Comas L, Bouma T, Eissenstat D
Department of Horticulture, The Pennsylvania State University, University Park, PA, 16802, USA.
Plant Physiology and Ecology Intercollege Graduate Programs, The Pennsylvania State University, University Park, PA, 16802, USA.
Oecologia. 2002 Jun;132(1):34-43. doi: 10.1007/s00442-002-0922-8. Epub 2002 Jun 1.
There is an extremely limited understanding of how plants of different potential growth rate vary in root traits, especially in woody species. We contrasted fine root morphology, physiology, and elemental construction between a fast- and a slow-growing species in each of three families: Aceraceae (maple), Fagaceae (oak), and Pinaceae (pine). Measurements were primarily made on 1-year-old seedlings growing in a growth chamber. Across all three families, first- and second-order roots of fast-growing species had greater specific root length, thinner diameters, and faster respiration rates than those of slow-growing species. These fine roots of fast-growing species in Aceraceae and Fagaceae also had faster phosphorus (P) uptake on a surface area basis than those of slow-growing species, whereas little difference in P uptake was found between Pinaceae species. On a dry weight basis, roots of fast-growing species in Aceraceae and Fagaceae had higher nitrogen concentrations, lower carbon:nitrogen ratios and higher tissue construction costs than roots of slow-growing species (data were unavailable for Pinaceae). Tissue density did not vary in a consistent pattern between fast- and slow-growing species across all three families (P=0.169). To better understand the ecological significance of differences in these root characteristics, a root efficiency model was used to compare P uptake and root carbon (C) cost of each species in simulated field situations in two soils, one with low P buffering capacity (loamy sand) and another with relatively high P buffering capacity (silt loam). For the soil conditions modeled, fast-growing species of Aceraceae and Fagaceae were 17-70% more efficient (defined as cumulative P gain divided by cumulative C cost) at nutrient capture than slow-growing species while the fast-growing Pinaceae species was 20-24% less efficient than the slow-growing species. However, among all three families, roots of fast-growing species reached maximum lifetime efficiency 5-120 days sooner, depending on soil type. Thus, modeling results indicated that root traits of fast- and slow-growing species affected P acquisition in simulated field soil although soil type also had a strong impact.
对于不同潜在生长速率的植物在根系性状方面如何变化，尤其是木本植物，人们的了解极为有限。我们对比了三个科（槭树科（枫树）、壳斗科（橡树）和松科（松树））中快速生长和慢速生长物种的细根形态、生理及元素组成。测量主要针对生长在生长室中的一年生幼苗。在所有这三个科中，快速生长物种的一级和二级根比慢速生长物种具有更大的比根长、更细的直径和更快的呼吸速率。槭树科和壳斗科中快速生长物种的这些细根在单位表面积基础上的磷（P）吸收也比慢速生长物种更快，而松科物种之间在磷吸收方面差异不大。以干重计，槭树科和壳斗科中快速生长物种的根比慢速生长物种的根具有更高的氮浓度、更低的碳氮比和更高的组织构建成本（松科的数据不可用）。在所有这三个科中，快速生长和慢速生长物种之间的组织密度没有呈现出一致的变化模式（P = 0.169）。为了更好地理解这些根系特征差异的生态意义，我们使用了一个根系效率模型来比较在两种土壤（一种低磷缓冲能力（壤质砂土），另一种相对高磷缓冲能力（粉质壤土））的模拟田间条件下每个物种的磷吸收和根碳（C）成本。对于所模拟的土壤条件，槭树科和壳斗科的快速生长物种在养分获取方面比慢速生长物种效率高17 - 70%（定义为累积磷增益除以累积碳成本），而快速生长的松科物种比慢速生长物种效率低20 - 24%。然而，在所有这三个科中，快速生长物种的根根据土壤类型，能提前5 - 120天达到最大寿命效率。因此，模型结果表明，快速生长和慢速生长物种的根系性状在模拟田间土壤中影响磷的获取，尽管土壤类型也有很大影响。
