Soluble sugars (e.g. glucose, fructose and sucrose) and starch are the most abundant components of the non-structural carbohydrates (NSCs) stored in woody tissues of the stem and roots. These compounds represent the most abundant C reserves in trees, contributing to plants survival and their resilience to adverse conditions. These compounds are involved in controlling and regulating photosynthate allocation between C supply and demand.
In Mediterranean beech trees, the trade-off of resources allocation between growth and reserves was recognized as a mechanism for counteracting the negative effects of extreme events and improve the resilience of trees. However, the responses to stressful events of NSCs in coarse roots can differ from stems. Despite the recognized importance of NSCs for plant functioning and resilience, little is known regarding their long-term seasonal regulation and trade-offs against growth in forest trees.
Parenchyma fractions are recognized as a proxy for non-structural carbohydrates storage capacity in tree. Our study, evaluated the long-term dynamics of mature tree reserves in stem and root, proxied by parenchyma features, and focusing on the trade off and interplay between the resources allocation in radial growth and reserves in stem. In a Mediterranean beech forest, NSCs content, stem and root wood anatomy analysis, and eddy covariance data, were combined. In beech there is a partitioning in the functional roles of axial and radial parenchyma, different roles of stem and roots in reserves storage. Moreover, our results confirm with anatomical evidences that in case of C source limitation, beech trees prioritize to allocate photosynthate to reserve, over radial growth.