Distribution of silicon in cucumber leaves during infection by powdery mildew fungus (Sphaerotheca fuliginea)

Abstract

The distribution of silicon in the leaf epidermis of cucumber (Cucumis sativus L.) grown in hydroponic nutrient solutions supplemented with soluble silicates was examined using scanning electron microscopy and energy dispersive x-ray analysis. Silicon was found primarily in cells surrounding the bases of the trichome hairs. During infection by Sphaerotheca fuliginea (Schlecht.:Fr.) Poll., areas of host cell wall adjacent to the germinating hyphae showed altered surface morphology and high concentrations of silicon. Measurements of total hyphal length per colony showed the fungal colonies grown on silicate-treated plants were significantly smaller than fungal colonies grown on control plants. In the early stages of infection, the presence of high silicon surrounding colonies was correlated with lower fungal growth. Key words: silicon, x-ray analysis, hydroponics, Cucumis sativus, Sphaerotheca fuliginea.