The Active Compound in Rheum Officinale Baill, Aloe-Emodin Promotes Tomato Seedling Growth

Long-term excessive use of chemical fertilizers led to serious environmental pollution and food safety problems. Natural biostimulants are complimentary to pesticides and fertilizers, which can regulate plant growth and metabolism via promoting nutrient absorption and improving the ability to resist abiotic stresses. Vegetal extract, rich in bioactive substances, is one type of biostimulants. We determined the concentration of predominant active compound aloe-emodin in Rheum officinale Baill (R. officinale) extracts using LC-MS/MS. We applied either R. officinale extracts or aloe-emodin to tomato seedlings at the vegetative stage via different ways including spraying foliar (S), root irrigation (R) or spraying foliar and root irrigation (SR). Both R. officinale crude extracts and aloe-emodin could promote the growth of tomato stem and root, improve the photosynthetic capacity of leaves, improve the biomass of tomato, and ultimately lead to the vigorous growth of tomato plants. Clustering analysis and correlation analysis further confirmed that the effect was best in R application mode. Extracts of R. officinale and its active component aloe-emodin have been shown to increase the growth of tomato seedlings, implying that R. officinale could be a source of biostimulants.