PHOTOCONTROL OF DEVELOPMENT OF EXCISED ERAGROSTIS EMBRYOS

• 1 Both the germination of intact seeds and the development of excised embryos depend on their after-ripening. Shortly after the harvest, the intact seeds of Eragrostis ferruginea are in dormancy and germinate neither in the light nor in the dark. The ability of seeds to germinate under both conditions, however, gradually increases with the progress of after-ripening. The development of excised embryos, on the other hand, is readily induced in the light and dark even shortly after the harvest. As the after-ripening proceeds, however, the ability of excised embryos to develop gradually decreases and is finally lost 18 months after the harvest. The after-ripened embryos whose ability to develop is completely reduced become light sensitive again when they are supplied with the yeast extract of a low concentration, and develop readily even in darkness at a high concentration of the extract.
• 2 The photorequirement for development of excised embryos is scarcely affected by oxygen concentrations, and the embryo growth can take place equally in both light and darkness in the atmosphere containing 100 to 10 percent of air, while it can not be induced in pure nitrogen.
• 3 The promotion of embryo development by light is observed at the time when the ability of embryos to develop declines. The effectiveness of the irradiation is very similar to that in intact seed germination.