Mechanism of Allelochemicals Inhibiting Continuous Cropping Cucumber Growth

Cinnamic acid and p-hydrobenzoic acid are main components of the allelochemicals in cucumber root exudates. Soil culture and water culture experiments carried through imitating the allelochemicals of the root exudates showed that cinnamic acid and p-hydroxybenzoic acid obviously inhibited continuous cropping cucumber growth. When the concentration of the allelochemicals was between 50 and 250μumol/L, the inhibition of cucumber roots from imbibing K+,NO3 and H2PO4 increased as the concentration increased, and so did the rate of nutrient leakage and the relative electric conductivity. Also cinnamic acid and p-hydroxybenzoic acid strongly inhibited the activities of root dehydrogenase, root-combined ATPase,NR and SOD. The higher the concentration,the stronger the inhibition. It was also found that cinnamic acid raised POD activity.