Cell-Wall Formation in Root Hairs

Abstract

ELECTRON microscopic studies of the cell-wall organization in root hairs have shown that the microfibrils of the cellulose framework have a random orientation on the outer surface1,2 of the cell but on the inner surface they have an axial orientation2. This inner axially oriented layer was considered by Roelofsen2 to be secondary thickening. In view of the extensive evidence3,4 of the extremely localized tip growth of root hairs, the growth of these cells has been examined in recent work in this laboratory to assist in interpreting results relating to autoradiographic studies of growth of cells in which localized growth may take place. In the course of this work autoradiographs have been prepared of root hairs grown in solutions of glucose labelled with carbon-14 under varying conditions. Oat seeds were germinated on wet filter paper and then immersed in a solution containing 10 µc. of labelled glucose in 5 ml.; (the total glucose concentration being adjusted to 1 per cent with unlabelled glucose) under the following conditions : (a) Continuous immersion in the labelled glucose solution; (b) 16 hr. in labelled glucose and 36 hr. in unlabelled glucose (1 per cent); (c) 36 hr. in unlabelled glucose followed by 3½ hr. in labelled glucose.