An Assessment of Moringa (Moringa oleifera L.) Seed Extract on Crop Water Productivity and Physico-Biochemical Properties of Cancer Bush (Sutherlandia frutescens L.) under Deficit Irrigation

Water deficit is a main abiotic stress limiting the cultivation of many plants including cancer bush (Sutherlandia frutescens L.), which is a traditional medicinal plant used to treat various diseases such as tuberculosis, cancer, diabetes and asthma. Natural plant growth hormones are a cost-effective and environmentally friendly alternative to synthetic growth regulators for plant production under favourable or adverse conditions. Thus, the current study investigated the biostimulant effect of moringa (Moringa oleifera L.) seed extract (MSE) on physiological and biochemical attributes, including crop water productivity (CWP) of cancer bush grown under deficit irrigation. The 2% MSE was foliar-sprayed to cancer bush plants subjected to full (100% of soil water holding capacity (SWHC)) and deficit irrigation (DI) (80, 60 and 40% of SWHC) in a pots experiment which was conducted and repeated twice consecutively in a tunnel. Plants that were not treated with MSE were considered as control. The results on water-deficit stress showed that the performance of cancer bush was significantly reduced in terms of growth and yield attributes, CWP, as well as physico-biochemical properties. Nevertheless, the foliar application of MSE on water-stressed plants effectively enhanced growth and yield characteristics, CWP, leaf photosynthetic pigments (chlorophyll "a", chlorophyll "b", total chlorophylls and total carotenoids), antioxidant activity (2 '-Diphenyl-1-picrylhydrazyl and 2,2 '-azinobis-3-ethylbenzothiazoline-6-sulfonic acid), relative water content (RWC) and membrane stability index (MSI) of cancer bush plants compared to respective controls. Therefore, the 2% MSE application was effective in mitigating negative impact of drought stress in cancer bush plants by maintaining higher RWC, MSI, CWP and biochemical attributes.