چكيده انگليسي :
As greenhouse gases, like carbon dioxide, continue to increase and climate change reveals, it is becoming more evident that there will be consequences, such as reduced water resources in Iran. These conditions will have a significant impact on agricultural production, including the growth of crops like chickpeas. Furthermore, the symbiotic relationship between chickpea plants and Mesorhizobium bacteria is likely to be affected by these changing climate conditions. Therefore, the main objective of this study is to examine the effects of atmospheric carbon dioxide concentration (at levels of 400±50 and 700±50 µmol mol-1), water deficit stress (implemented through irrigation based on 45% and 75% of the maximum allowable depletion of available soil water), and bacterial inoculation (both non-inoculated and inoculated with Mesorhizobium ciceri) on the growth and various morpho-physiological characteristics of four chickpea cultivars (Araz, Samin, Jam, and Karaj 12-60-31). The experimental design follows a factorial approach within a randomized complete block design, with three replications conducted in the open top growth chambers at the Chah-Anari Research Farm of Isfahan University of Technology during the spring of 2022. The results indicated that a high concentration of carbon dioxide had a moderating effect on the impacts of water deficit stress. It led to a reduction in the detrimental effects on stem length, relative leaf water content, increased proline concentration, and enhanced catalase enzyme activity. Moreover, Mesorhizobium inoculation also played a crucial part in mitigating the effects of water deficit stress by increasing the activity of antioxidant enzymes and the number of root nodules. Under these conditions, there was a smaller decrease in plant leaf area and shoot dry weight due to stress, indicating improved stress tolerance and higher efficiency in irrigation water use. However, it is worth noting that Mesorhizobium inoculation under high carbon dioxide concentration resulted in a decrease in root dry weight. Among the cultivars examined, Karaj displayed the highest leaf area, relative leaf water content, shoot dry weight, water use efficiency, and drought stress tolerance index. Additionally, when compared to ambient carbon dioxide concentration, the Karaj variety exhibited the highest leaf area, shoot dry weight, water use efficiency, stress tolerance index, and the least reduction in the number of root nodules under elevated CO2 conditions. Furthermore, under drought stress conditions, the Karaj cultivar demonstrated the greatest increase in chlorophyll a and chlorophyll b content, number of nodes, and water use efficiency compared to the control moisture regime, surpassing other cultivars in performance. Among the plants inoculated with Mesorhizobium, the Araz and Karaj cultivars demonstrated the highest chlorophyll a content and relative leaf water content. The Samin, Jam, and Karaj cultivars exhibited the greatest stem length, while the Samin and Karaj cultivars had the highest number of root nodes. The Karaj cultivar also displayed the highest root dry weight. Overall, under conditions of high carbon dioxide concentration, drought stress, and Mesorhizobium inoculation, the Karaj cultivar exhibited relatively superior performance. According to the findings from correlation and cluster analysis, under control moisture conditions, Samin and Karaj cultivars showed the highest positive correlation with dry weight associated traits, respectively, at ambient and elevated level of CO2. Additionally, when subjected to water shortage stress, Jam at elevated CO2 and Karaj at both carbon dioxide levels displayed a significant correlation with traits related to dry weight. Consequently, it is recommended that future studies pay attention to the Karaj and Jam cultivars as potential subjects for further investigation.
