Influence of Various Environmental Factors on Seed Germination and Seedling Emergence of a Noxious Environmental Weed: Green Galenia (Galenia pubescens)

Abstract

Green galenia is a South African woody prostrate perennial that was first recorded in Australia in the early 1900s and has since become a serious threat to indigenous temperate grasslands and surrounding agricultural areas. Laboratory and field based experiments were conducted to examine the effect of environmental factors on the germination and viability of green galenia seed. It was shown that green galenia was able to germinate over a broad range of temperatures, but short bursts (5 min) of high temperatures (80 C to 120 C replicating possible exposures to a fire) reduced seed germination. Seed germination was positively favored by light, declined rapidly in darkness, and decreased by > 80% at a depth of only 0.5 cm in soil. Water stress greatly reduced seed germination (45% germination at osmotic potentials below −0.2 MPa). Germination was completely inhibited at water potentials of −0.4 to −1.0 MPa. This species is moderately tolerant to salinity, with over 50% of seeds germinating at low levels of salinity (60 mM NaCl), and moderate germination (49%) occurring at 120 mM NaCl, it can germinate well in both alkaline (pH 10–83%) and acidic (pH 4–80%) conditions. The results of this study have contributed to our understanding of the germination and emergence of green galenia, and this will assist in developing tools and strategies for the long term management of this noxious weed in Victoria and other parts of Australia.