Electron-probe Microanalysis Studies of Silica Distribution in Barley (Hordeum sativum L.)

Silicon occurence has been investigated by means of epidermal peels, cryostat, and ultrathin sections of the internode, nodes, leaves, inflorescence bracts, and caryopsis of Hordeum sativum L. (cultivar Deba Abed) using the electron probe microanalyser. Analyses were made on growth stages during ear emergence and at maturity. The results indicate that silicon is present in the internode with the highest concentration associated with the opaline deposits. Detectable quantities are also found in the outer tangential walls of the long cells, in the walls of stomata, the sclerenchyma, and all vascular bundle regions. In mature upper internodes, silicifiation is confined to the upper third region, but this limit extends closer to the basal meristem with increasing age of internode. The nodes have a greater concentration in the radial than in outer tangential walls. Heavy deposits are found in the leaves but with considerable variation between blade and sheath, abaxial and adaxial surfaces, and the leaf position. The flag leaf contained the highest accumulations. In the inflorescence bracts (lemma and palea), silicon is detectable only in the abaxial epidermis and hypodermis. Awns are also heavily silicified with the highest concentrations in the sclerenchyma and trichomes.