Independent translocation of 14C-labelled assimilates and of the floral stimulus in Lolium temulentum

Summary It is widely accepted that the floral stimulus produced in leaves is carried to the shoot apex passively in the phloem with the assimilate stream. Three kinds of evidence presented here suggest that the floral stimulus moves independently of the assimilates.Simultaneous determination of the velocities of translocation out of the seventh leaf blade, in comparable plants under the same conditions, yielded estimates of 1–2.4 cm/hr for the floral stimulus, and 77–105 cm/hr for ¹⁴C-labelled assimilates.The effect of the size of the seventh leaf on its ability to export assimilates or to initiate flowering was quite different. Leaves with only 14–26% of their final blade area emerged exported little assimilate, yet were highly active in inducing flowering.The effect of DCMU applications at a range of concentrations on the translocation of assimilates was quite different from their effect on the flowering response.