Translocation of 11C from leaves of Helianthus: preliminary results

Abstract

11C fed to leaves as 11CO2 was used to study the dynamics of short-term translocation of photosynthate in Helianthus. As in 14C studies small amounts of tracer were often detected in the stem close to the fed leaf in the first 5 min, followed by a larger mass flow after 15 min. The speed of mass flow of tracer movement was calculated to be 60 to 400 cm ∙ h−1 depending on the method of calculation. There was no evidence in the premass flow for discrete spots along the stem or petiole where tracer accumulated. Neither was there firm evidence for pulses of tracer moving steadily forward, but there were point fluctuations of greater variability than would be expected by chance alone, which suggest the possibility of abberations of movement superimposed on the mass flow. Details of these abberations could not be assessed with certainty from these preliminary experiments owing to the rather low tracer activity.The translocation profiles were sensitive to the prior light conditioning of the plant and above all to chilling. In Helianthus the latter produced temporary restrictions in translocation which lasted for some 10–12 min.