Abstract：
Wood performs several functions to ensure tree survival and carbon allocation to a finite stem volume leads to trade-offs among cell types. It is not known to what extent these trade-offs modify functional trade-offs and if they are consistent across climates and evolutionary lineages. Twelve wood traits were measured in stems and coarse roots across 60 adult angiosperm tree species from temperate, Mediterranean and tropical climates. Regardless of climate, clear trade-offs occurred among cellular fractions, but did not translate into specific functional trade-offs. Wood density was negatively related to hydraulic conductivity (Kth ) in stems and roots, but was not linked to nonstructural carbohydrates (NSC), implying a functional trade-off between mechanical integrity and transport but not with storage. NSC storage capacity was positively associated with Kth in stems and negatively in roots, reflecting a potential role for NSC in the maintenance of hydraulic integrity in stems but not in roots. Results of phylogenetic analyses suggest that evolutionary histories cannot explain covariations among traits. Trade-offs occur among cellular fractions, without necessarily modifying trade-offs in function. However, functional trade-offs are driven by coordinated changes among xylem cell types depending on the dominant role of each cell type in stems and roots.
摘要：
木材执行多种功能，以确保树木的生存和碳分配到有限的茎体积导致细胞类型之间的权衡。尚不清楚这些权衡在多大程度上改变了功能权衡，以及它们在气候和进化谱系之间是否一致。在来自温带的60个成年被子植物树种的茎和粗根中测量了12个木材性状，地中海和热带气候。无论气候如何,细胞部分之间发生了明确的权衡，但没有转化为特定的功能权衡。木材密度与茎和根的导水率（Kth）呈负相关，但与非结构性碳水化合物（NSC）无关，这意味着机械完整性和运输之间的功能权衡，但不与存储。NSC的储存量与茎中的Kth呈正相关，与根中的Kth呈负相关，反映了NSC在维护茎而不是根的水力完整性方面的潜在作用。系统发育分析的结果表明，进化史无法解释性状之间的协变。权衡发生在细胞部分之间，而不一定要修改功能上的权衡。然而,功能权衡是由木质部细胞类型之间的协调变化驱动的，这取决于每种细胞类型在茎和根中的主导作用。
