Dynamics of nonstructural carbohydrates during drought and subsequent recovery: A global meta-analysis

The role of carbon starvation in drought-induced plant mortality remains a topic of debate. This underscores the need for a comprehensive understanding of the regulation of non-structural carbohydrates (NSCs) during drought and subsequent recovery. To this end, we compiled 226 articles and conducted a meta-analysis to examine the responses of NSCs to drought and rewatering, as well as the influences of plant functional type, drought magnitude, duration and climate variables. Overall, drought primarily reduced NSC concentrations in leaves, with negligible impacts on stems and roots. While starch concentrations declined, soluble sugar concentrations, including fructose and glucose, increased. Leaf NSC concentration returned to control levels after rewatering, whereas reductions in NSC concentrations in stems and roots were observed in the post-drought period. Herbaceous plants exhibited greater changes in leaf and root soluble sugar concentrations compared to woody plants. Gymnosperms experienced more significant root NSC reductions than angiosperms. Unlike deciduous angiosperms, evergreen angiosperms showed decreases in stem and root NSC concentrations during drought. Starch concentrations in mature woody plants remained relatively stable during drought, whereas they decreased in seedlings and saplings. The negative effects of drought on stem and root starch concentrations diminished with prolonged drought. Increases in soluble sugar concentrations in leaves were more pronounced in drier environments. These findings highlight the complex dynamics of NSCs during drought and subsequent recovery, emphasizing the need to consider plant functional types, drought characteristics, and climatic conditions when assessing the role of carbon starvation in drought-induced plant mortality.