Non-structural carbohydrate storage strategy in trunk tissues of different wood porosity species in warm temperate...

Wood porosity types (non-porous, diffuse-porous, and ring-porous) reflect evolutionary gradients cha-racteristics of xylem anatomy of temperate tree species. The mechanisms linking porosity type to non-structural carbohydrate (NSC) storage strategy in stem tissues remain unclear. We conducted an experiment with 77 warm-tempe-rate tree species in the Baotianman National Nature Reserve, Henan Province. Among the examined species, there were 3 non-porous wood species, 45 diffuse-porous wood species, and 29 ring-porous wood species (including semi-ring-porous wood). We measured soluble sugars, starch, total NSC concentrations and sugars/starch ratio in bark, sapwood, and heartwood at breast height to explore the influence of wood porosity on NSC storage strategy across stem tissues (bark, sapwood and heartwood). The results showed that the types of trunk tissue and wood porosity had significant effects on the concentration of NSC and its components (soluble sugars, and starch). As for the trunk cross-section, NSC and its components exhibited an inward decline trend, with total NSC concentration in bark (6.4%) being notably higher than that in sapwood (3.2%) and heartwood (2.5%). The total NSC in various trunk tissues was dominant in the form of soluble sugars. Across the three wood porosity types, the concentrations of soluble sugars, total NSC, and sugars/starch ratio in tree bark displayed a counter-evolutionary sequence pattern (non-porous > diffuse-porous > ring-porous), while that in sapwood and heartwood increased along the evolutionary gradient. The concentrations of NSC and its components in sapwood and that in heartwood were significantly correlated for both diffuse-porous and ring-porous tree species. Soluble sugars and starch exhibited significant positive correlations in bark of non-porous and diffuse-porous trees and the three trunk tissues of ring-porous tree species. Along the evolutionary gradient of wood porosity, warm-temperate trees tended to optimize resource allocation by reducing the NSC concentration from bark to sapwood and enhancing the functional differentiation between sapwood and heartwood, reflecting the coordination between xylem anatomical structure and storage function.