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Phosphorus deficiency affects the allocation of below-ground resources to combined cluster roots and nodules in Lupinus albus
Author
Rochelle Thuynsma, Alex Valentine and Aleysia Kleinert
Year
2013
Journal Title
Journal of Plant Physiology
Institution
Elsevier GmbH.
Volume
171
Issue
3-4
Pages
285–291
Call Number
JA0557-14
Keywords
Cluster roots; Nodules; Phosphorus deficiency; Resource allocation; White lupin
Abstract:
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.
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