Improving Salt Tolerance of Helianthus annuus (L.) Plants by Moringa oleifera Leaf extract

TWo Field experiments were conducted to study the effect of seed soaking and/or foliar application with Moringa oleifera leaf extract (MLE; 1 extract paste: 30 tap water) on growth, physio-chemical attributes, anatomy and yield of sunflower (Helianthus annuus L.) plants grown on a sandy loam soil (EC = 6.42 – 6.48 dS m-1). The MLE application used as seed soaking or foliar spray significantly increased growth characteristics (i.e., shoot length, number and area of leaves per plant, and shoot dry weight), physio-chemical attributes (i.e., Relative water content (RWC%) and membrane stability index (MSI%), concentrations of total chlorophylls, total carotenoids, total soluble sugars, free proline and ascorbic acid, contents of N, P, K and Ca, and ratios of K/Na, Ca/Na and K+Ca/Na), antioxidant enzymes (superoxide dismutase, ascorbate peroxidase and glutathione reductase), seed yield, and seed oil and protein contents, when compared with the controls (seed soaking and foliar spray using tap water). Further, the MLE application used as seed soaking in combination with foliar spray significantly increased all aforementioned parameters and improved stem anatomy compared to the control and the single (seed soaking or foliar spray) treatments with MLE. In contrast, there were significant reductions in leaf electrolyte leakage (EL%), Na% and the enzyme catalase activity. The combined treatment of seed soaking and foliar spray with MLE was found to be highly effective in improving the growth and yield of sunflower plants by alleviating the inhibitory effects of soil salinity stress.