Moringa oleifera Lam. Seed Extract Enhances Tolerance to Drought Stress by Regulating Photosynthesis and Antioxidant Defense Mechanism in Lessertia frutescens L.

Drought is a predominant environmental stress that limits plant growth and yield. Biostimulants including moringa (Moringa oleifera Lam.) seed extract (MSE) can alleviate adverse plant responses triggered by drought stress. Nonetheless, there is limited information regarding the functions of MSE in promoting drought tolerance in plants. Consequently, the current study investigated the effect of MSE on the enhancement of drought tolerance in cancer bush (Lessertia frutescens L.) plants under drought stress. The 6% MSE foliar spray was applied to cancer bush plants subject to standard [80% of soil water-holding capacity (SWHC)] and drought stress (60% of SWHC) in a terracotta pot experiment that was conducted twice sequentially in a tunnel. Plants that were not treated with MSE were used as control. The application of MSE effectively alleviated the adverse effect of drought stress on cancer bush by improving plant growth and yield characteristics, photosynthesis attributes, soluble protein, and free proline contents. The MSE mitigated lipid oxidation (malondialdehyde) of drought affected plants and enhanced the antioxidant enzyme activities. These results demonstrated that MSE application effectively alleviated drought stress in cancer bush plants. Therefore, MSE is an economical and eco-friendly biostimulant for enhancing plant performances under drought stress.