ABA plays an important role in modulating stomatal response to drought and elevated atmospheric CO2 (e [CO2]). This study aimed to investigate the effect of e[CO2] on the response of leaf gas exchange and plant water relations of barley and tomato plants with different endogenous ABA levels to progressive soil drying. Barley and tomato plants were grown in ambient (a[CO2], 400 ppm) and e[CO2] (800 ppm) and subjected to progressive drought stress. Wild type (WT) genotypes (Steptoe barley and AC tomato) and their ABA-deficient mutants (Az34 barley and flacca) were examined. e[CO2] sensitized the photosynthetic decline with soil drying. Soil-drying induced stomatal closure was affected by [CO2] in WT genotypes, where e[CO2] sensitized stomatal closure in barley but retarded it in tomato, whereas such effects were absent in mutants. Compared to a[CO2], e[CO2] maintained leaf water potential and improved turgor pressure except in the flacca mutant. For the WT genotypes, the stomata became less sensitive to an increase in leaf ABA concentration ([ABA]leaf) under e[CO2] than a[CO2]; while for both mutants, the stomata was predominately controlled by leaf turgor and not an increase in [ABA]leaf during soil drying. Endogenous ABA level played an important role in modulating the effect of e[CO2] on stomatal response to soil drying. These findings improve our understanding of the mechanisms of stomatal control in monocot and dicot species responding to a future drier and CO2-enriched environment.

中文翻译：

---

大气 CO2 升高对不同内源 ABA 水平的大麦和番茄植物叶片气体交换对渐进性干旱响应的影响

ABA 在调节气孔对干旱和大气 CO2 (e [CO2]) 升高的响应方面发挥着重要作用。本研究旨在研究 e[CO2] 对不同内源 ABA 水平的大麦和番茄植物叶片气体交换响应和植物水分关系对渐进式土壤干燥的影响。大麦和番茄植物在环境 (a[CO2], 400 ppm) 和 e[CO2] (800 ppm) 中生长，并经受渐进式干旱胁迫。检查了野生型 (WT) 基因型（Steptoe 大麦和 AC 番茄）及其缺乏 ABA 的突变体（Az34 大麦和 flacca）。e[CO2] 使土壤干燥导致光合下降敏感。土壤干燥诱导的气孔关闭受 WT 基因型中 [CO2] 的影响，其中 e[CO2] 使大麦中的气孔关闭敏感，但在番茄中延迟了气孔关闭，而突变体中不存在这种影响。与a[CO2]相比，除 flacca 突变体外，e[CO2] 保持了叶水势并提高了膨压。对于 WT 基因型，在 e[CO2] 下，气孔对叶 ABA 浓度（[ABA]leaf）的增加比 a[CO2] 更不敏感；而对于这两个突变体，气孔主要受叶片膨压控制，而不是在土壤干燥过程中 [ABA] 叶片的增加。内源ABA水平在调节e[CO2]对土壤干燥气孔响应的影响中起重要作用。这些发现提高了我们对单子叶植物和双子叶植物物种对未来干燥和富含二氧化碳的环境的气孔控制机制的理解。在 e[CO2] 下，气孔对叶 ABA 浓度（[ABA]leaf）的增加比 a[CO2] 更不敏感；而对于这两个突变体，气孔主要受叶片膨压控制，而不是在土壤干燥过程中 [ABA] 叶片的增加。内源ABA水平在调节e[CO2]对土壤干燥气孔响应的影响中起重要作用。这些发现提高了我们对单子叶植物和双子叶植物物种对未来干燥和富含二氧化碳的环境的气孔控制机制的理解。在e[CO2]下，气孔对叶ABA浓度（[ABA]leaf）的增加比a[CO2]更不敏感；而对于这两个突变体，气孔主要受叶片膨压控制，而不是在土壤干燥过程中 [ABA] 叶片的增加。内源ABA水平在调节e[CO2]对土壤干燥气孔响应的影响中起重要作用。这些发现提高了我们对单子叶植物和双子叶植物物种对未来干燥和富含二氧化碳的环境的气孔控制机制的理解。