Auxin–cytokinin interaction in the inhibition, release, and morphology of gametophore buds of Plagiomnium cuspidatum from apical dominance

Abstract

Observations were made on the effects of indoleacetic acid (IAA), kinetin (K), benzyladenine (BA), and triiodobenzoic acid (TIBA) on the lateral buds of decapitated and intact gametophores of Plagiomnium cuspidatum (Hedw.) Kop. Gametophores were cultured in both solid and liquid Parker's nutrient medium and treated with hormones either in solution or in lanolin paste. Based on numbers of activated buds counted from day 16 to 24, it appeared that IAA, K, and BA, when supplied to the decapitated stump, can to varying degrees replace the inhibitory influence of the apical bud. Closer study, however, of activated and inhibited lateral buds suggests that only IAA in the presence of a cytokinin can maintain inhibition in a morphological and anatomical state which is similar to that of intact control plants. Treatment of intact gametophores with TIBA increased bud activation below the treatment ring. Based on bud morphology and anatomical observations in conjunction with records of bud activation response, endogenous auxins and cytokinins appear to be at suboptimal concentrations for growth at inhibited bud sites.