| Abstract: | Sieve-tube exudate was obtained as honeydew from colonies ofthe aphid, Tuberolachnus salignus (Gmelin), feeding on isolatedstem segments of willow. Potassium and sodium were shown tobe present in this honeydew. On perfusing the xylem with a solutionof potassium or sodium chloride, a considerable uptake of thecation took place. This uptake was followed, after a periodof several hours, by an increase in the concentration of theparticular cation in the honeydew. A relationship was shown to exist between the concentrationof these cations in a given segment and their concentrationin honeydew obtained from that segment. No such relationshipexisted, however, with different segments. These results arediscussed in relation to the factors which possibly controlthe movement of solutes into the sieve tube. |
