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Type: Journal article
Title: Xylomelum occidentale (Proteaceae) accesses relatively mobile soil organic phosphorus without releasing carboxylates
Author: Zhong, H.
Zhou, J.
Azmi, A.
Arruda, A.J.
Doolette, A.L.
Smernik, R.J.
Lambers, H.
Citation: Journal of Ecology, 2021; 109(1):246-259
Publisher: British Ecological Society; Wiley
Issue Date: 2021
ISSN: 0022-0477
Statement of
Hongtao Zhong, Jun Zhou, Azrul Azmi, André J. Arruda, Ashlea L. Doolette, Ronald J. Smernik, Hans Lambers
Abstract: 1. Hundreds of Proteaceae species in Australia and South Africa typically grow on phosphorus (P)-impoverished soils, exhibiting a carboxylate-releasing P-mobilizing strategy. In the Southwest Australian Biodiversity Hotspot, two Xylomelum (Proteaceae) species are widely distributed, but restricted within that distribution. 2. We grew Xylomelum occidentale in hydroponics at 1 μM P. Leaves, seeds, rhizosheath and bulk soil were collected in natural habitats. 3. Xylomelum occidentale did not produce functional cluster roots and occupied soils that are somewhat less P-impoverished than those in typical Proteaceae habitats in the region. Based on measurements of foliar manganese concentrations (a proxy for rhizosphere carboxylate concentrations) and P fractions in bulk and rhizosheath soil, we conclude that X. occidentale accesses organic P, without releasing carboxylates. Solution 31P-NMR spectroscopy revealed which organic P forms X. occidentale accessed. 4. Xylomelum occidentale uses a strategy that differs fundamentally from that t ypical in Proteaceae, accessing soil organic P without carboxylates. We surmise that this novel strategy is likely expressed also in co-occurring non-Proteaceae that lack a carboxylate- exuding strategy. These co-occurring species are unlikely to benefit from mycorrhizal associations, because plant-available soil P concentrations are too low. 5. Synthesis. Our findings show the first field evidence of effectively utilizing soil organic P by X. occidentale without carboxylate exudation and explain their relatively restricted distribution in an old P-impoverished landscape, contributing to a better understanding of how diverse P-acquisition strategies coexist in a megadiverse ecosystem.
Keywords: Carboxylates; ecophysiology; manganese; phosphatases; Proteaceae; soil organic P; solution ³¹P-NMR; Xylomelum
Rights: 2020 British Ecological Society
DOI: 10.1111/1365-2745.13468
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