Laboratory Growth Studies on Sargassum muticum (Yendo) Fensholt. II. Apical Dominance

Abstract

In S. muticum collected furing the late winter or early spring and grown in the laboratory, apical dominance was demonstrated at 2 levels. Primary apices inhibited the growth of secondary laterals and secondary apices controlled the development of tertiary laterals. In primary laterals the apical influence was only effective in the region near the apex and the strength of the effect decreased with increasing distance from the apex. Primary laterals did not interact, i.e., only lower order laterals were affected. When the apex was removed none of the lower order laterals became dominant over the others in the conditions described here, although this was observed in the field. Indol-3-ylacetic acid inhibited the expansion of apical segments of primary laterals at a concentration of 1 ppm.