Opaline Silica Deposition in Rye (Secale cereale L.)

Abstract

The types of opaline silica-bodies (opal phytoliths) which occur in the mature prophylls, radical and culm leaves, culms, and inflorescence bracts of rye ( Secale cereale L.) are described and figured. Silica-bodies are absent from the coleoptile, and the adaxial epidermis of the prophylls, leaf sheaths, and inflorescence bracts. The stages of silica-body formation in young radical leaf sheaths are also de- scribed. Alternative hypotheses for the origin of silica-bodies are discussed. epidermis have already been the subject of a number of investigations. Prat's systematic study (1932) of the elements of the grass epidermis included a description and classification of the cell types and their development, together with a brief survey of the characteristic epidermal features of a large number of species. Although Metcalfe (i960) included the silica-bodies of grasses as useful taxonomie characters, his direct observations were limited to the culm leaf blade. Parry and Smithson (1964, 1966) have studied the silica- bodies occurring in leaves and inflorescence bracts of a number of British grass species. In particular, they have studied the three-dimensional shape of silica-bodies and the way in which they are arranged in the epidermis. These workers examined isolated phytoliths obtained from acid-macerated prepara- tions as well as the more conventional surface preparations and sections. The description of silica-bodies occurring in rye ( Secale cereale L.) presented here is an attempt to make a more complete survey of silica-body types in a single species. The work formed part of an investigation into silica deposi- tion in rye. Further results from the investigation, including the pattern of silica deposition in the leaves and internodes and the time sequence of depo- sition, will be published separately.