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., ۰, ۵۰, and ۱۰۰ ‎mM NaCl), and three levels of copper (i.e., ۰, ۰.۵, and ۱.۰ µM Cu۲+, as CuSO۴) was ‎performed. The salt stress led to a significant decrease in leaf relative water content ‎especially at ۰ µM Cu۲+. Salt treatments (۵۰ and ۱۰۰ mM) were found to increase ‎electrolyte leakage and malonyldialdehyde content of rosemary; however, this increase ‎was greater at ۰ µM than ۱.۰ µM Cu۲+. Regardless of Cu treatments, salinity (۵۰ and ۱۰۰ ‎mM) induced significant increases in TPC by ۱۳ and ۲۹%, respectively. The application of ‎‎۱.۰ M Cu at the ۵۰ mM NaCl treatments increased total phenolic content by ۱۹% ‎compared to ۰M Cu. Copper nutrition resulted in greater accumulation of phenolic ‎compounds in plant roots and thereby decreasing lipid peroxidation under salt stress ‎conditions.‎