STRUCTURE AND SECRETION OF THE EXTRAFLORAL NECTARIES OF AUSTRALIAN ACACIAS

Abstract

ABSTRACT The extrafloral nectaries of A. pycnantha and A. myrtifolia are quite different morphologically but very similar ultrastructurally. The porate nectary of A. pycnantha has a deep goblet-shaped depression in transverse section with the secretory region at the base of the depression. The non-porate nectary of A. myrtifolia is a flattened gland with the secretory region in the centre of the nectary disc. In both species there are three cell types between the network of vascular bundles at the base of the nectary and the surface. The flanking zone consisted of thin-walled cells which merge into the glandular zone of thick-walled secretory cells. Carbohydrate, protein and lipid secretion products are visible in the intercellular spaces between the glandular cells and those of the surface secretory zone, which are loosely arranged. These nectar components appear to be transported outside the cell by both eccrine and granulocrine processes. The cuticle, very thin in the secretory zone, is distended by th...