Cluster Root Formation by Lupinus Albus is Modified by Stratified Application of Phosphorus in a Split-Root System

ABSTRACT

Cluster root formation by white lupin (Lupinus albus L. cv. Kiev Mutant) in response to stratified application of hydroxyapatite was examined in a split-root system. The system consisted of two vertical compartments, each divided horizontally into five 60-mm layers. Hydroxyapatite was applied to different layers at 150 mg phosphorus(P) kg⁻¹ soil. The proportion of dry biomass of cluster roots in the whole root system was significantly reduced when P concentration was high in shoots due to P application, suggesting that cluster root formation was regulated by the shoot P status. However, the cluster root percentage increased in the soil layer supplemented with P, and decreased in other layers, especially when P was applied in a deep layer. The formation of cluster roots is regulated by internal plant P status, but is also greatly affected by localized P supply. Heterogeneous P supply can modify the distribution of cluster roots.

Keywords:

• cluster root
• phosphorus
• split-root system
• stratified application
• white lupin

ACKNOWLEDGMENTS

This study was supported by the National Natural Science Foundation of China (No. 30671238; 30471033), the Ministry of Science and Technology of China (No. 2006BAD25B02), Program for Changjiang Scholar and Innovation Research Team (No. IRT0511) and New Century Excellent Talents in University of China, and Australian Research Council.