Some recent advances in studies of silicon in higher plants

Abstract

In comparison with elements commonly associated with the nutrition of higher plants, silicon has received relatively little attention. Recently developed techniques have, however, demonstrated its occurrence in a wide range of tissues and species. Grasses are heavy accumulators, but considerable variation occurs between and within species. The factors involved in uptake, translocation and deposition in different species are not fully understood. Deposition has been investigated in the roots of a number of species. Active or passive uptake or almost complete exclusion has been observed. While deposits most frequently occur in cell wall layers or in cell lumina of the root endodermis, the major influx remains in a soluble form and is translocated to the shoot. Deposition is heavy in grass and cereal inflorescence bracts. Silica has also been detected in the epicarp hairs of cereal grains, and evidence is presented regarding the time course of its accumulation in these hairs. It is suggested that such deposition cannot be entirely attributed to a passive transpiration mediated mechanism. The significance of these deposits is discussed in relation to plant growth and development, and to wider aspects associated with human health.