Article,
Phosphorus supply enhances the response of legumes to elevated CO2 (FACE) in a phosphorus-deficient vertisol
Plant and Soil, 358 (1-2): 91--104 (May 10, 2012)
DOI: 10.1007/s11104-012-1270-z
Abstract
Background & aims
Understanding the mechanism of how phosphorus (P) regulates the response of legumes to elevated CO2 (eCO2) is important for developing P management strategies to cope with increasing atmospheric CO2 concentration. This study aimed to explore this mechanism by investigating interactive effects of CO2 and P supply on root morphology, nodulation and soil P fractions in the rhizosphere.
Methods
A column experiment was conducted under ambient (350 ppm) (aCO2) and eCO2 (550 ppm) in a free air CO2 enrichment (FACE) system. Chickpea and field pea were grown in a P-deficient Vertisol with P addition of 0–16 mg P kg−1.
Results
Increasing P supply increased plant growth and total P uptake with the increase being greater under eCO2 than under aCO2. Elevated CO2 increased root biomass and length, on average, by 16 \% and 14 \%, respectively. Nodule biomass increased by 46 \% in response to eCO2 at 16 mg P kg−1, but was not affected by eCO2 at no P supply. Total P uptake was correlated with root length while N uptake correlated with nodule number and biomass regardless of CO2 level. Elevated CO2 increased the NaOH-extractable organic P by 92 \% when 16 mg P kg−1 was applied.
Conclusion
The increase in P and N uptake and nodule number under eCO2 resulted from the increased biomass production, rather than from changes in specific root-absorbing capability or specific nodule function. Elevated CO2 appears to enhance P immobilization in the rhizosphere.
