Dormancy and germination of Firmiana danxiaensis, an endangered tree endemic to South China

Abstract

Firmiana danxiaensis (Malvaceae) is a rare and endemic tree of South China. It has a very narrow distribution with only two extant populations in the wild. The aim of this study was to understand the nature of its seed dormancy, how to break the dormancy and the environmental requirements for the natural germination of its seeds. To identify whether seeds of F. danxiaensis are dormant, germination experiments with 12 treatments (three light levels × four temperatures) were conducted. To determine the optimal way to break dormancy, we conducted the dormancy-breaking experiment with five treatments, including physical and chemical methods. The results showed that the dormancy of F. danxiaensis seeds was associated with a water-impermeable seed coat, i.e., the seeds have physical dormancy. Soaking the seeds in 98% concentrated sulphuric acid for one hour overcame the physical dormancy and enabled imbibition followed by germination (up to 73%). Once dormancy was broken, F. danxiaensis seeds could germinate over a wide range of temperatures in both light and darkness. The results suggest that ex situ conservation and reintroduction of F. danxiaensis might be achieved by sowing acid-treated seeds at restoration sites at the appropriate time of year.