Pollen Development and Cytochemistry in Some Australian Species of Acacia

Abstract

Development of the 16-grained polyads of Acacia conferta, A. iteaphylla and A. subulata has been followed by use of high resolution light microscopy and cytochemical methods to reveal pollen wall structure, with a view to determining the mechanism of grain cohesion into polyads. The 16 microspores within each loculus are held within the callose special wall at tetrad period, but the wall is perforated by cytoplasmic connections linking the inner faces of the microspore. These connections are c. 2 μm in diameter and are apparently cytoplasmic since they stain strongly with Coomassie blue and other protein stains, and may determine the sites of exine wall bridges found in mature polyads.

At maturity, polyads are held within a membranous sac lined with orbicules. Radial wall thickenings of the endothecium were positively stained by decolorized aniline blue. A. subulata had 13 bivalents at meiotic prophase, 2n = 26 as in some other Australian species of Acacia.