College of Life Sciences, Zhejiang University, Hangzhou 310058, China;
Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712.
Proc Natl Acad Sci U S A. 2021 Nov 23;118(47). doi: 10.1073/pnas.2107541118.
Construction economics of plant roots exhibit predictable relationships with root growth, death, and nutrient uptake strategies. Plant taxa with inexpensively constructed roots tend to more precisely explore nutrient hotspots than do those with costly constructed roots but at the price of more frequent tissue turnover. This trade-off underlies an acquisitive to conservative continuum in resource investment, described as the "root economics spectrum (RES)." Yet the adaptive role and genetic basis of RES remain largely unclear. Different ecotypes of switchgrass () display root features exemplifying the RES, with costly constructed roots in southern lowland and inexpensively constructed roots in northern upland ecotypes. We used an outbred genetic mapping population derived from lowland and upland switchgrass ecotypes to examine the genetic architecture of the RES. We found that absorptive roots (distal first and second orders) were often "deciduous" in winter. The percentage of overwintering absorptive roots was decreased by northern upland alleles compared with southern lowland alleles, suggesting a locally-adapted conservative strategy in warmer and acquisitive strategy in colder regions. Relative turnover of absorptive roots was genetically negatively correlated with their biomass investment per unit root length, suggesting that the key trade-off in framing RES is genetically facilitated. We also detected strong genetic correlations among root morphology, root productivity, and shoot size. Overall, our results reveal the genetic architecture of multiple traits that likely impacts the evolution of RES and plant aboveground-belowground organization. In practice, we provide genetic evidence that increasing switchgrass yield for bioenergy does not directly conflict with enhancing its root-derived carbon sequestration.
植物根系的结构经济学与根系生长、死亡和养分吸收策略表现出可预测的关系。与构建成本高的根系相比，构建成本低的植物类群往往能更精确地探测养分热点，但代价是更频繁的组织更新。这种权衡关系是资源投资中获取性到保守性连续体的基础，被描述为“根系经济谱（RES）”。然而，RES 的适应作用和遗传基础在很大程度上仍不清楚。不同的柳枝稷生态型（）表现出体现 RES 的根系特征，在低地的南部和高地的北部生态型中具有构建成本高的根系和构建成本低的根系。我们利用源自低地和高地柳枝稷生态型的杂交遗传图谱群体来研究 RES 的遗传结构。我们发现，吸收根（远端第一和第二级）在冬季往往是“落叶的”。与低地南部等位基因相比，高地北部等位基因减少了越冬吸收根的比例，这表明在温暖地区存在适应性保守策略，而在寒冷地区则存在更具获取性的策略。吸收根的相对周转率与单位根长的生物量投资呈负相关，这表明在构建 RES 时的关键权衡关系在遗传上是有利的。我们还检测到吸收根形态、根生产力和地上部大小之间存在强烈的遗传相关性。总体而言，我们的研究结果揭示了多个性状的遗传结构，这些性状可能影响 RES 和植物地上-地下组织的进化。实际上，我们提供了遗传证据，表明增加柳枝稷的生物量用于生物能源并不直接与增强其根衍生的碳固存相冲突。
