Department of Ecology and Evolutionary Biology, Unit-3043, 75 N. Eagleville Road, University of Connecticut, Storrs, Connecticut 06269-3043 USA.
Am J Bot. 2009 Aug;96(8):1388-98. doi: 10.3732/ajb.0800237. Epub 2009 Jul 10.
Wood density plays a key role in ecological strategies and life history variation in woody plants, but little is known about its anatomical basis in shrubs. We quantified the relationships between wood density, anatomy, and climate in 61 shrub species from eight field sites along latitudinal belts between 31° and 35° in North and South America. Measurements included cell dimensions, transverse areas of each xylem cell type and percentage contact between different cell types and vessels. Wood density was more significantly correlated with precipitation and aridity than with temperature. High wood density was achieved through reductions in cell size and increases in the proportion of wall relative to lumen. Wood density was independent of vessel traits, suggesting that this trait does not impose conduction limitations in shrubs. The proportion of fibers in direct contact with vessels decreased with and was independent of wood density, indicating that the number of fiber-vessel contacts does not explain the previously observed correlation between wood density and implosion resistance. Axial and radial parenchyma each had a significant but opposite association with wood density. Fiber size and wall thickness link wood density, life history, and ecological strategies by controlling the proportion of carbon invested per unit stem volume.
木材密度在木本植物的生态策略和生活史变异中起着关键作用，但人们对灌木的解剖学基础知之甚少。我们在北美洲和南美洲 31°至 35°纬度带的 8 个野外站点的 61 种灌木物种中，量化了木材密度、解剖结构和气候之间的关系。测量包括细胞尺寸、每种木质部细胞类型的横截面积以及不同细胞类型和导管之间的接触百分比。木材密度与降水和干旱的相关性大于与温度的相关性。通过减小细胞尺寸和增加壁相对于腔的比例来实现高木材密度。木材密度与导管特征无关，这表明该特征不会对灌木的传导造成限制。与导管直接接触的纤维比例随着木材密度的增加而减少且与木材密度无关，这表明纤维-导管接触的数量并不能解释先前观察到的木材密度与内爆阻力之间的相关性。轴向和径向薄壁组织都与木材密度有显著的但相反的关联。纤维大小和细胞壁厚度通过控制每单位茎体积投入的碳的比例，将木材密度、生活史和生态策略联系起来。
