Heat shock effect in breaking physical dormancy in seeds of lupinus elegans and L. Rotundiflorus from Jalisco, Mexico

Most Lupinus spp. (Fabaceae) grow in pine and pine-oak forests with natural and induced fires, and their seeds have physical dormancy, which could be broken in response to appropriate environmental signals, such as high temperatures, humidity and fire. We applied heat treatments to break seed dormancy of L. elegans and L. rotundiflorus from the State of Jalisco, México, with different storage times (0, 1 and 2 yr for L. elegans and 0, 1, 2, 3 and 4 yr for L. rotundiflorus ). Seeds were immersed in boiling water for 5, 10, and 15 s and incubated in wet and dry sand at 100 °C, 120 °C, and 150 °C during 60 min and 90 min. Germination trials were set at 25 °C with 12 h of irradiance per day. For both species, no germination resulted after incubation at 120 °C and 150 °C. For L. rontundiflorus , germination was higher for seeds incubated in wet sand for 60 m than for those incubated for 90 m. After scarification with boiling water, fresh seeds of L. elegans , germinated more than those stored for 1 and 2 yr, whereas incubation in wet and dry sand resulted in higher germination for 1 and 2 yr old seeds than for fresh seeds. Fresh seeds of L. rotundiflorus showed higher germination than stored seeds across treatments. Our results may be useful for further studies to understand and predict ecological plant responses in Mexican forests.