Effects of Different Levels of Water Salinity on Plant Growth, Biochemical Content, and Photosynthetic Activity in Cabbage Seedling Under Water-Deficit Conditions

Salinity and drought are the major abiotic stress factors that threaten the sustainability of agricultural production, particularly in semi-arid regions. Therefore, in such regions, it becomes imperative to determine the effects of salinity under deficit irrigation conditions. In this context, the present study evaluated the effects of five different levels of irrigation water salinity (S1, 0.3 dS/m-control; S2, 2.5 dS/m; S3, 5.0 dS/m; S4, 7.5 dS/m, and S5, 10.0 dS/m) on plant growth, biochemical content, and photosynthetic activity in cabbage seedling under three levels of irrigation (full irrigation, I100; 25% water deficit, I75; 50% water deficit, I50). The results revealed that both saline water and water deficit caused significant losses in the evaluated plant growth parameters. In addition, both stress factors were observed to significantly increase the levels of malondialdehyde (MDA), proline (PR), protein (PT), hydrogen peroxide (H2O2), and membrane damage in cabbage. The activities of the stress-related enzymes catalase (CAT) and peroxidase (POX) were also increased significantly in the plants subjected to both stresses. In addition, both irrigation salinity and water stress decreased the stomatal conductivity (GSW) and chlorophyll fluorescence (Fv/Fm), with the values reaching up to 72% and 82%, respectively. The plants in the S1I100, S1I75, and S2I100 treatments presented the best results in terms of plant growth parameters and photosynthetic activity. Finally, it was revealed that a 25% water deficit and irrigation water with an electrical conductivity (EC) of over 2.5 dS/m would cause adverse effects on the cabbage plants cultivated in arid and semi-arid regions.