Seed dormancy and the control of germination

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Abstract
Summary: Seed dormancy is an innate seed property that defines the environmental conditions in which the seed is able to germinate. It is determined by genetics with a substantial environmental influence which is mediated, at least in part, by the plant hormones abscisic acid and gibberellins. Not only is the dormancy status influenced by the seed maturation environment, it is also continuously changing with time following shedding in a manner determined by the ambient environment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth. In this review, we present an integrated view of the evolution, molecular genetics, physiology, biochemistry, ecology and modelling of seed dormancy mechanisms and their control of germination. We argue that adaptation has taken place on a theme rather than via fundamentally different paths and identify similarities underlying the extensive diversity in the dormancy response to the environment that controls germination. Contents Summary 501 I. Introduction 502 II. What is dormancy and how is it related to germination? 502 III. How is nondeep physiological dormancy regulated within the seed at the molecular level? 509 IV. How is nondeep physiological seed dormancy regulated by the environment? Ecophysiology and modelling 514 V. Conclusions and perspectives 518 Acknowledgements 519 References 519 Supplementary material 523