Abstract
Woody perennials’ reliance on nonstructural carbohydrates (NSC) reserves for the resumption of spring growth necessitates an accumulation of NSC prior to dormancy. It is assumed that during dormancy temperature-regulated biological activities gauge the progression of winter and affect the metabolic rates and physiology of NSC reserves. Thus, changes in temperature signal the arrival of spring and determine the amount of reserves available for growth resumption. As woody perennials are dependent on dispersed storage of NSC during spring, they need an integrated remobilization and redistribution for synchronous and effective development of photosynthetic and reproductive organs. However, it is not known how storage compartments interact at the whole plant level, when NSC reserves are mobilized, or how local and distal storage compartments influence the biology of spring growth resumption. The goal of this mini-review is to shift the focus of winter biology from bud-centric to the whole plant. We discuss winter NSC management in the context of climate change with a special emphasis on how projected mild winters may affect the carbon budget, transport, and allocation during winter. We look at three aspects of NSC regulation underlying dormancy (I) the molecular regulation of dormancy (II) temperature dependent winter NSC metabolism, and (III) spring NSC remobilization and redistribution processes.
Highlights
The perennial habit in mediterranean, boreal, and temperate climates necessitates overwintering
Due to the prevailing assumption of phloem dormancy and the distinctive occurrence of sugar accumulation in its sap during bud break, xylem has been proposed as the primary path for long-distance nonstructural carbohydrates (NSC) transport (Campbell and Strother, 1996)
The accumulation of sugars in xylem sap in response to low temperatures may take part in the transport of NSC, especially when considering thermal gradients at the whole plant scale in spring when roots are colder than the canopy (Zwieniecki et al, 2015)
Summary
The perennial habit in mediterranean, boreal, and temperate climates necessitates overwintering. In order to provide this needed energy, NSC are stored in parenchyma cells of wood and roots before winter, ensuring survival, and later remobilized to support bud-break and growth resumption in the spring (Figure 1) (Loescher et al, 1990; Barbaroux and Bréda, 2002; Richardson et al, 2013; Rosas et al, 2013) This dormancy period is inadequately understood at the mechanistic level which limits our ability to build robust phenology models and understand the role of NSC in the resilience of perennials to stresses, especially at limits of species range (Bansal and Germino, 2008, 2010). The analysis of the molecular dialogue between buds and storage sites (stems and root) during dormancy and dormancy breaking, and gene expression patterns at the whole plant level, would be important milestones for the mechanistic understanding of dormancy
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