Effect of some growth substances and antimetabolites on elongation of the first internode in epiphyllous buds of Bryophyllum tubiflorum Harv.

Abstract

The growth response of the first internode in epiphyllous buds of Bryophyllum tubiflorum to auxin (IAA), gibberellic acid (GA₃), kinetin and four antimetabolites, namely, 5-fluorodeoxyuridine (5-FDU), 5-fluorouracil (5-FU), actinomycin D and chloramphenicol under different light conditions has been investigated. It was observed that continuous white light and red light inhibited internodal elongation and that the light-induced inhibition could be reversed by exogenous GA₃. The IAA did not show any significant effect when used alone or in combination with GA₃ or kinetin. Kinetin inhibited internodal elongation under all light conditions. The 5-FDU and actinomycin D strongly inhibited the elongation, but 5-FU and chloramphenicol did not affect it significantly. The inhibition caused by 5-FDU and actinomycin D could not be eliminated by GA₃. It is concluded that the internodal elongation in these buds is under the control of an endogenous gibberellinlike substance(s), and exogenous IAA fails to produce any synergistic or additive effect with GA₃. A continuous DNA or DNA-dependent RNA synthesis is necessary for the effectiveness of GA₃.