Germination and dormancy release of seeds of Australian native understoreyspecies used for minesite rehabilitation

Temperature and pre-treatment effects on the germination of seven Australia n native understorey species were studied to determine environmental condit ions to maximise germination when broadcast to revegetate mined land. Germi nation responses to temperatures ranging from 5 to 40 degrees C; transfer f rom the temperature extremes to 22 degrees C; mechanical. acid and thermal (water at 80 degrees C or 100 degrees C) scarification; and the effect of l ight or dark were investigated. Seeds of Calytrix tetragona and Bursaria sp inosa germinated only when placed at 15 or 22 degrees C. In contrast, speci es of the Fabaceae family, Hardenbergia violacea, Kennedia rubicunda, Kenne dia prostrata, Indigoferra australis and Gompholobium latifolium germinated over a wider temperature range, 10 to 32 degrees C. There was no germinati on of seeds of any of the seven species at 5 degrees C. Moist incubation at 5 degrees C for 14 days prior to seed transfer to 22 degrees C increased t he subsequent rate of seed germination at 22 degrees C. Compared to the res ponse of seeds kept continuously at 22 degrees C, exposure to 5 degrees C f or 14 days prior to transfer to 22 degrees C considerably reduced germinati on of K. prostrata and slightly reduced that of other species. Relatively f ew seeds germinated after they had been incubated at 40 OC even if the seed s were transfered to 22 degrees C after 14 days at 40 degrees C. Unlike the low temperature 5 degrees C treatment, exposure to 40 degrees C killed the seeds. Light generally did not affect germination with the exception of tw o species, G. latifolium and K. rubicunda, which showed an interaction with scarification. Scarification generally improved both percent and rate of s eed germination of most Fabaceae despite significant differences between th e type and duration of the scarification treatments. Maximum germination of the smaller-seeded species, G. latifolium and I. australis, was obtained f ollowing pre-treatment with acid or hot water at 80 degrees C. The larger s eeds of H. violacea required boiling or nicking for optimum germination. Th e temperature requirements of these seven species indicate they have the po tential to germinate on minesites in the Hunter Valley whenever moisture is available. Low temperatures will delay germination while conditions of hig h summer temperatures exceeding 40 degrees C and rainfall would cause seed mortality. Seed treatments are recommended for the Fabaceae and vary depend ing on the species.