Root system topology and diameter distribution of species from habitats differing in inundation frequency
Root system topology and diameter distribution of species from habitats differing in inundation frequency
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DOI：
10.1046/j.1365-2435.2001.00523.x
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发表时间：
2001-06-01
影响因子：
5.2
通讯作者：
Koutstaal, B
中科院分区：
文献类型：
--
作者：
Bouma, TJ;Nielsen, KL;Koutstaal, B
1.我们比较了7种盐生植物的根系发生在不同海拔的盐沼，以（i）测试的假设，即根系结构的变化反映了适应淹没频率或氮限制，和（ii）验证理论预测的根直径，链接大小和根拓扑结构之间的关系。沿沿着根轴测定了各分枝的直径和长度，并通过计算拓扑指数（TI）对分枝模式进行了量化.藜科（一年生双子叶植物）的研究表明，随着海拔的升高，个体一级分枝的分支密度和长度有增加的趋势，从而使主轴的相对长度减小。低海拔藜科植物的根分枝呈人字形，而高海拔藜科植物的根分枝方式复杂，其根分枝的TI较小.禾本科植物也表现出随海拔升高个体茎长增加的趋势。然而，TI与海拔高度无关，并不表明所有物种的人字形结构，并在同一范围内的藜科。由于藜科植物的根拓扑结构与海拔高度有关，而禾本科植物的根拓扑结构与海拔高度无关，因此拓扑结构并不一定是所有栖息于盐沼的植物家族的重要适应性状。短的一阶和二阶盐度可能代表了对频繁淹没的更普遍的建筑适应，较长的一阶盐度有利于营养竞争。如果根分枝呈鱼骨状（TI接近1），则根基部直径趋于减小。一级根约为主轴直径的三分之一，二级根约为一级根直径的一半。这些比率说明了使用发育片段排序系统描述根的价值。理论预测的根直径和连接大小之间的关系并不存在于单个根级中，而当结合不同根级时，直径确实随大小缓慢增加.在没有一个明确的根直径和链接大小之间的关系，预测的高碳成本与人字形根系消失，而最小化根间竞争的优势仍然存在。因此，就单位碳投入获得的营养而言，人字形根系将是最有效的。然而，二叉根系提供了更大的潜力，探索土壤，这有助于植物生长在营养有限的栖息地的潜在竞争力。
1. We compared the root systems of seven halophytic species that occur at different elevations on a salt marsh, in order to (i) test the hypothesis that variations in root system architecture reflect adaptation to inundation frequency or nitrogen limitation, and (ii) verify the theoretically predicted relationships between root diameter, link magnitude and root topology. Diameters and lengths of individual laterals were determined along root axes, and branching patterns were quantified by calculating a topological index (TI).2. Chenopodiaceae (annual dicots) showed that with increasing elevation, the branch density and length of individual first-order laterals tended to increase, so that the relative length of the main axes decreased. Root branching of the Chenopodiaceae at lower elevations was herringbone-like, whereas species from higher elevations had smaller TIs because their branching patterns were more complex.3. The Gramineae, too, showed a tendency to increased length of individual laterals with increasing elevation. However, TI was not related to elevation, did not indicate a herringbone structure for all species, and was within the same range of that of the Chenopodiaceae.4. As root topology of the Chenopodiaceae is related to elevation, but that of the grasses is not, topology is not necessarily an important adaptive trait in all plant families that inhabit the salt marsh. Short first- and second-order laterals may represent a more general architectural adaptation to frequent inundation, with longer first-order laterals being favourable to competition for nutrients.5. Diameters at the root base tended to decrease if root branching was herringbone-like (TI close to 1). Roots of first-order laterals were approximately one-third of the diameter of the main axes; second-order laterals were approximately half the diameter of the first-order laterals. These ratios illustrate the value of using the developmental segment-ordering system in describing roots. The theoretically predicted relationship between root diameter and link magnitude was not present within individual orders of roots, whereas diameter did slowly increase with magnitude when combining different root orders.6. In the absence of a clear relationship between root diameter and link magnitude, the predicted high carbon costs associated with herringbone root systems disappear, whereas the advantage of minimized inter-root competition remains. Consequently, herringbone root systems will be most efficient in terms of nutrients gained per carbon invested. However, dichotomous root systems offer a greater potential for exploring the soil, which contributes to the potential competitiveness of plants growing in nutrient limited habitats.