Control of Growth in Callitriche Shoots by Growth Retardants and Gibberellic Acid

Abstract

Shoots of the aquatic, Callitriche, form floating rosettes of leaves, the internodes of which elongate if the shoot is submerged, or treated at the water surface with gibberellic acid (McComb 1965; Wong and McComb 1967). It may therefore be tentatively proposed that submerged shoots synthesize more gibberellin than do floating shoots. To obtain further information concerning this hypothesis, investiga-tions have been carried out with the growth retardants Amo1618 and CCC, com-pounds which characteristically bring about dwarfing in higher plants, an effect reversed by gibberellin (e.g. McComb and McComb 1970), and which have been shown to inhibit gibberellin biosynthesis in certain systems (e.g. Baldev, Lang, and Agatep 1965; Dennis, Upper, and West 1965; Zeevaart 1966).