Allelopathic Effects of Water Extracts of Maize Leaf on Three Chinese Herbal Medicinal Plants

Plants generate various secondary metabolites named as allelochemicals that can be release into the environment and influence the growth and development of other plants or the same plant. The potential allelopathic effect of maize (Zea mays L.) on seed germination, seedling growth and physiology was investigated with three medicinal plants (Platycodon grandiflorum A. DC, Scutellaria baicalensis Georgi and Salvia miltiorrhiza Bge) with different concentrations (0, 0.5%, 1.0%, 2.5%, 5.0%, 10.0%). Low concentrations (0.5%, 1.0%) of maize leaf aqueous extract stimulated the germination and seedling growth (root length, shoot height, fresh weight) of all receptor plants significantly. With the concentration of the aqueous extract increased, the stimulating effects gradually decreased, and even changed into inhibited. The aqueous leachate of maize leaves exerted different allelopathic effects on physiology of different test medicinal plants. For Platycodon grandiflorum A. DC, there was no significant difference in photosynthesis rate at all the tested concentration compared with control. In Scutellaria baicalensis Georgi the lower concentration (0.5%, 1.0%, 2.5%) of leachates stimulated the net photosynthesis rate, yet the higher concentration (5.0%, 10.0%) decreased the net photosynthesis rate, and all the tested concentration have inhibited effects on Salvia miltiorrhiza Bge and decreased its net photosynthesis rate. However, the content of soluble sugar and soluble protein of all receptor plants were stimulated by low concentrations (0.5%, 1.0%, 2.5%) of maize leaf aqueous extract. Allelopathy can affect the seed germination, early seedling growth and physiology of three medicinal plants.