A method to label seeds and seedlings using gamma-emitting radionuclides

The A major obstacle limiting field studies in plant population biology is that there is no way of uniquely labeling or identifying the seeds produced by a mother plant so that her seedlings can be distinguished from the offspring of other conspecific plants. This article describes experiments undertaken to develop gamma—emitting radionuclide labels that are injected into a plant and are incorporated into the developing seeds and subsequent seedlings. The nuclides were used singly and in combination since each nuclide has unique spectral peaks that can be used to distinguish it from other nuclides. Five species were used: Phaseolus vulgaris, Polygonum pensylvanicum, Impatiens capensis, Bidens frondosa, and B. connata. Easily detectable levels of ⁵⁸cobalt, ⁶⁰cobalt, ¹³⁴cesium, ¹³⁷cesium, and ⁷⁵selenium were incorporated by seeds of the five species. The incorporation of ⁵⁴manganese and ⁶⁵zinc varied among the species. ⁸⁸Yttrium, ¹²⁵antimony, and ⁸⁵strontium were weak or not present as labels, depending on the species, while ¹¹⁰silver and ⁴⁶scandium were never found in the seeds. Bean seedlings showed readily detectable amounts of nuclide label, while the nuclides apparently leached out of the Impatiens seedlings. The quantities of nuclides used in these experiments were so low that there was no effect of radiation on plant performance. (author)