Transcellular Strands and Particle Movement in Mature Sieve Tubes

Abstract

I HAVE suggested elsewhere¹ that transcellular protoplasmic streaming is the major cause of translocation in vascular plants. The hypothesis depends on the existence of transcellular tubular strands which cross the sieve tube lumina and pass through sieve pores thus providing a structural basis for cytoplasmic communication throughout the vascular system. Within the tubular strands, microscopic structures, comparable with the thread-like constituents of hair cell cytoplasm¹ (and perhaps related to the endoplasmic reticulum seen in electron micrographs of plant cytoplasm^2,3) are thought to be continuous in the longitudinal direction and to be surrounded by a fluid matrix.