THE RELATION OF RAY SPACING TO CAMBIAL GROWTH

Abstract

An experimental test was made of Bünning's (1965) hypothesis that the tangential spacing of the rays is determined by mutual inhibitory effects of the ray initials. Partial girdles of trunks of Ailanthus altissima were prepared in such a way that regions of the cambium were obtained in which cell division and differentiation occurred rapidly in the radial direction but not along the circumference of the trunk. Though the spacing of the original rays was not changed by this restricted growth, it was found that the rays grew in volume and many new rays were initiated. This result suggests that the rays differentiate along channels of a stimulus moving between the phloem and the differentiating xylem and their spacing is controlled not in the cambium but in the differentiating vascular tissues. Copyright © 1972, Wiley Blackwell. All rights reserved