The nature of surface growth in plant cells

Abstract

Autoradiographs have been prepared from parenchyma isolated from Avena coleoptile segments grown in a medium containing labelled glucose. The autoradiographs show that there is no concentration of radioactive material at the cell tips and labelled cellulose appears to be uniformly distributed in the cell wall. Electron micrographs of similar material show that the cellulose microfibrils are almost transversely oriented on the inner surface of the cell wall but are considerably dispersed from this direction on the outer surface. From this evidence it is concluded that growth in coleoptile parenchyma is not of the "bipolar" or "mosaic" types previously suggested, but corresponds to the "multi-net growth" of Roelofsen and Houwink. In addition a study has been made of the relation of microfibril orientation to cell form in parenchyma of onion root and in roots after treatment with colchicine, from which it is concluded that the final microfibril orientation on the outer wall surface is determined by the extent and polarity of its surface growth.