[Effects of silicon supply and Sphaerotheca fuliginea inoculation on resistance of cucumber seedlings against powdery mildew].

ABSTRACT

By the method of hydroponic culture, this paper studied the effects of soluble silicon (Si) supply and Sphaerotheca fuliginea inoculation on the active oxygen metabolism, SiO2 content and disease resistance of a susceptible cultivar. The results showed that the O2*- producing rate and H2O2 and MDA contents of cucumber leaf were increased by Sphaerotheca fuliginea inoculation, but reduced by the inoculation plus Si supply. The inoculation enhanced the catalase (CAT) and peroxidase (POD) activities in plant leaves but decreased their superoxide dismutase (SOD) activity, while inoculation plus Si supply increased the activities of these enzymes. Inoculation increased the scorbate (AsA) and glutathione (GSH) contents in plant leaves. The AsA content in Si-supplied plant leaves was lower than that of Si-deprived ones, whereas the GSH content was in reverse. Whether inoculated or not, the SiO2 content in Si-supplied plant leaves was significantly higher than that of Si-deprived ones. The disease index was significantly decreased by Si-supply.