Copper Effects on Growth, Lipid Peroxidation, and Total ‎Phenolic Content of Rosemary Leaves under Salinity Stress

Plant growth is often limited by low levels of soil micronutrients such as copper (Cu), ‎especially in calcareous salt-affected soils of arid and semiarid regions. The aim of this ‎work was to investigate individual and combined effects of salinity and Cu on growth, leaf ‎relative water content (LRWC), cell membrane permeability, lipid peroxidation, and total ‎phenolic content (TPC) of rosemary (Rosmarinus officinalis L.) in a hydroponic ‎experiment. A factorial arranged experiment with three salinity levels (i.e., 0, 50, and 100 ‎mM NaCl), and three levels of copper (i.e., 0, 0.5, and 1.0 µM Cu2+, as CuSO4) was ‎performed. The salt stress led to a significant decrease in leaf relative water content ‎especially at 0 µM Cu2+. Salt treatments (50 and 100 mM) were found to increase ‎electrolyte leakage and malonyldialdehyde content of rosemary; however, this increase ‎was greater at 0 µM than 1.0 µM Cu2+. Regardless of Cu treatments, salinity (50 and 100 ‎mM) induced significant increases in TPC by 13 and 29%, respectively. The application of ‎‎1.0 M Cu at the 50 mM NaCl treatments increased total phenolic content by 19% ‎compared to 0M Cu. Copper nutrition resulted in greater accumulation of phenolic ‎compounds in plant roots and thereby decreasing lipid peroxidation under salt stress ‎conditions.‎