The Role of Sorbitol in Improving Vegetative Growth and Some Physiological and Biochemical Traits of Cucumber (Cucumis sativus L.) under Salt Stress Conditions

Аннотация

The experiment was conducted during the 2025–2026 growing season in a plastic greenhouse in Al-Alam Subdistrict, Salah Al-Din Governorate, Iraq, to investigate the role of sorbitol in improving vegetative growth and some physiological and biochemical traits of cucumber (Cucumis sativus L.) under salt stress conditions. The experiment involved two factors: the first consisted of three salinity levels using sodium chloride (NaCl) at concentrations of 0, 3, and 6 mg L⁻¹, while the second consisted of three sorbitol levels at concentrations of 0, 2, and 4 mg L⁻¹, applied as foliar sprays. The experiment was conducted using a randomized complete block design (RCBD) in a factorial arrangement, with three replicates, comprising nine treatment combinations and 27 experimental units. The investigated traits included plant height, number of leaves, leaf area, fresh and dry weights, leaf chlorophyll, proline and soluble sugar contents, as well as the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) enzymes.

The results showed that increasing salinity levels reduced vegetative growth traits and chlorophyll content, whereas proline and soluble sugar contents and the activities of catalase and peroxidase increased with increasing salt stress. Sorbitol application improved vegetative growth traits and chlorophyll content, while reducing proline content compared with treatments receiving lower sorbitol concentrations. The S₀P₂ treatment (no salt addition with 4 mg L⁻¹ sorbitol) recorded the highest values for plant height, number of leaves, leaf area, fresh and dry weights, and chlorophyll content, reaching 90.16 cm, 19 leaves plant⁻¹, 1,390 cm² plant⁻¹, 200 g plant⁻¹, 28 g plant⁻¹, and 49 SPAD units, respectively. In contrast, the S₂P₀ treatment (6 mg L⁻¹ NaCl without sorbitol) recorded the lowest values for these traits, demonstrating the adverse effect of salinity on cucumber growth and the improvement associated with sorbitol application under the experimental conditions. The highest soluble sugar content and catalase and peroxidase activities were recorded in the S₂P₂ treatment, whereas the S₂P₀ treatment exhibited the highest proline content. Accordingly, it can be concluded that sorbitol at the highest concentration tested (4 mg L⁻¹) was associated with improvements in several indicators of vegetative growth and physiological status in cucumber under salt stress, although the response varied depending on the trait and salinity level.