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.

Relationships between seed germination requirements and ecophysiological characteristics aid the recovery of threatened native plant species in Western Australia

“…This study also employed a number of these techniques to stimulate germination in threatened Western Australian taxa. Excision of seeds from the woody fruits of the Myoporaceae ( Myoporum and Eremophila ) as reported previously by Richmond & Ghisalberti (1994), and also for Hibbertia as reported by Schatral (1996) and Schatral et al (1997), produced high germination percentages in the study taxa. Fruit or seed coats may restrict oxygen and water exchange, and may create a physical barrier to radicle emergence (Beardsell et al 1993).…”

Germination of Lomandra sonderi (Dasypogonaceae) Promoted by Pericarp Removal and Chemical-Stimulation of the Embryo

“…Removal of the inner pericarp or leaching for 24 h promoted germination suggesting the presence of water soluble inhibitors in this tissue. Similar findings, in the form of a water soluble inhibitor, have been found in Eremophila fruit (Richmond and Ghisalberti 1994). However, applied extracts from inner pericarp tissue did not prevent embryo growth in L. sonderi.…”

“…Merrill & Perry, inhibitors in the fleshy pericarp reduce seed germination by one-third (Ashton and Frankenberg 1976), and fruit extracts completely inhibit germination in Eremophila R.Br. (Richmond and Ghisalberti 1994). Flesh removal occurs naturally through decay or consumption of fruit by animals.…”

Fruit processing, seed viability and dormancy mechanisms of Persoonia sericea A. Cunn. ex R. Br. and P. virgata R. Br. (Proteaceae)

“…However in this species chemical dormancy also played an important role; water-soluble germination inhibitors were found within the fruit wall (Richmond and Ghisalberti 1994). The 11 removal of the endocarp from P. virgata E+S by cracking with pliers was easier than cutting with a scalpel.…”