Sulfuric acid and hot water treatments enhance <i>ex vitro</i> and <i>in vitro</i> germination of <i>Hibiscus</i> seed

Abstract

Seeds of Hibiscus dasycalyx S. F. Blake and Shiller, a federally listed candidate endangered species and native to North America and two variants of Hibiscus acetosella Welw. ex. Hiern were scarified using sulfuric acid and hot water. The effects of the scarification methods on in vitro and ex vitro germination in both species were evaluated. Sulfuric acid scarification was very effective for in vitro and ex vitro germination of both forms of H. acetosella and H. dasycalyx seeds by dramatically
increasing germination rate and decreasing germination time. Acid scarification of H. acetosella seeds for 10, 15, or 20 min resulted in close to 90% germination within a week. Germination rates of about 70%
(ex vitro) and 80% (in vitro) were obtained in H. dasycalyx seeds treated with sulfuric acid. Germination rates of 54% (ex vitro) and 95% (in vitro) were achieved when H. dasycalyx seeds were treated with hot
water for 5 min, but exposing the seeds for 10, 15, or 20 min produced poor results in H. acetosella and H. dasycalyx as hot water scarification appeared to result in severe injury or death of the embryos. The
protocols described here constitute rapid, reliable and simple methods to germinate H. acetosella and H. dasycalyx seeds in vitro and ex vitro. These results can be valuable in commercial productions or research projects. In addition, the in vitro germination of H. dasycalyx can offer a valuable tool in conservation efforts for this threatened species.