Scanning Electron Microscopic Study on in Vitro Somatic Embryogenesis of Perennial Ryegrass and Tall Fescue

Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) are two major turfgrass species in the United States. Their improvement via biotechnology approaches depend on the tissue culture response, particularly in vitro plant regeneration. To understand more of the regeneration event, scanning electron microscopy was performed and somatic embryogenesis was revealed in both species. Somatic embryogenesis initiated from compact, granular sectors of a callus. Then the scutellum became obvious during the development, and the coleoptile formed later at the base of the scutellum. In perennial ryegrass, the coleoptiles sometimes split into two sectors that wrapped around each other, which was not observed in tall fescue. Moreover, root hairs were often observed on the somatic embryos of perennial ryegrass but rarely in tall fescue. The scutellum of somatic embryos of both species also exhibited a leafy nature as indicated by trichome formation on the surface of the tissue. The trichomes on the somatic embryos of perennial ryegrass were not as obvious nor as massive compared to tall fescue.