Scarification Technique Affects Germination of Stylisma pickeringii (Patterson bindweed), an Illinois Endangered Plant

The seed coat of Stylisma pickeringii (Torr.) Gray var. pattersoni (Patterson bindweed), an endangered species of Illinois sand prairies, inhibits water uptake and seed germination. The purpose of this research was to find an effective and efficient way to scarify seeds of S. pickeringii to aid reintroduction into its natural habitat. Seeds were collected from sandy areas close to the Illinois River near Snicarte (Mason Co.), Illinois during the summers of 1998 and 1999. Experiments were conducted to determine the best scarification techniques (basal cut, sandpaper shakes, sulfuric acid, sand shakes and sonication). Initially, each technique was evaluated by scarifying the seeds for different times (except for the basal cut). The optimal time for each scarification technique then was compared. Scarified seeds were germinated in petri dishes at 25 C, 16 h photoperiod, with a mean light intensity of 51 μ mol m−2s−1. The basal cut, 48 h sandpaper shake, 120 min acid soak and 72 h sand shake techniques did not differ significantly in germination (96, 92, 84 and 84%, respectively). The sonicator technique and the unscarified control yielded only 4 and 0% germination, respectively. For scarification of S. pickeringii seeds the 48 h sandpaper shake and 120 min acid soak were very effective and efficient relative to other techniques. Of these two techniques, the sandpaper shake is safer than the acid soak, although when scarifying large numbers of seed, the sandpaper shake would require a large shaker. The techniques have potential applicability to other threatened and endangered species whose seed coat also inhibits germination.