Distribution of elements in the lily pollen tube tip, determined with the Oxford scanning proton microprobe

Abstract

Pollen tubes ofLilium longiflorum were fixed with glutaraldehyde and investigated unsectioned with the Oxford scanning proton microprobe (SPM). Two-dimensional maps which show the distribution and concentration of phosphorus, sulphur, chlorine, potassium, calcium, iron, copper, zinc and arsenic are presented. The maps show that, within the pollen tube tip region, calcium and zinc exhibit relatively steep longitudinal concentration gradients compared to the more flat distributions of phosphorus and sulphur. Chlorine, potassium, iron and copper appear equally distributed along the tube. All elements with the expception of arsenic show the highest concentration within the cell protoplasm and not in the cell wall. Additional signals of arsenic, chlorine and potassium originate from the remaining fixative dried around the tube, containing also the free ions of the cell. The arsenic signals originate exclusively from the buffer used during fixation. The different maps are compared and discussed in relation to their significance to the pollen tubes.