Seed Science Research 15: 281-307 (2005)
Plant hormone interactions during seed dormancy release and germination
Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, 302 Life Sciences Building, Baton Rouge, Louisiana 70803, U.S.A. (M.A.C.)
Received 27 May 2005; accepted after revision 27 August 2005
Figure 1. Hormonal interactions during tobacco seed dormancy release and germination and their effects on testa rupture and endosperm rupture. Dormancy release involves the light/gibberellin (GA) pathway and results in testa rupture. The light/GA pathway also promotes endosperm rupture. Class I ß-1,3-glucanase (ßGlu I) and other hydrolases are induced by the light/gibberellin (GA) pathway in the micropylar endosperm and facilitate endosperm rupture and radicle protrusion. Endosperm-specific ßGlu I expression and endosperm rupture are inhibited by abscisic acid (ABA). The light/GA pathway also counteracts ABA effects by promoting ABA degradation. Ethylene and brassinosteroids (BR) counteract ABA effects and promote endosperm rupture, but do not affect testa rupture. EREBPs (ethylene responsive element binding proteins) are transcription factors that mediate hormonal regulation of ßGlu I expression and endosperm rupture. BR and light/GA promote tobacco endosperm rupture by distinct signal transduction pathways. In addition, seed after-ripening is associated with decrease in ABA level and sensitivity and an increase in GA sensitivity or loss of GA requirement. A ‘plus’ sign means promotion and a ‘minus’ sign inhibition.
Please note that the figure above is a modified and colored version of Figure 1 of the review, also found on the "Seed hormones web page".
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