Sugarbeet Vasculature. II. Translocation of Assimilates in the Supernumerary Phloem

Sugarbeet plants and single leaves of different ages were exposed to 14CO2, and their assimilate translocation system was studied by autoradiography. The leaf traces nourish the entire secondary supernumerary phloem system across the beet. A single leaf nourishes a sector composed of primary and secondary vascular systems. This sector is wide in the outermost rings and narrow in the periphery of the pith. Accumulation of radioactive assimilates occurred throughout the entire cross section but remained in a relatively narrow band of each ring even 1 wk after labeling.