Germination of Hymenachne amplexicaulis and H. acutigluma under contrasting light, temperature and nitrate regimes

Shane D. CampbellA, Elizabeth A. CarterA,B and Melissa J. SetterC

A Tropical Weeds Research Centre, Biosecurity Queensland, Department of Primary Industries and Fisheries, Queensland 4820, Australia.

B University of Queensland Gatton College, Queensland 4343, Australia.

C Centre for Wet Tropics Agriculture, Biosecurity Queensland, Queensland Department of Primary Industries and Fisheries, PO Box 20, South Johnstone, Queensland 4859, Australia.


A laboratory experiment compared germination of the invasive exotic grass Hymenachne amplexicaulis (Rudge) Nees and the native H. acutigluma (Steud.) Gilliland. Seeds of both species were exposed to combinations of light (constant dark, alternating dark/light or constant light), temperature (constant or alternating) and nitrate regimes (with or without the addition of KNO3). Three seed lots of H. amplexicaulis (fresh, two and four months old) and one of H. acutigluma (fresh seed) were tested.

A significant temperature x light x nitrate x seed lot interaction occurred. At a constant temperature very few seeds of either H. amplexicaulis or H. acutigluma germinated, regardless of the light regime or addition of KNO3. Generally, maximum germination occurred under a combination of alternating temperature, the presence of light (either constant or alternating) and the addition of KNO3. The exception was four month stored H. amplexicaulis seed, which reached maximum germination without the need for KNO3. Fresh seeds of both H. amplexicaulis and H. acutigluma exhibited similar germination requirements.

These findings suggest that conditions that buffer seeds from light and/or temperature fluctuations could reduce germination and possibly extend the life of seed banks of both H. amplexicaulis and H. acutigluma. Conversely, for land managers trying to control the exotic H. amplexicaulis, activities that create more favourable conditions for germination may help deplete seed banks faster.


Plant Protection Quarterly (2009) 24 (1) 10-14.