Seed Dormancy and Responses of Seeds to Phytohormones in Nicotiana plumbaginifolia

Abstract

We describe some characteristics of the dormancy in N. plumbaginifolia wild type seeds and ABA deficient I217 mutant seeds. The effects of the main phytohormones on germination were considered in relation to dormancy. It appeared that the depth of dormancy was correlated with variation in the sensitivity to every phytohormone, except ethylene. In particular, some cytokinins exerted a strong inhibitory effect on the germination of the slow germinating wild type dormant seeds which totally disappeared when seeds afterripened. Germination of the ABA deficient mutant was resistant to high levels of auxin and cytokinin but not ABA. Lastly, the very efficient effect on dormancy breaking of the ABA biosynthesis inhibitors norflurazon and fluridone implied an important role of ABA synthesis on the maintenance of dormancy in imbibed seeds.