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Keywords:

  • Quantitative microanalysis;
  • wheat;
  • seed;
  • proton probe

Summary

A scanning proton microprobe has been used to determine quantitatively the distribution of Mn, Zn and other elements in the mature wheat seed (Triticum aestivum cv. Gamenya). Both X-ray and nuclear scattered proton data were collected during the irradiation of a 40 μm-thick longitudinal section, and these were used to calculate absolute elemental concentrations for the various features of interest in the embryo region. Elemental maps were collected for a number of transverse and longitudinal sections (obtained from several seeds), but comprehensive analytical information was collected from one typical longitudinal section only. In the embryo, the concentration (by dry weight) of Mn was highest in the radicle (1400 ± 200 μg g−1 error is 1 SD) and lowest in the coleorhiza (200 ± 30 μg g−1), whereas Zn was highest in the scutellum (600 ± 100 μg g−1 and lowest in the leaf primordium (410 ± 70μg g−1). Comparisons with direct bulk chemical analysis of excised embryos showed agreement. The possible biological significance of the distribution of elements is discussed. An extensive appendix allows botanists to properly assess the techniques used.