Effect of elevated CO2 on phosphorus nutrition of phosphate-deficient Arabidopsis thaliana (L.) Heynh under different nitrogen forms

Phosphorus (P) nutrition is always a key issue regarding plants responses to elevated CO2. Yet it is unclear of how elevated CO2 affects P uptake under different nitrogen (N) forms. This study investigated the influence of elevated CO2 (800 µl l–1) on P uptake and utilization by Arabidopsis grown in pH-buffered phosphate (P)-deficient (0.5 µM) hydroponic culture supplying with 2mM nitrate (NO3 −) or ammonium (NH4 +). After 7 d treatment, elevated CO2 enhanced the biomass production of both NO3 −- and NH4 +-fed plants but decreased the P amount absorbed per weight of roots and the P concentration in the shoots of plants supplied with NH4 +. In comparison, elevated CO2 increased the amount of P absorbed per weight of roots, as well as the P concentration in plants and alleviated P deficiency-induced symptoms of plants supplied with NO3 −. Elevated CO2 also increased the root/shoot ratio, total root surface area, and acid phosphatase activity, and enhanced the expression of genes or transcriptional factors involving in P uptake, allocation and remobilization in P deficient plants. Furthermore, elevated CO2 increased the nitric oxide (NO) level in roots of NO3 −-fed plants but decreased it in NH4 +-fed plants. NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) inhibited plant P acquisition by roots under elevated CO2. Considering all of these findings, this study concluded that a combination of elevated CO2 and NO3 − nutrition can induce a set of plant adaptive strategies to improve P status from P-deficient soluble sources and that NO may be a signalling molecule that controls these processes.