Taxonomic Implications of Fracture Load and Deformation Histograms and the Effects of Treatments on the Impermeable Seed Coat of Acacia Species

Abstract

Preliminary compression studies of over 20 Acacia species indicated that each species had characteristic fracture load and deformation histograms. It seems feasible that with refinement the compression technique could be used for taxonomic differentiation of closely related species. Significant differences were revealed by the technique in fracture load and deformation behaviour, in maximum deformation energy and in the effects of dry and moist heat between A. longifolia and A. sophorae from different parts of Australia. Heat and microwave energy have a 'softening' effect on the seed coat in the physical sense but this was shown to be insufficient to make the coat as a whole permeable to water. More evidence is given to support the thin shell theory on the mode of fracture of an impermeable seed coat under microwave energy and heat treatment. The depth of relative impermeability was found to extend well below the light line and almost to the end of the macrosclereid cells.