Seed Dormancy and Germination Mechanisms in Eremophila (Myoporaceae)

Abstract

Eremophila R.Br. (Myoporaceae) species are hardy perennial shrubs and trees which are endemic to Australia. They offer potential in revegetation and horticultural programmes and are currently propagated from cuttings, since they have proven difficult to grow from fruits. Fruits of E. maculata (Ker Gawl.) F.Muell. contain multiple seeds, and potential seed viability decreases from 58-74% over the first 3 years to 8% after 10 years. Up to 98% germination is obtained with seeds of E. maculata excised from the fruit, compared to 28% germination from the fruit. Since older fruits, which are characterised by a weathered fruit apex, allow a greater number of seedlings to emerge during optimum conditions, Eremophila germination appears to be controlled primarily by physical dormancy due to the woody endocarp which surrounds the seeds. Chemical dormancy also plays an important role in the establishment of Eremophila, and germination inhibitors have been found within the fruit wall of E. maculata and E. racemosa (Endl.) F.Muell. The inhibitors from E. maculata appear to be water-soluble aromatic glycosides. It is suggested that germination in the field is triggered by leaching of these compounds from the fruit during intense precipitation.