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

Most wild Lupinus spp. (Fabaceae) grow in pine and pine-oak forests with natural and induced fi res. Their seeds have physical dormancy, which can be broken in response to appropriate environmental signals, such as high temperatures, humidity, and fi re. We applied heat treatments to break seed dormancy of L. elegans and L. rotundifl orus from the State of Jalisco, Mexico, with different storage times (0, 1, and 2 yr for L. elegans and 0, 1, 2, 3, and 4 yr for L. rotundifl orus). One set of seeds were immersed in boiling water for 5, 10, and 15 s, another set were incubated in wet or 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 and 150 °C. For L. rotundifl orus, germination was higher for seeds incubated in wet sand for 60 min than for those incubated for 90 min. Fresh seeds of L. rotundifl orus showed higher germination than stored seeds across treatments. After scarifi cation with boiling water, fresh seeds of L. elegans, germinated more than those stored for 1 and 2 year, whereas incubation in wet and dry sand resulted in higher germination for 1 and 2 year old seeds than for fresh seeds. Our results may be useful for further studies to understand and predict ecological plant responses in Mexican forests.

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