| Abstract: | Translocation studies were undertaken on a simplified singlesource leaf-single sink leaf sugar be system to test variouspredictions of the Ferrier and Christy (1975) mathematical recoverymodel translocation inhibited by cold. Experiments were performedby using a steady state MC-labellii system for the source leafand translocation into the sink leaf was monitored with a Geiger-Muellsystem. A specially designed Peltier apparatus enabled coolingof the source petiole to 1 ?C at vario positions on the petiole,as well as over different lengths. Results of experiments testingchanges in (1) cold block length, (2) cold block position, and(3) sink unloading rate, showed little difference in ti timecourse of recovery. These results are at variance with the predictionsof the mathematical recove model. Additional experiments wereperformed to assess the potential involvement of phloe anastomosesin the recovery response. Selective petiolar incision/excisionexperiments showed: (1) that the monitored sink obtained 14C-labelledmaterial via only a few of the vascular bundles within the sourcepetiole, and (2) that anastomoses were capable of re-establishingtranslocation. This information was used to develop a revisedmodel of translocation recovery following cold-induced inhibition,ai this model is based on the utilization of adjoining, interconnectedsieve-tubes which become integrat into the pathway that suppliesthis sink. Key words: Phloem, Translocation, Cooling, Anastomoses |
