Copper Sulfate Mediated Alterations in Morphological Traits and Antioxidant levels of Tomato (Solanum lycopersicum L.) Subjected to Salinity Stress

Abstract

Salinity stress is one of the most severe abiotic constraints limiting tomato (Solanum lycopersicum L.) production worldwide. The present investigation was conducted to evaluate the influence of foliar CuSO₄ (copper sulfate) treatment on the growth and morpho-agronomic performance of tomato cv. Pant Tomato-3 under varying levels of NaCl-induced salinity stress. The experiment was laid out in a Completely Randomized Design (CRD) with three replications. Treatments comprised four salinity levels (S1: 25 mM, S2: 50 mM, S3: 100 mM NaCl and a non-saline control) and four CuSO₄ concentrations (M1:5 ppm, M2: 10 ppm, M3:50 ppm, M4:100 ppm). Key morphological parameters assessed included plant height, stem diameter, number of branches, number of leaves and days to 50% flowering. Results demonstrated that increasing NaCl concentrations significantly suppressed all vegetative growth parameters, with S3 (100 mM) recording maximum reductions in plant height (65 cm), stem diameter (3.9 mm) and number of branches (12) compared to the control. Salinity stress delayed days to 50% flowering, with S3 recording additional days (45) over the control (35). Salinity stress also triggered significant biochemical alterations, evidenced by enhanced accumulation of proline and elevated activities of antioxidant enzymes including superoxide dismutase (SOD) and catalase, reflecting activation of the plant defense system against oxidative stress. Application of CuSO₄, particularly at 50 ppm, moderated these stress-induced biochemical responses by maintaining comparatively balanced proline levels and antioxidant enzyme activities under mild to moderate salinity conditions. Application of CuSO₄ at 50 ppm proved most effective both as a standalone treatment and as a mitigation strategy under salinity stress, promoting plant height, stem diameter and number of branches, while partially restoring normal flowering phenology under mild to moderate stress. These findings suggest that CuSO₄ at 50 ppm holds promise as a growth-promoting and salinity-ameliorating agent in tomato cultivation, though its efficacy diminishes under severe stress conditions.