A new examination of anatomical structures characterizing the genus Gunnera

Abstract

We investigated selected species of the six subgenera of the genus Gunnera (Gunneraceae, Gunnerales, basal core eudicot) in order to confirm and to particularize for this taxon trait specifics on the occurrence of endodermis with Casparian bands in the organs of these representative species and to relate this endodermis to the structure of the vascular tissues. The general presence of endodermis with Casparian bands in stems and the vascular tissue arrangement varying from monostele to complex siphonostele is particularly specific for the genus. Petiolar endodermis was also characteristic and some species even had an endodermis surrounding veins in leaf lamina. Similarity of vascular tissue in stems and petioles in Gunnera species to seedless vascular plants is an interesting structural trait regarding phylogenic position of the genus. Only two species had simple, tetrarch to pentarch root vascular patterns common for eudicots, whereas all others were hexarch to multiple polyarch.