Gibberellic-acid-promoted transport of assimilates in stems of Phaseolus vulgaris L. : Localized versus remote site(s) of action.

Gibberellic acid (GA3), applied as a dispersion in aqueous lanolin to the stumps of decapitated stems of P. vulgaris plants, was found to promote the transfer of (14)C-and (32)P-labelled assimilates to the site of hormone application. Measurements of the component transfer processes, operating between source and sink (site of hormone application), showed that GA3 was not acting to promote assimilate transfer by increasing the photosynthetic rate of, or the assimilate export rate from the source, nor by altering the mobilizing ability of the competing root sink. Here, it also was found that the time between GA3 application and detection of an enhanced transport flux was independent of the length of the transport pathway. Overall, the evidence obtained indicated that GA3 was not acting on any transfer process remote from its point of hormone application but was acting locally at this latter point.