Impact of Soil Drench and Foliar Spray of 24-Epibrassinolide on the Growth, Yield, and Quality of Field-Grown Moringa oleifera in Southwest China

Abstract

The effects of soil drench (SD) (0.4 and 0.8 mg plant−1) and foliar spray (FS) (0.02, 0.04, and 0.08 ppm) of 24-epibrassinolide on the growth, yield, and quality of field-grown Moringa oleifera were evaluated. The results showed that all of the SD and FS treatments enhanced the net photosynthetic rate, stomatal conductance, transpiration rate, total chlorophyll content, and nitrate reductase activity in Moringa leaves. Both SD and FS promoted vegetative and reproductive growth of Moringa, but FS at an excessive concentration could suppress reproductive growth. Within a certain concentration range, the effect of FS on the reproductive growth was superior to that of SD, whereas the effect of SD on vegetative growth was better than that of FS. All of the 24-epibrassinolide treatments except for FS 0.08 ppm increased the number of seeds per fruit pod, the yield of fruit pods per tree, and the yield of seeds per tree, but the yield of the plants treated with SD was lower compared with FS. The FS 0.04 ppm treatment significantly increased the contents of oleic acid and eicosenoic acid and reduced the content of stearic acid in the seeds. All of the SD and FS treatments increased crude protein content in the leaf powder and seeds of Moringa as well as vitamin C in the leaves. Our results showed that the optimal concentration of 24-epibrassinolide for FS was 0.04 ppm, and the optimal concentration for SD was inferred to be higher than 0.8 mg plant−1.