Priming effects on seed germination of two perennial herb species in a disturbed lava field in central Mexico

Priming has proved to enhance seed germination, but most of the research dealing with this topic has been carried out with cultivated species. The potential applications that this process has on wild species, which can be useful for restoration, are usually overlooked. This study analyses the germination response after natural priming and hydropriming of Penstemon roseus and Castilleja tenuiflora, two perennial herbs growing in a protected area known as Parque Ecologico de la Ciudad de Mexico'. Photoblastism was evaluated for both species. Seeds were exposed to a hydration/dehydration cycle and then placed in germination chambers to determine responses to hydropriming. To identify the effects of natural priming, seeds were buried in natural conditions and then recovered every two months and placed in germination chambers. Germination percentages and rates were then quantified. Both species proved to have permeable seed coats. Penstemon roseus seeds are positive photoblastic whereas C. tenuiflora seeds are indifferent to light. Priming methods increased C. tenuiflora germination rates, but they did not affect germination capacity. For P. roseus, priming methods did not improve germination rates, and germination capacity of recovered seeds decreased after the rainy season, suggesting that P. roseus forms a short-term, transient, seed bank. The germination strategies of these two species allow them to occupy suitable microsites for germination and establishment. These responses can be helpful in developing restoration programmes based on the accelerated establishment of native and characteristic successional species.