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Plant function and evolutionary biology
RESEARCH ARTICLE

Linking root traits to superior phosphorus uptake and utilisation efficiency in three Fabales in the Core Cape Subregion, South Africa

Dunja MacAlister A , A. Muthama Muasya A and Samson B. M. Chimphango A B
+ Author Affiliations
- Author Affiliations

A Department of Biological Sciences, HW Pearson Building, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa.

B Corresponding author. Email: samson.chimphango@uct.ac.za

Functional Plant Biology 45(7) 760-770 https://doi.org/10.1071/FP17209
Submitted: 29 November 2016  Accepted: 24 January 2018   Published: 20 February 2018

Abstract

In the low-P soil of the fynbos biome, plants have evolved several morphological and physiological P acquisition and use mechanisms, leading to variable uptake and use efficiencies. We expected that plants grown in low-P soils would exhibit greater P acquisition traits and hypothesised that Aspalathus linearis (Burm. f.) R. Dahlgren, a cluster-root-forming species adapted to drier and infertile soils, would be the most efficient at P acquisition compared with other species. Three fynbos Fabales species were studied: A. linearis and Podalyria calyptrata (Retz.) Willd, both legumes, and Polygala myrtifolia L., a nonlegume. A potted experiment was conducted where the species were grown in two soil types with high P (41.18 mg kg–1) and low P (9.79 mg kg–1). At harvest, biomass accumulation, foliar nutrients and P acquisition mechanisms were assessed. Polygala myrtifolia developed a root system with greater specific root length, root hair width and an average root diameter that exuded a greater amount of citrate and, contrary to the hypothesis, exhibited greater whole-plant P uptake efficiency. However, P. calyptrata had higher P use efficiency, influenced by N availability through N2 fixation. Specific root length, root length and root:shoot ratio were promising morphological traits for efficient foraging of P, whereas acid phosphatase exudation was the best physiological trait for solubilisation of P.

Additional keywords: Aspalathus linearis, P acquisition, Podalyria calyptrata, Polygala myrtifolia, root morphology.


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