Dormancy breaking and germination of Adenocarpus desertorum, Astragalus gines-lopezii and Hippocrepis grosii (Fabaceae) seeds, three threatened endemic Spanish species

Abstract

The effectiveness of different presowing treatments for removing hardseededness in Adenocarpus desertorum, Astragalus gines-lopezii and Hippocrepis grossi, three endemic and threatened perennial leguminous species of Spain, was evaluated. Untreated seeds of all three species were germinated over a range of constant (15, 20 and 25°C) and alternating temperatures (15/25 and 20/30°C) under a 16-hour light photoperiod. A considerable fraction of these seeds had physical dormancy caused by a water-impermeable seed coat. Germination was studied for seeds subjected to different presowing treatments: dry heat, hot water, ultra-low freezing, liquid nitrogen, freeze-thaw and mechanical scarification. The most effective method for promoting germination of Adenocarpus desertorum (two populations) and Astragalus gines-lopezii (two populations) was mechanical scarification with pliers. The highest germination percentages of H. grosii were reached by seeds mechanically scarified and also by seeds stored in an ultra-low freezer for 24 hours. Our data provided useful information in germination protocols for ex situ propagation of these three endemic and threatened species, being the first report on seed germination behaviour of Adenocarpus desertorum and Hippocrepis grosii.