Effects of phosphorus supply on growth, phosphate concentration and cluster-root formation in three Lupinus species.
OBJECTIVE
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 microm) to compare the role of internal P in regulating cluster-root formation.


RESULTS
The highest growth rate was observed in L. atlanticus, followed by L. albus and L. micranthus. At 1 microm 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 microm 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 microm, 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.
Abdolzadeh
Ahmad
A
Department of Biology, Faculty of Science, Golsatan University, PO Box 155, Gorgan 49138-15739, Iran. ah_ab99@yahoo.com
Wang
Xing
X
Veneklaas
Erik J
EJ
Lambers
Hans
H
D031297:Lupinus / Q000254:growth & development* / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D013045:Species Specificity
D010758:Phosphorus