[The autoradiographic identification of tritiated water-soluble material in the sieve tubes of Cucurbita and Cucumis].

When D-Glucose-6-T is applied to small areas of the leaf blade of Cucumis or Cucurbita, a translocation of labelled material within the veins and the petiole down to the internodes of the axis can be demonstrated by chemical methods and by histoautoradiography. The translocated material was identified by thin layer and paper chromatography as stachyose, raffinose, and sucrose. A dry mounting autoradiographic technique was elaborated which prevented any secondary diffusion of water soluble substances. In autoradiograms of longitudinal and cross sections of veins, petioles and internodes, tritium can be localized within single sieve tubes of exporting bundles. Usually the centre of activity corresponds to the cytoplasmic material or the slime-plugs and to the sieve plates. Since sucrose, stachyose and raffinose are the main labelled translocated substances in these experiments, there is little doubt that with certain precautions such autoradiograms may present a real picture of the long-distance translocation of assimilates.