Global variation in nonstructural carbohydrate stores in response to climate

Abstract

Woody plant species store nonstructural carbohydrates (NSCs) for many functions. While known to buffer against fluctuations in photosynthetic supply, such as at night, NSC stores are also thought to buffer against environmental extremes, such as drought or freezing temperatures by serving as either back‐up energy reserves or osmolytes. However, a clear picture of how NSCs are shaped by climate is still lacking. Here, we update and leverage a unique global database of seasonal NSC storage measurements to examine whether maximum total NSC stores and the amount of soluble sugars are associated with clinal patterns in low temperatures or aridity, indicating they may confer a benefit under freezing or drought conditions. We examine patterns using the average climate at each study site and the unique climatic conditions at the time and place in which the sample was taken. Altogether, our results support the idea that NSC stores act as critical osmolytes. Soluble Sugars increase with both colder and drier conditions in aboveground tissues, indicating they can plastically increase a plants' tolerance of cold or arid conditions. However, maximum total NSCs increased, rather than decreased, with average site temperature and had no relationship to average site aridity. This result suggests that the total amount of NSC a plant stores may be more strongly determined by its capacity to assimilate carbon than by environmental stress. Thus, NSCs are unlikely to serve as reservoir of energy. This study is the most comprehensive synthesis to date of global NSC variation in relation to climate and supports the idea that NSC stores likely serve as buffers against environmental stress. By clarifying their role in cold and drought tolerance, we improve our ability to predict plant response to environment.

Climate warming could free cold‐adapted trees from C‐conservative allocation strategy of storage over growth

“…Although our study could not provide conclusive molecular evidence, this outcome might be attributable to local adaptation of C allocation among various sinks under long‐term low temperature suppression. The ability to evolve higher NSC concentration may confer the trees an enhanced resilience during the times of environmental stress by serving as a back‐up fuel source or osmotic reservoir (Blumstein, Gersony, et al., 2022).…”

“…For instance, trees at their upper elevational limits always employ available photosynthates most strategically to maximize development while avoiding stress (Cong et al., 2022; Piper, 2021). On the one hand, trees maintain a larger pool of stored C, whose osmotically active, soluble component plays a crucial role not only in preserving cell turgor but also in keeping vascular integrity (xylem and phloem), enhancing long‐term cryoprotective functions (Blumstein, Gersony, et al., 2022; Long & Adams, 2023). On the other hand, the accumulation of osmotically inactive starch towards upper elevation limit has been interpreted as a result of imbalance between C source and C sink activities induced by low temperature (Hoch & Körner, 2012).…”

Nonstructural carbohydrate dynamics' relationship to leaf development under varying environments

“…68% – resided in sugars rather than starch at the onset of our experiment (8 January 2022; Stage 0). This finding is in line with several studies that have examined NSC patterns over seasonal time scales and found starch concentrations to be lowest in winter (Klein et al ., 2016; Martínez‐Vilalta et al ., 2016; Furze et al ., 2019) and when temperatures reach extreme minimums (Blumstein & Hopkins, 2021; Blumstein et al ., 2022).…”

Carbohydrate dynamics in Populus trees under drought: An expression atlas of genes related to sensing, translocation, and metabolism across organs

“…Although NSCs have been suggested to function as a backup energy reserve during the inhibition of carbohydrate production in response to drought, other studies have indicated that NSCs may play a pivotal role in osmoregulation. A recent analysis of a large database showed that higher concentrations of total NSCs are not necessarily associated with site aridity and suggested that NSCs likely function in osmoregulation rather than in energy reserves (Blumstein et al, 2023). Poplar trees respond to drought by reducing total NSC content and increasing the concentration of sucrose, glucose, and fructose, which are the main sugars that operate during the dry season (Regier et al, 2009; Regier et al, 2010).…”