Provenance modulates sensitivity of stored seeds of the Australian native grass Neurachne alopecuroidea to temperature and moisture availability

Abstract

In the present study we assessed the sensitivity of stored seeds of the common grass Neurachne alopecuroidea R.Br. from south-western Australian sources to varying temperature and moisture conditions as a tool to anticipate potential adaptability of seeds to climate change. We examined among-population germination responses, focusing on germination of excised seeds to overcome possible dormancy imparted by the lemma and palea. We hypothesised that temperature above and below the optimum and low moisture potentials would adversely affect germination, and that conditions for successful germination would be associated with the local climate at each seed source site. Experiment 1 used a bi-directional temperature gradient plate to measure responses to constant and alternating temperatures (5–40°C). Experiment 2 examined responses to moisture availability using polyethylene glycol (PEG 8000) solutions at different temperatures. Temperature optima varied among populations with significant reductions in germination occurring only below 15°C. Germination speed and success declined with decreasing moisture availability, with greater impact at higher temperatures. Significant population variation was observed. Tolerance to temperature and moisture availability was higher than expected and some of this variation suggests adaptation to local climates across the species Western Australian distribution. We discuss these results in the context of seed use in restoration and global warming.