Effects of phosphorus supply on growth, phosphate concentration and cluster-root formation in three Lupinus species

Abdolzadeh, Ahmad
Wang, Xing
Veneklaas, Erik J.
Lambers, Hans

¹Department of Biology, Faculty of Science, Golsatan University, PO Box 155, Gorgan 49138-15739, Iran
²School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
³School of Plant Nutrition, Faculty of Agriculture, Guangxi University, Nanning, Guangxi 530005, P. R. China

For correspondence. E-mail [email protected]

Annals of Botany 105(3):p 365-374, March 2010.

Background and Aims

In some lupin species, phosphate deficiency induces cluster-root formation, which enhances P uptake by increasing root surface area and, more importantly, the release of root exudates which enhances P availability.

Methods

Three species of Lupinus, L. albus, L. atlanticus and L. micranthus, with inherently different relative growth rates were cultivated under hydroponics in a greenhouse at four phosphate concentrations (1, 10, 50 and 150 µM) to compare the role of internal P in regulating cluster-root formation.

Key Results

The highest growth rate was observed in L. atlanticus, followed by L. albus and L. micranthus. At 1 µM P, cluster-root formation was markedly induced in all three species. The highest P uptake and accumulation was observed in L. micranthus, followed by L. atlanticus and then L. albus. Inhibition of cluster-root formation was severe at 10 µM P in L. atlanticus, but occurred stepwise with increasing P concentration in the root medium in L. albus.

Conclusions

In L. atlanticus and L. albus cluster-root formation was suppressed by P treatments above 10 µM, indicating a P-inducible regulating system for cluster-root formation, as expected. By contrast, production of cluster roots in L. micranthus, in spite of a high internal P concentration, indicated a lower sensitivity to P status, which allowed P-toxicity symptoms to develop.