Journal Article

Multiple adaptive responses of Australian native perennial legumes with pasture potential to grow in phosphorus- and moisture-limited environments

Lalith D. B. Suriyagoda, Megan H. Ryan, Michael Renton and Hans Lambers

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 105, issue 5, pages 755-767
Published in print May 2010 | ISSN: 0305-7364
Published online May 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq040
Multiple adaptive responses of Australian native perennial legumes with pasture potential to grow in phosphorus- and moisture-limited environments

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  • Ecology and Conservation
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Background and Aims

Many Australian legumes have evolved in low-phosphorus (P) soils and low-rainfall areas. Therefore a study was made of the interaction of soil [P] and water availability on growth, photosynthesis, water-use efficiency (WUE) and P nutrition of two Australian native legumes with pasture potential, Cullen australasicum and C. pallidum, and the widely grown exotic pasture legume, lucerne (Medicago sativa).

Methods

Plants were grown in a glasshouse at 3, 10 and 30 mg P kg−1 dry soil for 5 months. At week 10, two drought treatments were imposed, total pot dried (all-dry) and only top soil dried (top-dry), while control pots were maintained at field capacity.

Key Results

Shoot dry weight produced by lucerne was never higher than that of C. australasicum. For C. pallidum only, shoot dry weight was reduced at 30 mg P kg−1 dry soil. The small root system of the Cullen species was quite plastic, allowing plants to access P and moisture efficiently. Lucerne always had a higher proportion of its large root system in the top soil layer compared with Cullen species. All species showed decreased photosynthesis, leaf water potential and stomatal conductance when exposed to drought, but the reductions were less for Cullen species, due to tighter stomatal control, and consequently they achieved a higher WUE. All species showed highest rhizosphere carboxylate concentrations in the all-dry treatment. For lucerne only, carboxylates decreased as P supply increased. Citrate was the main carboxylate in the control and top-dry treatments, and malate in the all-dry treatment.

Conclusions

Multiple adaptive responses of Cullen species and lucerne favoured exploitation of low-P soils under drought. The performance of undomesticated Cullen species, relative to that of lucerne, shows their promise as pasture species for environments such as in south-western Australia where water and P are limiting, especially in view of a predicted drying and warming climate.

Keywords: Australian native legumes; carboxylates; climate change; Cullen spp.; drought; Medicago sativa; novel crops; perennial pastures; phosphorus; photosynthesis; root distribution; water-use efficiency

Journal Article.  10002 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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