Indirect Action of Benzyladenine and Other Chemicals on Flowering of Pharbitis nil Chois

Abstract

Benzyladenine (BA) brushed on the cotyledons of 4-day-old seedlings of Pharbitis nil Chois. markedly stimulates flowering. Greatest response is obtained for concentrations between 44 and 440 micromolar. The action of BA is on processes in the cotyledon as shown by the response to its site of application, to the dosage applied and to the requirement for its application prior to the dark period. There was little or no effect of BA Two other chemicals which were previously considered as specific inhibitors of processes of floral induction in the cotyledon jTris(2-diethylaminoethyl)phosphate trihydrochloride (SK&F 7997-A3) and cycloheximidel acted in the same manner as BA. Inhibitory effects of an illuminated cotyledon on flowering of Pharbitis were also shown to be mediated by interference of assimilate flow with transport of the stimulus for flowering.It has been established beyond doubt that the leaf is the photoresponsive organ in photoperiodic induction of flowering (5, 21). However, little progress has been made either in unraveling the metabolic processes of floral induction in the leaf, or in identifying the factor(s) subsequently transported to the shoot apex where flowering is evoked. The effect on flowering of applying various chemicals to the leafhas offered one, although indirect, probe for examining the metabolic events of induction. Specificity of action in the leaf has been argued on three grounds: (a) that the time of sensitivity to application of the compound is specific for the timing of induction in the leaf; (b) that the compound is ineffective or markedly less effective at the apex; and (c) that the compound is not transported to the apex. Only when these three criteria are met is it valuable to consider further implications of the action of a particular compound in leaf tissue.

Alterations in Source-Sink Patterns by Modifications of Source Strength

“…The vegetative sinks in the present experiments were young leaves approaching their peak strength (20). Similar compensatory changes in the export pattern from cotyledons of Pharbitis nil in response to differential treatment of the cotyledons have been shown recently by Ogawa and King (17).…”

[14C]‐Assimilate partitioning in photoperiodically induced seedlings of Pharbitis nil. The effect of benzyladenine

“…In Pharbitis nil, assimilate allocation to induced apices was studied with BA treatments (Ogawa and King 1979). BA was applied to indueed and non-induced cotyledons of Pharbitis nil, and the authors showed that BA promotion of flowering was due to the interference of BA with assimilate translocation from the cotyledons to the apices.…”

Inhibitory role of gibberellins in theobroxide-induced flowering of Pharbitis nil

“…Exposure of P. nil cotyledons to a dark period of 16 h results in flowering (Imamura, 1961). If one cotyledon is kept in continuous light (CL), however, the floral response to a single inductive dark period can be reduced (Imamura, 1961;Ogawa and King, 1979). Using apex cultures from P. nil as an assay system, the phloem exudates (PE) extracted from P. nil cotyledons grown under SD conditions gave flower-inducing activity (Ishioka et al, 1990(Ishioka et al, , 1991, whereas the exudates from cotyledons grown under CL conditions showed flower-inhibiting The photoperiodic conditions and treatments were described as in ''Materials and methods''.…”