, a few infected cells in the fixation zone started to show the very early stage
of senescence (Fig. 8a). In contrast, the nZnO exposed-infected nodules
showed five distinct zones: a meristemzone, an invasion zone, an interzone,
a small nitrogen fixation zone, and a large senescence zone
(Fig. 8b). The delay in nodulation in the presence of nZnO was partially
recovered at 14 dpi, but senescence occurred much earlier than that of
controls.