Some effects of IAA and kinetin upon the movement of sugars in the phloem of willow

Abstract

Isolated bark strips of willow were sealed on to polythene tubes having three compartments. Colonies of the aphid Tuberolachnus salignus Gmelin were established on the bark at each end of the strip. IAA or kinetin at a concentration of 10^-5M was applied to the cambial surface of the strip in one of the end compartments, whilst either ¹⁴C-labeled sucrose or ⁸⁶RbCl was applied in the centre compartment. Both IAA and kinetin caused the activity from the ¹⁴C-Sucrose to move away from the area of their application, as measured by the specific activity of the honeydew collected from the aphid colonies. No effect of these hormones was demonstrated on the movement of ⁸⁶Rb. The results from further experiments in which sieve element exudate was collected via the severed stylets of the aphid, indicate that IAA and kinetin increase the rate of loading of sugars into sieve elements, i.e. the source capacity of the bark to which they are applied.