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The responses of leaf gas exchange of wheat (Triticum aestivum L.) to elevated atmospheric CO 2 concentration (eCO 2) were ofteninvestigated within a single generation, while the long-term acclimation of photosynthesis to growth in eCO 2 over multiple gen-erations has not been systematically studied. Here, five wheat cultivars were grown under either ambient (aCO 2, 400 ppm) orelevated (eCO 2, 800 ppm) CO 2 concentration for three consecutive generations (G1 to G3) with two N-fertilisation levels (1N–1 gN pot−1 and 2N–2 g N pot−1) in climate-controlled greenhouses. Leaf gas exchange was determined in each generation of plantsunder different treatments. It was found that at both N levels, eCO 2 stimulated photosynthetic rate while reducing stomatalconductance, transpiration rate and leaf N concentration, resulting in an enhanced water use efficiency and photosynthetic Nuse efficiency. The N level modulated the intergenerational responses of photosynthetic capacity to eCO 2; under low N supply,the maximum carboxylation rate (Vcmax), the maximum electron transport rate (Jmax) and the rate of triose phosphate utilisation(TPU) were significantly downregulated by eCO 2 from the first to the second generation, but recovered in the third generation;whereas at high N levels, photosynthetic acclimation was diminished with the progress of generations, with Vcmax , Jmax andTPU increased under eCO 2 in the third generation. These results suggest that intergenerational adaptation could alleviate theeCO 2-induced reduction of the photosynthetic capacity, but plants with different N status responded differently to adapt to thelong-term exposure to eCO 2. Among the five cultivars, 325Jimai showed a better photosynthetic performance under eCO 2over the three generations, while 02-1Shiluan appeared to be more inhibited by CO 2 elevation in the long term conditions. Thesefindings provide new insights for breeding strategies in the future CO 2 -enriched environments.
Wang et al. (Mon,) studied this question.