Exploitation of localized phosphorus-patches by common bean roots

Phosphorus (P) uptake from patches was investigated in high-P and low-P common bean (Phaseolus vulgar's L.) plants using a split-root system. A P-patch was developed by exposing a small sub-section of the root system to localized P enrichment. A soil-based media was used to provide realistically low, buffered levels of P. In addition, nutrient solution provided zero and 1 mM P to low-P and high-P plants, respectively. Overall, growth of low-P plants was approximately 40% that of high-P plants. Mycorrhizal infection by G. etunicatum had little detectable influence on plant growth. Root length exploring a P-patch was comparable for low-P and high-P plants, yet low-P plants allocated half as much root biomass and P to a P-patch compared to high-P plants. This was achieved by an increase in the investment in fine, terminal roots exploring a P-patch in low-P plants. P uptake per investment of dry weight in the P-patch was over 50% higher for high-P plants compared to low-P plants. The higher P-uptake efficiency in high-P plants was achieved despite the greater production of fine roots in low-P plants.