seeds were germinated on a temperature-gradient bar lined with filter paper as described by Berti and Johnson (2008) for 9 d with nine thermal couple probes evenly spread along the bar inthe range of 1.1–39.0◦C. The thermocouples (copper-constantan)were attached flush to the aluminum bar with high temperature conductivity epoxy resin. The thermocouples were monitored witha CR-10X (Campbell Scientific, Logan, UT) data logger every 15 sand 1 h averages recorded. Seeds were placed in 3 rows of 10 at each thermal couple, each row served as an experimental replicate.Seeds were checked daily for germination and filter paper was remoistened as needed. Radical emergence of greater than 0.5 cm was considered germination, and the germinated seed was removed from the gradient bar. The entire experiment was performed three times.