The Influence of Low Temperature on the Rate of Translocation in the Phloem of Salix viminalis L.

The rate of phloem translocation in willow stems was found tobe little reduced on cooling considerable lengths of the transportpathway. Even when 65 cm lengths of stem were cooled from about23 to 0 ?C the reduction in rate was judged to be less than20 per cent. It is argued that the velocity of translocationis well maintained in cooled stems and that there is no goodcase for supposing that the concentration of the translocatehad altered. The rate of radial transfer of materials from thephloem to the xylem did show a decrease in cooled zones. Theimplications of the results on current theories of phloem transportare discussed.