Spermidine mitigates salt stress in grapevine with alterations in physicochemical properties and nutrient composition

Abstract Background Polyamines are plant growth regulators that exert a pivotal role in salt tolerance. Aims This research focused on investigating the effect of spermidine on morphological and physicochemical characteristics and ion accumulation of two grapevine cultivars under NaCl stress. Methods A greenhouse experiment was conducted with three factors, including two grapevine cultivars ( Vitis vinifera L. cv. Bidaneh‐Sefid and cv. Siah‐Sardasht), four levels of NaCl (together with the nutrient solution, including 0 [control], 20, 40, and 80 mM), and four spermidine levels ([foliar spray], 0 [control], 0.25, 0.5, and 1 mM). The experiment was performed in a factorial trial in accordance with a randomized complete design with three replicates. Results Vegetative growth indices, including leaf number, fresh and dry weight of shoot, and root, were decreased by NaCl treatments. The application of spermidine positively reduced the effects of NaCl on morphological characteristics. Moreover, NaCl and/or spermidine significantly ( p ≤ 0.05) improved antioxidant enzyme activities associated with rising total protein accumulation. NaCl stress significantly decreased ion percentage (calcium, magnesium, phosphate, potassium, iron, and zinc) in the leaves of both cultivars. Based on the results, increasing salinity levels significantly boosted plant Na + and Cl − percentage, along with increased membrane permeability and malondialdehyde (MDA) concentration. Interestingly, cv. Bidaneh‐Sefid leaves accumulated less Na + and Cl − compared to the other cultivar. On the other hand, applying spermidine reduced the levels of Na + and Cl − in both cultivars, and this reduction was associated with a decrease in membrane permeability and MDA concentration. Conclusions The findings confirmed the role of spermidine in reducing the negative effects of NaCl, although more investigations with different grapevine cultivars under NaCl stress are required.