PHYSIOLOGICAL AND MORPHOLOGICAL RESPONSES OF GOSSYPIUM HIRSUTUM L. GENOTYPES TO COMBINED SOIL SALINITY AND CADMIUM STRESS DURING GERMINATION AND EARLY GROWTH STAGES

Abstract

Salinity and Cd are two important abiotic contaminants that affect cotton establishment and productivity, particularly during germination and early seedling development. The experiment was laid out as a 4 × 3 × 3 factorial design with four replicates, which comprised four Gossypium hirsutum L. genotypes (FH-142, CIM-602, MNH-886, and IUB-13) subjected to three levels of salinity (0, 75, and 150 mM NaCl) and three concentrations of Cd (0, 50, and 100 µM). Salinity and Cd stress also reduced the germination percentage, root length, shoot length, relative water content, seedling vigor, and increased electrolyte leakage, proline accumulation, malondialdehyde concentration, and Cd content in seedling tissues. The severity of the stress resulted in progressive reduction in germination percentage, root length, shoot length, relative water content, and seedling vigor, and an increase in electrolyte leakage, proline production, malondialdehyde concentration, and Cd content in seedling tissues. Root length, RWC, EL, and seedling vigor were significantly influenced by salinity, and Cd also had a significant effect on growth and physiological performance. There were significant genotype effects for several measured traits, indicating differential tolerance for the cotton genotypes evaluated. Significant interactions were observed between Genotype × Salinity, Genotype × Cd, and Salinity × Cd for relative water content, which suggests that combined stress conditions had a particular impact on plant water status. There was also a good negative correlation between relative water content and electrolyte leakage, which relates water loss from tissue to damage to the tissue's membranes. In general, simultaneous exposure to salinity and Cd had severe impacts on early establishment of cotton, which are related to growth, water relations, membrane integrity, and oxidative balance. The results showed that seedling vigor, root growth, relative water content, electrolyte leakage, proline content, and MDA were useful traits to evaluate cotton genotypes under combined abiotic stress.