Emerging into the world: regulation and control of dormancy and sprouting in geophytes

Geophytic plants synchronize growth and quiescence with the external environment to survive and thrive under changing seasons. Together with seasonal growth adaptation, dormancy and sprouting are critical factors determining crop yield and market supply, as various geophytes also serve as major food, floriculture, and ornamental crops. Dormancy in such crops determines crop availability in the market, as most of them are consumed during the dormant stage. On the other hand, uniform/maximal sprouting is crucial for maximum yield. Thus, dormancy and sprouting regulation have great economic importance. Dormancy-sprouting cycles in geophytes are regulated by genetic, exogenous (environmental), and endogenous (genetic, metabolic, hormonal, etc.) factors. Comparatively, the temperature is more dominant in regulating dormancy and sprouting in geophytes, unlike above-ground tissues, where both photoperiod and temperature control are involved. Despite huge economic importance, studies concerning the regulation of dormancy and sprouting are scarce in the majority of geophytes. To date, only a few molecular factors involved in the process have been suggested. Recently, omics studies on molecular and metabolic factors involved in dormancy and growth regulation of underground vegetative tissues have provided more insight into the mechanism. Here, we discuss current knowledge of the environmental and molecular regulation and control of dormancy and sprouting in geophytes, and discuss challenges/questions that need to be addressed in the future for crop improvement.