Studies on the regulation of algal growth by gibberellin

Abstract

CCC and Amo.1618, at relatively high concentrations only, inhibited the growth of excised branch apices of the redalga Hypnea musciformis. Neither GA3 nor GA7 stimulated growth of the alga in the presence or absence of these compounds, and gibberellin-like material extracted from H. musciformis also failed to stimulate growth. However, both gibberellins stimulated the growth of slow-growing, but not fast-growing, branch apices of the related red alga Gracilaria verucosa. It is concluded that endogenous gibberellins may not regulate the growth of H. musciformis, but this is likely to be a peculiarityof this species and not a general phenomenon in red algae. CCC inhibited the growth of gametophytes of the brown alga Ecklonia radiata, and GA3 significantly overcame this inhibition in a manner compatible with the concept of CCC inhibiting gibberellin biosynthesis. The complement of acidic, ethylacetate-soluble gibberellins extracted from those regions of E. radiata sporophytes active in cell division was chromatographically similar, but differed from those extracted from a relatively quiescent region of the alga. These data support previous conclusions that endogenous gibberellins are involved in the growth regulation of E. radiata. © 1971 CSIRO.