C and N metabolism in barley leaves and peduncles modulates responsiveness to changing CO₂
Torralbo, Fernando | Vicente, Rubén | Morcuende, Rosa | González-Murua, Carmen | Aranjuelo, Iker
Balancing of leaf carbohydrates is a key process for maximising crop performance in elevated CO₂ environments. With the aim of testing the role of the carbon sink–source relationship under different CO₂ conditions, we performed two experiments with two barley genotypes (Harrington and RCSL-89) exposed to changing CO₂. In Experiment 1, the genotypes were exposed to 400 and 700 ppm CO₂. Elevated CO₂ induced photosynthetic acclimation in Harrington that was linked with the depletion of Rubisco protein. In contrast, a higher peduncle carbohydrate-storage capacity in RSCL-89 was associated with a better balance of leaf carbohydrates that could help to maximize the photosynthetic capacity under elevated CO₂. In Experiment 2, plants that were grown at 400 ppm or 700 ppm CO₂ for 5 weeks were switched to 700 ppm or 400 ppm CO₂, respectively. Raising CO₂ to 700 ppm increased photosynthetic rates with a reduction in leaf carbohydrate content and an improvement in N assimilation. The increase in nitrate content was associated with up-regulation of genes of protein transcripts of photosynthesis and N assimilation that favoured plant performance under elevated CO₂. Finally, decreasing the CO₂ from 700 ppm to 400 ppm revealed that both stomatal closure and inhibited expression of light-harvesting proteins negatively affected photosynthetic performance and plant growth.
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