Nutrient remobilization and C:N:P stoichiometry in response to elevated CO2 and low phosphorus availability in rice cultivars introgressed with and without Pup1

Abstract

The continuously rising atmospheric CO₂ concentration potentially increase plant growth through stimulating C metabolism; however, plant C:N:P stoichiometry in response to elevated CO₂ (eCO₂) under low P stress remains largely unknown. We investigated the combined effect of eCO₂ and low phosphorus on growth, yield, C:N:P stoichiometry, and remobilization in rice cv. Kasalath (aus type), IR64 (a mega rice variety), and IR64-Pup1 (Pup1 QTL introgressed IR64). In response to eCO₂ and low P, the C accumulation increased significantly (particularly at anthesis stage) while N and P concentration decreased leading to higher C:N and C:P ratios in all plant components (leaf, sheath, stem, and grain) than ambient CO₂. The remobilization efficiencies of N and P were also reduced under low P with eCO₂ as compared to control conditions. Among cultivars, the combined effect of eCO₂ and low P was greater in IR64-Pup1 and produced higher biomass and grain yield as compared to IR64. However, IR64-Pup1 exhibited a lower N but higher P concentration than IR64, indicating that the Pup1 QTL improved P uptake but did not influence N uptake. Our study suggests that the P availability along with eCO₂ would alter the C:N:P ratios due to their differential partitioning, thereby affecting growth and yield.

Keywords: C:N:P stoichiometry; Elevated CO(2); Low phosphorus stress; Open top chamber; Pup1 QTL; Remobilization efficiency; Rice.