Allelopathic effects of cinnamic acid and vanillin on soil microbes, soil enzymes activities and growth of grafted eggplants

摘要

The contents of cinnamic acid and vanillin in eggplants root exudates and continuous cropping soil were determined by HPLC method. The results showed that the two allelochemicals excreted from the roots remained in soil and gradually accumulated in soil with the growth stage and continuously planting for many years. The allelopathy of cinnamic acid and vanillin on soil microbes, soil enzyme activities and growth of grafted eggplants was studied. Application of both allelochemicals (cinnamic acid, vanillin) changed the microbes population of grafted eggplants and increased the bacteria (1.80-9.00%), actinomycetes (0.89-17.19%), but, fungi was decreased (0.32-11.15%) over ungrafted eggplants. Compared with ungrafted eggplants, grafted eggplants had higher activities of soil enzymes (catalase, polyphenoloxidase, urease, protease and saccharase). After application of cinnamic acid and vanillin, the protease activity was enhanced markedly from 0.40 to 17.44%. The grafting affected the development of microbes and changed their relations between the bacteria, actinomycetes and fungi and made eggplants resistant to allelochemicals stress. The grafted eggplants grew taller, had larger stem diameter, increased the leaf chlorophyll content (3.90-16.0%), reduced the root relative conductivity and decreased the MDA content, while, the root SOD activity was enhanced over the ungrafted eggplants under cinnamic acid and vanillin stress. It may be possible that mechanism to resist allelochemicals stress in grafted eggplants improved the soil biological environment.