[Dynamics of soil phenols in continuous cropping solar greenhouse and their effects on disease resistance-related enzyme activities in cucumber root].

The study showed that under solar greenhouse condition, the contents of soil p-hydroxybenzoic acid, ferulic acid and benzoic acid and their total amounts increased with increasing continuous cropping years, and were obviously higher after continuously cropped for 5, 7 and 9 years than for 1 and 3 years. Different concentration of soil phenols resulted in completely different effects on disease resistance-related enzyme activities in cucumber root, e. g., under lower concentrations (40 and 80 microg x g(-1)), the activities of phenylalanine (PAL), ployphenol oxidase (PPO) and peroxidase (POD) were increased, while under higher levels (120 and 160 microg x g(-1)), they were restrained. Therefore, the changes of soil phenol contents in continuous cropping solar greenhouse could be one of the essential factors affecting the disease-resistance of cucumber.