Ultrastructure of actinorhizal root nodules of Chamaebatia foliolosa (Rosaceae)

Abstract

The structure of the root nodules of Chamaebatia foliolosa Benth. (Rosaceae) has been studied by optical and transmission electron microscopy. The prokaryotic endophyte exhibits two morphological forms: septate hyphae and nonseptate elliptically shaped endophytic vesicles. This microorganism resembles the actinomyceteous endophytes of other actinorhizal root nodules especially those present in Ceanothus, Dryas, and Purshia. The endophyte is always surrounded by a polysaccharide capsule and possesses glycogen granules, lipid droplets, and prominent nucleoids. The infected host cells contain prominent lobed nuclei, numerous small vacuoles, and many plastids which possess numerous granular inclusions and osmiophilic droplets. No endophytic sporangia were observed in these nodules.