization with a nitrogen (N) fertilizer containing nanoparticles (nN) with those of foliar fertilization with urea on the characteristics of pomegranate fruits cv. Ardestani. The experiment was carried out using a completely randomized block design with five treatments and four replications (trees) per treatment during two consecutive years, 2014 and 2015. Two foliar applications of nN (0.25 and 0.50 g N/L, equivalent to ≈1.3 and 2.7 g N/tree or 0.9 and 1.8 kg N/ha; nN1 and nN2, respectively) and urea (4.6 and 9.2 g N/L, equivalent to ≈24.4 and 48.8 g N/tree or 16.3 and 32.5 kg N/ha; U1 and U2, respectively) were applied at full bloom and 1 month later, and trees not treated with any N fertilizer were used as a control. Results show that foliar N fertilization increased fruit yield (by 17% to 44%) and number of fruits per tree (by 15% to 38%). The highest fruit yields (17.8 and 21.9 kg/tree) and number of fruits per tree (62.8 and 70.1/tree) were obtained with the treatment nN2 (1.8 kg N/ha), whereas the lowest fruit yields (12.4 and 16.2 kg/tree) and number of fruits per tree (45.5 and 55.3/tree) were recorded in the control trees. The treatments U1 and nN2 increased fruit length (the latter only in the second season), whereas the treatment U1 increased average fruit weight (10% to 11%). The treatment nN2 increased aril juice and total soluble solids (TSS) in both seasons and titratable acidity (TA) only in the first one, whereas the treatment U1 increased TSS in both seasons and aril juice and TA in the second season. Treatments nN2 and U1 also increased total sugars and decreased total anthocyanins. On the other hand, fruit diameter, fruit cracking, peel thickness, aril content, weight of 100 arils, juice pH, maturity index, antioxidant activity, and total phenolic compounds were unaffected by N fertilization. Nitrogen fertilization increased the leaf concentration of N, whereas the leaf concentrations of P, K, Mn, and Zn were unaffected. Results indicate that pomegranate fruit yield was improved similarly with two applications (at full bloom and one month later) of nN fertilizer at a rate of 1.8 kg N/ha and with two applications of urea at a rate of 16.3 kg N/ha. Furthermore, fruit quality was improved more with the nN fertilizer at a rate of 1.8 kg N/ha than with two applications of urea at a rate of 16.3 kg N/ha.

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