Quantifying the dormancy of Alopecurus myosuroides seeds produced by plants exposed to different soil moisture and temperature regimes

In pot studies, seeds of Alopecurus myosuroides were less dormant when produced under warm and dry, than under cool and wet conditions. The temperature to which plants were exposed had a greater effect on seed dormancy than soil moisture. The timing of temperature stress had a big impact on initial seed dormancy. The critical period was during seed maturation, irrespective of temperature conditions during the earlier phase of panicle emergence and anthesis. A much higher proportion (57-62%) of seeds collected from fields in 2001, 2003 and 2005 were non-dormant than in 2002 and 2004 (22-28%). Meteorological records showed that the mid-June to mid-July periods in England for 2001, 2003 and 2005 were warmer than average but in 2002 and 2004 were cooler than average. Consequently, results for samples collected from fields support those from experiments conducted under more controlled conditions. Studies in outdoor micro-plots showed that the differences in seed dormancy recorded with freshly produced seed did affect the rate of germination in the field, 2-3 months after shedding.