Department of Horticulture, The Pennsylvania State University, University Park, Pennsylvania 16802 USA.
Am J Bot. 2008 Dec;95(12):1506-14. doi: 10.3732/ajb.0800092. Epub 2008 Nov 7.
Understanding root processes at the whole-plant or ecosystem scales requires an accounting of the range of functions within a root system. Studying root traits based on their branching order can be a powerful approach to understanding this complex system. The current study examined the highly branched root system of the ericoid plant, Vaccinium corymbosum L. (highbush blueberry) by classifying its root orders with a modified version of the morphometric approach similar to that used in hydrology for stream classification. Root anatomy provided valuable insight into variation in root function across orders. The more permanent portion of the root system occurred in 4th- and higher-order roots. Roots in these orders had radial growth; the lowest specific root length, N:C ratios, and mycorrhizal colonization; the highest tissue density and vessel number; and the coarsest root diameter. The ephemeral portion of the root system was mainly in the first three root orders. First- and 2nd-order roots were nearly anatomically identical, with similar mycorrhizal colonization and diameter, and also, despite being extremely fine, median lifespans were not very short (115-120 d; estimated with minirhizotrons). Our research underscores the value of examining root traits by root order and its implications to understanding belowground processes.
理解整个植物或生态系统尺度的根系过程需要对根系系统内的各种功能进行核算。基于分支顺序研究根系特征可以成为理解这一复杂系统的有力方法。本研究通过对类似水文学中用于溪流分类的形态计量方法进行修改，对越橘属植物（高丛蓝莓）的高度分枝的根系系统进行了分类，以此来研究其根系顺序。根系解剖结构为研究不同根系顺序的功能变化提供了有价值的见解。根系系统中更持久的部分存在于第 4 级及更高等级的根系中。这些等级的根系具有径向生长；最低的比根长、N:C 比和菌根定殖率；最高的组织密度和导管数量；以及最粗的根直径。根系系统的短暂部分主要存在于前三个根系顺序中。第 1 级和第 2 级根系在解剖结构上几乎完全相同，具有相似的菌根定殖率和直径，而且尽管非常细，但中值寿命并不很短（115-120d；用微根窗估计）。我们的研究强调了按根系顺序研究根系特征的价值及其对理解地下过程的意义。
