Two-step model for tobacco seed germination

Figure 3.1: Working model for tobacco seed germination. Rupture of the testa and rupture of the endosperm are separate events in Nicotiana tabacum. Class I ß-1,3-glucanase (ßGLU I) accumulates just prior to endosperm rupture and is proposed to promote radicle protrusion by weakening of the endosperm. Plant hormones and environmental factors alter the germination process and in strict correlation with this either promote (+) or inhibit (-) ßGLU I induction. GA = gibberellin(s); ABA = abscisic acid; Pfr = Phytochrome. The model summarizes results from Leubner-Metzger et al. (1995, 1996, 1998).
© Review "Functions and Regulation of Plant ß-1,3-Glucanases (PR-2)" by Leubner-Metzger and Meins (1999)