An electron probe X-ray microanalysis study during organogenesis from internode-derived nodules of Humulus lupulus var. Nugget

Abstract

Elemental changes during the induction of organogenesis from internode-derived nodules of Humulus lupulus var. Nugget were studied by electron probe X-ray microanalysis (EPMA) of specimens submitted to physical fixation procedures. X-ray spectra were collected from cambial and cortical cells. Four days after explants inoculation an increase of K and Ca was detected in cells of both regions. Four to twelve days after explants inoculation an increase of Cu, Zn, Fe, S and Mn was therein detected. Values of Cu, Zn, Fe, K and S were lower in control explants than in induced explants 12 days after induction. Although S presented fluctuations it increased throughout the induction period. X-ray spectra collected from organogenic nodules revealed higher levels of Ca, K, Fe, P and S on peripheral regions where regeneration was occurring. Ca was mobilized in several directions, from inner regions of nodules towards their periphery at the onset of plantlet regeneration. Levels of Mg and Na were low or absent. Control explants neither formed nodules nor regenerated plantlets. The results suggest that EPMA can be used to study relative elemental changes during plant morphogenesis induction and enables the early establishment of organogenic regions in nodules.