[Effects of high CO₂ concentration, drought, and their interaction on different stay-green wheat seedlings]

In this study, a pot experiment was carried out to examine the effects of high CO₂ concentration, drought and interaction on seedling growth traits, biomass accumulation and physiological characteristics of different stay-green wheat seedlings, with a stay-green wheat variety Yannong 19 and a non stay-green wheat variety Hanxuan 3 as test materials. There were four treatments in the Open Top Chamber with factorial of CO₂ concentration (370 μmol·mol^-1 vs 550 μmol·mol^-1) and drought (45%-55% vs. 75%-85% of field water-holding capacity). Drought significantly inhibited the growth and development of wheat seedlings, while CO₂ concentration significantly increased the number of tillers and promoted the growth and development of wheat seedlings. Under drought condition, high CO₂ concentration increased the number of tillers of Hanxuan 3 and Yannong 19 by 61.0% and 42.3%, respectively. Under both water conditions, high CO₂ concentration significantly increased the biomass of wheat seedlings, and decreased the content of peroxidase and proline in leaves. Under drought condition, high CO₂ concentration showed stronger "fertilizer effect". Furthermore, different varieties had different responses to high CO₂ concentration, with higher sensitivity of Hanxuan 3 to enhancement of CO₂ concentration. Under the scenario of increasing CO₂ concentration, the amount of irrigation water applied to a field can be appropriately reduced for efficient use of water resources. Meanwhile, it is necessary to pay attention to the selection of suitable wheat varieties.