Movement of14C- and11C-labelled Assimilate in Wheat Leaves: the Effect of IAA

The rate of translocation of naturally-loaded, radiolabelled assimilate has been studied in leaves of wheat treated with IAA. The velocity was measured directly by following the movement of 11C-labelled material along the leaf. The kinetics of translocation were also estimated by using a two-compartment model to calculate the rate constant of disappearance of 14C from the fed area. IAA was applied at three different sites on the leaf and at various times up to 24 h before 14CO2 feeding. No effects of IAA were observed on: (1) direction and velocity of transport; (2) loading of assimilate into the phloem; or (3) the site and kinetics of unloading. These results are discussed with reference to the movement of IAA along the transport path and the use of different tissues as experimental systems.