AUTORADIOGRAPHIC STUDY OF THE PATHWAY OF TRANSLOCATION

Abstract

Autoradiography was used to determine the tissues and cells involved in the downward translocation of 14C and tritium labelled photosynthate. Improvements were made in existing autoradiographic techniques to minimize movement of water-soluble substances and to obtain high resolution. In the autoradiographs, patches of silver grains were located in the region of the phloem of stem and petiole veins. In squash, these patches were mainly confined to the area occupied by the sieve tube. It is concluded that longitudinal translocation occurs in sieve tubes rather than in other phloem cells.