The Effects of Silicon Supplementation on Cucumber Fruit: Changes in Surface Characteristics

Addition of silicate to hydroponic nutrient media has been shown to increase resistance of cucumber to powdery mildew. As a side effect of this treatment, the fruit surface developed an unusual dull appearance, or bloom. The effects of silicate supplementation on cucumber fruit were observed using scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and colourimetric assays. Changes in the fruit trichome morphology occurred: trichomes from + Si fruit had a coarse outer appearance compared to - Si fruit where the trichomes were smooth. X-ray mapping showed high Si content in trichomes but not in the surrounding epidermis or fleshy mesocarp and endocarp tissues. Sections through the epidermal layer reveal that the silica is restricted to the trichomes, primarily in the epicuticular wax.