Zhang Guangqi, Mao Zhun, Fortunel Claire, Martínez-Vilalta Jordi, Viennois Gaëlle, Maillard Pascale, Stokes Alexia
AMAP, Univ Montpellier, CIRAD, CNRS, INRAE, IRD, 34000 Montpellier, France.
CREAF, E08193 Bellaterra (Cerdanyola del Vallès), Catalonia, Spain.
Am J Bot. 2022 Apr;109(4):535-549. doi: 10.1002/ajb2.1838. Epub 2022 Apr 8.
Nonstructural carbohydrates (NSCs) play a key role in tree performance and functioning and are stored in radial and axial parenchyma (RAP) cells. Whether this relationship is altered among species and climates or is linked to functional traits describing xylem structure (wood density) and tree stature is not known.
In a systematic review, we collated data for NSC content and the proportion of RAP in stems for 68 tree species. To examine the relationships of NSCs and RAP with climatic factors and other functional traits, we also collected climatic data at each tree's location, as well as wood density and maximum height. A phylogenetic tree was constructed to examine the influence of species' evolutionary relationships on the associations among NSCs, RAP, and functional traits.
Across all 68 tree species, NSCs were positively correlated with RAP and mean annual temperature, but relationships were only weakly significant in temperate species and angiosperms. When separating RAP into radial parenchyma (RP) and axial parenchyma (AP), both NSCs and wood density were positively correlated with RP but not with AP. Wood in taller trees was less dense and had lower RAP than in shorter trees, but height was not related to NSCs.
In trees, NSCs are stored mostly in the RP fraction, which has a larger surface area in warmer climates. Additionally, NSCs were only weakly linked to wood density and tree height. Our analysis of evolutionary relationships demonstrated that RAP fractions and NSC content were always closely related across all 68 tree species, suggesting that RAP can act as a reliable proxy for potential NSC storage capacity in tree stems.
非结构性碳水化合物（NSCs）在树木的性能和功能中起关键作用，并储存在径向和轴向薄壁组织（RAP）细胞中。目前尚不清楚这种关系在不同物种和气候条件下是否会发生变化，或者是否与描述木质部结构（木材密度）和树高的功能性状相关。
在一项系统综述中，我们整理了68种树木的NSC含量和茎中RAP比例的数据。为了研究NSCs和RAP与气候因素及其他功能性状之间的关系，我们还收集了每棵树所在位置的气候数据，以及木材密度和最大树高。构建了系统发育树，以检验物种进化关系对NSCs、RAP和功能性状之间关联的影响。
在所有68种树木中，NSCs与RAP和年平均温度呈正相关，但在温带物种和被子植物中，这种关系仅具有微弱的显著性。当将RAP分为径向薄壁组织（RP）和轴向薄壁组织（AP）时，NSCs和木材密度均与RP呈正相关，而与AP无关。较高树木的木材密度较低，RAP也比矮树低，但树高与NSCs无关。
在树木中，NSCs主要储存在RP部分，该部分在温暖气候下具有更大的表面积。此外，NSCs与木材密度和树高的关联较弱。我们对进化关系的分析表明，在所有68种树木中，RAP部分和NSC含量始终密切相关，这表明RAP可以作为树木茎干中潜在NSC储存能力的可靠指标。
