From Sand to Leaf
Silicon has for some time been recognized as a nutrient that is nonessential, yet imparts disease resistance in a number of plant families, such as the grasses and sedges. Historically, tissue levels of silicon have been used as the determinant of whether a plant is termed an “accumulator” or not. Accumulators have a silicon content of one-half to one percent, and a silicon:calcium ratio higher than one. However, it is known that some non-accumulators such as bean and aster take up significant amounts of silicon, which confers disease resistance. Unfortunately, this terminology may have limited the amount of research on species that are considered non- accumulators. Rather than having overall elevated silicon tissue concentrations, certain plants may channel silicon to specific locations. This occurrence was documented in impatiens (Balsaminaceae), and presented in the most recent Plant Health Progress.
USDA and University of Toledo researchers amended a soilless media containing peat and perlite (V:V) which contained impatiens cuttings with potassium silicate. The plants did not outwardly appear different from those plants that received only nutrient solution without silicon. However, the silicon-treated plants were stiffer to the touch, and the serrated edge on the leaf margin felt sharper than the control plants. When examined under a scanning electron microscope, it was found that silicon “scales” formed on the edges of the leaves. It was hypothesized that these structures may serve to deter pathogenesis in this popular foliage plant as well as others. (Plant Health Progress, 2/17/05).
