Cell-Wall Structure in Apical Meristems

Abstract

Cytochemical and histochemical tests correlated with electron-microscope observations on fresh plant apical meristems (sectioned by the freezing-microtome method) reveal certain structural features of the differentiating cell wall, particularly with regard to orientation o? the cellulosic component. Newly initiated cell walls do not exhibit a uniformly thick sheet or plate of cellulose but show a pattern of transversely oriented cellulose-reacting strands with noncellulose-reacting areas occurring between these strands. As differentiation proceeds, an increase in the size and/or number of cellulose strands occurs, with an accompanying decrease in the size and number of noncellulosic areas. The formation of primary pit fields appears to result from this progressive differentiation. Plasmodesmata-like remains are seen within the primary pit field areas when viewed with the electron microscope.