Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; World Agroforestry Centre, East Asia Node, 132 Lanhei Rd, Kunming 650201, China.
J Plant Physiol. 2014 Feb 15;171(3-4):285-91. doi: 10.1016/j.jplph.2013.09.001. Epub 2013 Oct 13.
Lupins can rely on both cluster roots and nodules for P acquisition and biological nitrogen fixation (BNF), respectively. The resource allocation (C, N and P) between cluster roots and nodules has been largely understudied during P-deficient conditions. The aim of this investigation was therefore to determine the changes in resource allocation between these organs during fluctuations in P supply. Lupinus albus was cultivated in sand culture for 3 weeks, with either sufficient (2 mM high) or limiting (0.1 mM low) P supply. Although variation on P supply had no effect on the total biomass, there were significant differences in specialised below-ground organ allocation to cluster roots and nodule formation. Cluster root formation and the associated C-costs increased during low P supply, but at sufficient P-supply the construction and growth respiration costs of cluster roots declined along with their growth. In contrast to the cluster root decline at high P supply, there was an increase in nodule growth allocation and corresponding C-costs. However, this was not associated with an increase in BNF. Since cluster roots were able to increase P acquisition under low P conditions, this below-ground investment may also have benefited the P nutrition of nodules. These findings provide evidence that when lupins acquire N via BNF in their nodules, there may be a trade-off in resource allocation between cluster roots and nodules.
羽扇豆可以分别依靠簇状根和根瘤来获取磷和进行生物固氮（BNF）。在磷缺乏条件下，簇状根和根瘤之间的资源分配（C、N 和 P）在很大程度上研究不足。因此，本研究旨在确定在磷供应波动期间这些器官之间资源分配的变化。将白羽扇豆在沙培中培养 3 周，用充足（2 mM 高）或有限（0.1 mM 低）的磷供应。尽管磷供应的变化对总生物量没有影响，但对簇状根和根瘤形成的专门地下器官分配有显著差异。在低磷供应下，簇状根的形成及其相关的 C 成本增加，但在充足的磷供应下，簇状根的结构和生长呼吸成本随着其生长而下降。与高磷供应下簇状根的减少形成对比的是，根瘤生长分配和相应的 C 成本增加。然而，这与 BNF 的增加无关。由于簇状根能够在低磷条件下增加磷的获取，这种地下投资也可能有益于根瘤的磷营养。这些发现表明，当羽扇豆通过根瘤中的 BNF 获得氮时，簇状根和根瘤之间可能存在资源分配的权衡。
