Ultrastructure and function of the nectaries of New Zealand bracken (Pteridium esculentum (Forst. f.) Cockayne)

Abstract The ultrastructure of the nectaries and surrounding tissue of New Zealand bracken (Pteridium esculentum (Forst. f.) Cockayne) is described. There are no differences in the ultra-structure of bracken nectaries from New Zealand compared with material from Hawaii (Pteridium decompositum Gaud.) and California (Pteridium aquilinum (L.) Kuhn var. pubescens Underw.). The ultrastructure changes with the developmental state of these extrafloral nectaries. While the nectariferous tissue of young and actively secreting nectaries appears densely stained under the light microscope and has distinct ultrastructural features, the difference between the secretory tissue and the surrounding parenchyma becomes less obvious as the nectary ages and secretion ceases. A qualitative assay for sugar analysis demonstrated that New Zealand bracken nectaries actively secrete nectar.