Movement of [(14)C]sucrose along the stolon of Saxifraga sarmentosa.

The characteristics of (137)Cs transport along the stolon of Saxifraga previously reported have been confirmed for applied sucrose and natural assimilate. Long-distance transport is strictly unidirectional, with a symmetrical short-distance spread from the point of application. Only the latter takes place in a long piece of excised stolon. Transport is readily reversed when the parent plant is darkened and the daugther, plantlet allowed to photosynthesise. These findings strongly support a mass-flow mechanism for the stolon. They also confirm the value of (137)Cs as a tracer for assimilate movement, though in contrast to assimilate it suffers appreciable lateral leakage. Pulse labelling of the subtending leaf failed to produce a sharp peak of activity in the stolon. A flattening with time of the (14)C profile is considered to be due to differing linear velocities in parallel sieve tubes.