Multigenerational Effects of Elevated CO2 and N Supply on Leaf Gas Exchange Traits in Wheat Plants

ABSTRACT The responses of leaf gas exchange of wheat ( Triticum aestivum L.) to elevated atmospheric CO 2 concentration ( e [CO 2 ]) were often investigated within a single generation, while the long‐term acclimation of photosynthesis to growth in e [CO 2 ] over multiple generations has not been systematically studied. Here, five wheat cultivars were grown under either ambient ( a [CO 2 ], 400 ppm) or elevated ( e [CO 2 ], 800 ppm) CO 2 concentration for three consecutive generations (G1 to G3) with two N‐fertilisation levels (1N–1 g N pot −1 and 2N–2 g N pot −1 ) in climate‐controlled greenhouses. Leaf gas exchange was determined in each generation of plants under different treatments. It was found that at both N levels, e [CO 2 ] stimulated photosynthetic rate while reducing stomatal conductance, transpiration rate and leaf N concentration, resulting in an enhanced water use efficiency and photosynthetic N use efficiency. The N level modulated the intergenerational responses of photosynthetic capacity to e [CO 2 ]; under low N supply, the maximum carboxylation rate ( V cmax ), the maximum electron transport rate ( J max ) and the rate of triose phosphate utilisation (TPU) were significantly downregulated by e [CO 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 V cmax , J max and TPU increased under e [CO 2 ] in the third generation. These results suggest that intergenerational adaptation could alleviate the e [CO 2 ]‐induced reduction of the photosynthetic capacity, but plants with different N status responded differently to adapt to the long‐term exposure to e [CO 2 ]. Among the five cultivars, 325Jimai showed a better photosynthetic performance under e [CO 2 ] over the three generations, while 02‐1Shiluan appeared to be more inhibited by CO 2 elevation in the long term conditions. These findings provide new insights for breeding strategies in the future CO 2 ‐enriched environments.