Germination characteristics along altitudinal gradients in three intermountain Allium spp. (Amaryllidaceae)

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Seed Technology





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Understanding the relationship between life cycle events of native species and their prevailing environmental conditions provides a framework in which site-specific propagation strategies can be developed. We examined the ecophysiological aspects of seed germination in three Allium species native to the Intermountain West (A. acuminatum, A. brandegei, and A. passeyi) to evaluate ecotypic variation in relation to the altitude of the collection site. Three populations of each species were evaluated along an altitudinal gradient. The study consisted of two laboratory experiments: 1) germination trials assessing the effects of moist chilling temperatures on germination percentage in each species; and, 2) germination trials measuring the response within and among species from contrasting habitats to moist chilling duration. The data demonstrate a strong among-species pattern of increasing dormancy with increasing elevation. Although germination in all three species responded favorably to moist chilling at 3 °C, there was significant variation in the chill duration required to break dormancy. The presence of a non-dormant fraction only in the lowest A. acuminatum collection, and all three of the A. passeyi collections also indicates a higher level of selection pressure against this trait in sites with longer and more predictable winters. The observed patterns in seed germination are typical of survival strategies in other spring ephemerals. This current understanding of the influence of habitat on germination traits in these Intermountain Allium species will aid in the development of seed-source specific propagation protocol.