Determining the Effect of Physical Treatments on the Promotion of Seed Germination in Green and Giant Foxtails

The difficulty of breaking seed dormancy in Setaria (foxtail) species presents a problem in using them as model plants. In the present study, we observed the structure of the seed coat surface of two Setaria species, the green foxtail (Setaria viridis) and the giant foxtail (Setaria faberi), using an electron microscope in order to clarify the factors of difficulty in breaking seed dormancy. In addition, we tested the effects of physical treatment on Setaria seeds using four treatments: (1) Removing the outer seed coat, (2) Removing the outer seed coat+mechanical scarification of the inner seed coat (the seeds were scarified using sand-paper with grit 350–2000), (3) Removing the outer and inner seed coat, and (4) No treatment (control). During the observation using electron microscope, we found a structure that was supposed to repel water (which is called the ‘lotus effect’). We found that seed germination in Setaria species can be induced by removing the outer seed coat along with mechanical scarification of the inner seed coat (second treatment) as well as by removing the outer and inner seed coat (third treatment), whereas seed germination was not observed after removing only the outer seed coat and no treatment.