Variation in morphological and physiological parameters in herbaceous perennial legumes in response to phosphorus supply
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Change in morphological and physiological parameters in response to phosphorus (P) supply was studied in 11 perennial herbaceous legume species, six Australian native (Lotus australis, Cullen australasicum, Kennedia prorepens, K. prostrata, Glycine canescens, C. tenax) and five exotic species (Medicago sativa, Lotononis bainesii, Bituminaria bituminosa var albomarginata, Lotus corniculatus, Macroptilium bracteatum). We aimed to identify mechanisms for P acquisition from soil. Plants were grown in sterilised washed river sand; eight levels of P as KH2PO4 ranging from 0 to 384 μg P g−1 soil were applied. Plant growth under low-P conditions strongly correlated with physiological P-use efficiency and/or P-uptake efficiency. Taking all species together, at 6 μg P g−1 soil there was a good correlation between P uptake and both root surface area and total root length. All species had higher amounts of carboxylates in the rhizosphere under a low level of P application. Six of the 11 species increased the fraction of rhizosphere citrate in response to low P, which was accompanied by a reduction in malonate, except L. corniculatus. In addition, species showed different plasticity in response to P-application levels and different strategies in response to P deficiency. Our results show that many of the 11 species have prospects for low-input agroecosystems based on their high P-uptake and P-use efficiency.
KeywordsCarboxylate exudation Native Australian legumes Perennial herbaceous legume Phosphorus Rhizosphere pH Root diameter Specific root length Root surface area Total root length
This research was supported by the Australian Research Council (ARC), the Department of Agricultural and Food Western Australia, Heritage Seeds, the Chemistry Centre of Western Australia, and the Facey Group and Mingenew Irvin Group. We thank Dr Daniel Real, Mr Richard Snowball and Dr Ron Yates (DAFWA), Mr Steve Hughes (SARDI), and Mr Leonard Song (Heritage Seeds) for providing legume seeds and rhizobia, Dr Clinton Revell and Mr Richard Bennett for technical advice, and Ms Tammy Edmonds-Tibbett and Mr Tim Morald for technical help.
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