Distribution of zinc in subterranean clover (Trifolium subterraneum L.) grown to maturity in a culture solution containing zinc labelled with the radioactive isotope ⁶⁵Zn

Abstract

Subterranean clover (T. subterraneum L. var. Bacchus Marsh) was grown to maturity in a culture solution containing zinc labelled with the radioactive isotope ⁶⁵Zn. The distribution of zinc in the plants at different stages of growth was determined by means of radioautographs. These show that zinc is always present in very high concentration in the terminal portions of the main axis, runners, and laterals, in young, expanding leaves and petioles, in root tips and at points along the roots, in parts of the inflorescences, and in developing and mature seeds. The concentrations decrease in the vegetative organs as they expand and mature. In mature vegetative organs there is usually a higher concentration of zinc in the vascular tissue than in the tissue surrounding it. A higher concentration of zinc is found in the nodes of the runners and laterals than in the internodes. In the nodes themselves the concentration is highest where the amount of vascular tissue is increased by the presence of the vascular traces of petioles and of runners, laterals, or branches.