Phosphorus deficiency affects the allocation of below-ground resources to combined cluster roots and nodules in Lupinus albus |
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Institution: | 1. Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa;2. World Agroforestry Centre, East Asia Node, 132 Lanhei Rd, Kunming 650201, China |
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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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Keywords: | Cluster roots Nodules Phosphorus deficiency Resource allocation White lupin P Max"} {"#name":"keyword" "$":{"id":"kw0035"} "$$":[{"#name":"text" "_":"maximum rate of photosynthesis PNUE"} {"#name":"keyword" "$":{"id":"kw0045"} "$$":[{"#name":"text" "_":"photosynthetic nitrogen use efficiency PPUE"} {"#name":"keyword" "$":{"id":"kw0055"} "$$":[{"#name":"text" "_":"photosynthetic phosphate use efficiency %NDFA"} {"#name":"keyword" "$":{"id":"kw0065"} "$$":[{"#name":"text" "_":"nitrogen derived from atmosphere RGR"} {"#name":"keyword" "$":{"id":"kw0075"} "$$":[{"#name":"text" "_":"relative growth rates SNAR"} {"#name":"keyword" "$":{"id":"kw0085"} "$$":[{"#name":"text" "_":"specific nitrogen acquisition rate SNUR"} {"#name":"keyword" "$":{"id":"kw0095"} "$$":[{"#name":"text" "_":"specific nitrogen utilisation rate SPAR"} {"#name":"keyword" "$":{"id":"kw0105"} "$$":[{"#name":"text" "_":"specific phosphate acquisition rate SPUR"} {"#name":"keyword" "$":{"id":"kw0115"} "$$":[{"#name":"text" "_":"specific phosphate utilisation rate |
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