Vessel diameter is related to amount and spatial arrangement of axial parenchyma in woody angiosperms

Parenchyma (薄壁组织) represents a critically important living tissue in the sapwood (边材) of the secondary xylem of woody angiosperms. Considering various interactions between parenchyma and water transporting vessels (导管), we hypothesize a structure–function relationship between both cell types. Through a generalized additive mixed model (广义可加混合模型) approach based on 2,332 woody angiosperm species derived from the literature, we explored the relationship between the proportion and spatial distribution of ray and axial parenchyma (射线和轴向薄壁细胞) and vessel size, while controlling for maximum plant height and a range of climatic factors (气候因子). When factoring in maximum plant height, we found that with increasing mean annual temperatures (平均年均气温), mean vessel diameter (平均导管直径) showed a positive correlation with axial parenchyma proportion and arrangement (排列), but not for ray parenchyma. Species with a high axial parenchyma tissue fraction tend to have wide vessels, with most of the parenchyma packed around (聚集...周围) vessels, whereas species with small diameter vessels show a reduced amount of axial parenchyma that is not directly connected to vessels. This finding provides evidence for independent functions of axial parenchyma and ray parenchyma in large vesselled species and further supports a strong role for axial parenchyma in long-distance xylem water transport.

薄壁组织是木本植物中次生木质部边材中至关重要的活组织。考虑到薄壁组织和水分运输导管之间多方面的互作，作者假设在这两种细胞类型之间存在结构性的功能联系。基于2,332个木本被子植物，通过广义可加混合模型作者研究了射线和轴向薄壁细胞比例和空间分布与导管大小的关系，同时控制最大植株高度和一些列的气候因子。当把最大植株高度作为因子是，作者发现平均年均气温增加的同时，平均导管直径与轴向薄壁细胞的比例和排列呈现正相关，而和射线薄壁细胞则没有相关性。具有高的轴向薄壁细胞片段倾向于更宽的导管，同时大多数的轴向薄壁细胞会聚集在导管的周围，而具有小直径导管的物种轴向薄壁细胞相对减少，同时也不与导管直接相连。本文的发现显示在具有导管的物种中，轴向薄壁细胞与射线薄壁细胞具有独立的功能，并且进一步证明了轴向薄壁细胞在长距离木质部水分运输中的作用。

通讯：Hugh Morris (https://www.uni-ulm.de/nawi/sysbot/prof-dr-steven-jansen/doktoranden/morris/)

个人简介：2001 - 2005年，中央兰开夏大学，学士，方向：树艺学；2006 – 2007年，英国爱丁堡大学、皇家植物园，硕士，方向：生物多样性和植物分类；2011- 2012年，英国布莱顿大学，高等教育研究生；2013- 2016年，乌尔姆大学，博士，方向：植物生物学。

doi: 10.1111/pce.13091