Effects of grafted eggplants on allelopathy of cinnamic acid and vanillin in root exudates

Abstract: Cinnamic acid and vanillin are the allelochemicals commonly exist in eggplant root exudates. With pot culture experiment, the effects of grafted eggplants on allelopathy of cinnamic acid and vanillin in eggplants root exudates were studied. The results showed that cinnamic acid and vanillin had allelopathic effects on eggplants, lower concentration of cinnamic acid and vanillin (0.1 mmol L^-1 or 0.5 mmol L^-1) could promote the growth and physiological metabolism of eggplants, while higher concentration (from 1 mmol L^-1 to 4 mmol L^-1) had slightly promotive or inhibitive effects on eggplants. Meanwhile, this study suggested grafting could relieve autotoxicity of cinnamic acid and vanillin, and significant difference in the regulation intensity for the autotoxicity was found between cinnamic acid and vanillin. Grafting decreased the amounts of cinnamic acid and vanillin, especially of vanillin. The maximum reduction amount of cinnamic acid reached 68.96%, and that of vanillin reached 100%. Under the stress of exotic cinnamic acid and vanillin, especially of exotic cinnamic acid, grafting relieved the autotoxicity of the two substances on eggplants. Compared with own-rooted eggplant, grafted eggplant had a higher plant height and a larger stem diameter, its leaf cholorophyll content increased by 5.26-13.12%, root electric conductivity and MDA content decreased, and root SOD activity enhanced. Grafting was found to be one of the most effective methods for relieving replanting problems caused by autotoxicity.