Background: Soil salinity is a real challenge in nowadays crop production in many regions. Various strategies have been applied to increase plant salinity tolerance. Salicylic acid (SA) frequently has been reported to increase plant salinity tolerance; however, the comparative efficiency of soil (root) or foliar application of SA has not been well tested yet. In this study, the effects of root or leaf pretreatment, and leaf treatment with 100 mg L −1 salicylic acid were evaluated on growth characteristics of tomato seedlings (Solanum lycopersicum Mill) under salinity stress. The plants were grown 3 weeks in sand that were fed with Hoagland nutrient solution with or without 100 mM NaCl. Results: The results showed that salinity significantly reduced tomato seedling growth and traits of plant height, leaf area, shoot fresh weight, and nutrient concentration of potassium, calcium, iron and zinc compared to control plants. However, leaf SPAD value, root fresh and dry weights, leaf concentration of sodium, proline and soluble sugars were significantly increased under 100 mM NaCl salinity compared to control plants. Application of salicylic acid particularly by foliar pretreatment increased the tomato plant growth and those traits that were reduced by NaCl salinity. Application of SA, particularly foliar pretreatment, also increased the root fresh and dry weights, leaf proline and soluble sugars concentrations as compared with salinity alone. Foliar SA pretreatment significantly increased leaf K and Fe concentrations, whereas leaf Ca was significantly increased by either root or leaf pretreatment with SA under salinity. Conclusion: The results indicate that the most to least effective method of SA application was leaf pretreatment, root pretreatment and leaf treatment, respectively, to recover the reduced growth parameters of tomato plant under salinity stress.

A nutrient solution experiment was performed to evaluate the growth, yield and fruit biochemical characteristics of strawberry under different potassium levels of nutrient solution. Potassium concentrations including 235 (control), 350, 450 and 600 mg L-1 were applied to three strawberry genotypes of Camarosa, Selva and Parus under hydroponic culture. In the three genotypes, the maximum leaf area was observed at 350 mg L-1 K, and the maximum shoot fresh weight was either at 350 mg L-1 (in Camarosa and Parus) or at 400 mg L-1 (in Selva). In Selva, higher yield was produced by higher K concentrations than control (17-33%) and in Camarosa, the maximum yield was produced at 350 mg L-1 (16%), whereas fruit yield in Parus was not affected by K concentrations. In Selva and Parus application of 350 mg L-1 potassium produced more fruits than control. The maximum fruit vitamin C content in Camarosa and Selva was at 350 mg L-1, and in Parus at 450 mg L-1, while the significant lowest in three genotypes was at 600 mg L-1. Fruit titratable acidity and pH in Camarosa and Selva, and fruit TSS in Parus were not affected by K levels. Fruit total soluble solids (TSS) in Camarosa and Selva were maximum in 350 and 450 mg L-1. Increasing K concentrations of nutrient solution increased leaf and fruit K concentration than control. The results indicate that overall plant growth and fruit quality of three strawberry genotypes were increased by 350 mg L-1 potassium, while application of 600 mg L-1 reduced most traits than control. The Selva genotype had also a better response to higher concentration of K than two other genotypes.

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