Role of the lens in physical dormancy in seeds of Sophora alopecuroides L. (Fabaceae) from north-west China

Although many studies have been done on seeds with physical dormancy, i.e. water-impermeable seed or fruit coat, the primary site of water entry into seeds after dormancy-breaking treatments is still controversial. In this work, the role of the lens in physical dormancy breaking was examined. The present study investigated the primary site of water entry and changes in seed-surface features for seeds of Sophora alopecuroides L. following various periods of scarification with sulfuric acid, hot-water treatments, and exposure to field conditions. Most seed coats first cracked in the hilum when pre-treated with sulfuric acid and after field exposure, but they cracked in both the hilum and extrahilar regions when treated with hot water. After pre-treatment, seeds first became slowly permeable in the hilum or extrahilar region and not in the lens. Acid scarification for 35 or 50 min caused the lens to crack, thus causing seeds to enter a fast imbibition stage. Seeds exposed to field conditions had further damage to the hilum, causing them to enter a fast imbibition stage. Imbibition time is a key point that determines the primary site of water entry into seed, and at least in part explains various results and interpretations about the role of the lens in physical dormancy in previous research.