Evidence for a Flow of Water into Sieve Tubes Associated with Phloem Loading

Evidence that there is a lateral water flow associated withthe loading of sieve tubes is presented. The change in phloemtransport dynamics, measured using ¹¹C, induced by leaf anoxiais shown to be consistent with a reduction in lateral waterflow brought about by a decline in sucrose loading. The temporalprofiles of tracer activity are used to derive a simple holisticmodel of the phloem pathway which is able to account for theobserved dynamics.