The effects of moisture stress on the germination of some Australian native grass seeds

Abstract

The effects of moisture stress on the germination of the native grasses Themeda australis, Bothriochloa macra, Danthonia spp. and Stipa bigeniculata and the introduced species Lolium perenne (ryegrass) were investigated under laboratory and glasshouse conditions. At osmotic potentials between -3 and -10 bars and soil water potentials between -4.5 and -10 bars, the level of germination of ryegrass was greater than that of the native grasses. Also, at any given soil water potential, the levels of germination of both ryegrass and the native grasses were greater in a clay soil than in a sandy one. When native grass seeds were sown on the surface of the soil in flats in a glasshouse there was no germination in the absence of added water, even though the initial soil moisture content was as high as 40 per cent in some cases and a straw mulch was applied. When flats were watered daily, Stipa had the highest percentage establishment and Themeda the least. Establishment of all species was reduced by a decline in soil moisture content.