Abstract.
Seed germination of Nicotiana tabacum L. cv. Havana 425 is determined by the balance of forces between the growth potential of the embryo and the mechanical restraint of the micropylar endosperm. In contrast to the gibberellin GA4, the brassinosteroid (BR) brassinolide (BL) did not release photodormancy of dark-imbibed photodormant seeds. Brassinolide promoted seedling elongation and germination of non-photodormant seeds, but did not appreciably affect the induction of class I β-1,3-glucanase (βGLU I) in the micropylar endosperm. Brassinolide, but not GA4, accelerated endosperm rupture of tobacco seeds imbibed in the light. Brassinolide and GA4 promoted endosperm rupture of dark-imbibed non-photodormant seeds, but only GA4 enhanced βGLU I induction. Promotion of endosperm rupture by BL was dose-dependent and 0.01 µM BL was most effective. Brassinolide and GA4 promoted abscisic acid (ABA)-inhibited dark-germination of non-photodormant seeds, but only GA4 replaced light in inducing βGLU I. These results indicate that BRs and GAs promote tobacco seed germination by distinct signal transduction pathways and distinct mechanisms. Gibberellins and light seem to act in a common pathway to release photodormancy, whereas BRs do not release photodormancy. Induction of βGLU I in the micropylar endosperm and promotion of release of 'coat-enhanced' dormancy seem to be associated with the GA-dependent pathway, but not with BR signalling. It is proposed that BRs promote seed germination by directly enhancing the growth potential of the emerging embryo in a GA- and βGLU I-independent manner.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Electronic Publication
Rights and permissions
About this article
Cite this article
Leubner-Metzger, G. Brassinosteroids and gibberellins promote tobacco seed germination by distinct pathways. Planta 213, 758–763 (2001). https://doi.org/10.1007/s004250100542
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s004250100542