Abstract
Seed germination completes when radicle emergence occurs through the surrounding tissues (testa and endosperm). To do this, embryonic growth potential should overcome the mechanical resistance caused by testa and endosperm. Therefore, germination processes require the activation of embryonic growth potential and weakening of surrounding tissues after seed imbibition. Hydrolytic enzymes of cell wall components are activated to weaken endosperm after seed imbibition. Gibberellin (GA) and abscisic acid (ABA) regulate the activation of these enzymes antagonistically. On the other hand, embryonic growth potential is activated in part by enhancing protein synthesis after imbibition. It is predicted that the protein synthesis is regulated by GA and ABA thorough the AtTCP/site II motif transcription complex. In this article, we summarize the functions of embryo and endosperm in terms of hormone actions.
