This group has previously reported the role of ascorbic acid (AA) as an antioxidant for survivability and ability to enhancing diazotrophic efficacy in Azotobacter chroococcum Avi2 under hydrogen peroxide (H₂O₂) stress. However, the present study showed the combined application of AA and Avi2 in drought-susceptible (IR64 and Naveen) and drought-tolerant (Ankit and Satyabhama) rice cultivars to determine their photosynthetic efficacy (chlorophyll fluorescence-imaging), antioxidants, and plant growth-promotion (PGP) under moisture deficit stress (MS, −60 kPa). The results indicated that combined application of AA and Avi2 significantly (p < 0.05) increased the total chlorophyll, relative water content, electrolytic leakage, super oxide dismutase, and catalase activities in all rice cultivars as compared to other MS treatments, whereas stress indicators like proline and H₂O₂ contents were proportionally increased under MS and their concentration were normalized under combined application of AA and Avi2. Photochemical quenching, non-photochemical quenching, photosynthetic electron transport rate, and the effective quantum efficiency were found to be increased significantly (p < 0.05) in Avi2 + AA as compared to other MS treatments. Moreover, rice roots harbored significantly (p < 0.05) higher copy number of nifH gene in Avi2 + AA treatment followed by Avi2 compared to flooded control and other MS treatments. Combined application of AA and Avi2 also increased the grain yield significantly (p < 0.05) by 7.09 % and 3.92 % in drought-tolerant (Ankit and Satyabhama, respectively) and 31.70 % and 34.19 % in drought-susceptible (IR64 and Naveen, respectively) rice cultivars compared to MS treatment. Overall, the present study indicated that AA along with Avi2 could be an effective formulation to alleviate MS vis à vis enhances PGP traits in rice.

该小组之前曾报道过抗坏血酸 (AA) 作为抗氧化剂的作用，可在过氧化氢 (H ₂ O ₂ ) 胁迫下提高固氮菌 Avi2中固氮菌的生存能力和能力。然而，本研究表明 AA 和 Avi2 在易旱（IR64 和 Naveen）和耐旱（Ankit 和 Satyabhama）水稻品种中的联合应用，以确定它们的光合功效（叶绿素荧光成像）、抗氧化剂和植物生长- 在水分亏缺压力 (MS, -60 kPa) 下促进 (PGP)。结果表明AA与Avi2联合应用显着（p< 0.05) 与其他 MS 处理相比，所有水稻品种的总叶绿素、相对含水量、电解泄漏、超氧化物歧化酶和过氧化氢酶活性均增加，而脯氨酸和 H ₂ O ₂含量等胁迫指标在 MS 和在 AA 和 Avi2 的联合应用下，它们的浓度被归一化。与其他 MS 处理相比，Avi2 + AA 的光化学猝灭、非光化学猝灭、光合电子传输速率和有效量子效率显着增加（p < 0.05）。此外，水稻根部含有显着 ( p < 0.05) 更高的nifH拷贝数与淹没控制和其他 MS 处理相比，Avi2 + AA 处理中的基因，然后是 Avi2。AA 和 Avi2 的联合施用还显着提高了耐旱（分别为 Ankit 和 Satyabhama）的 7.09 % 和 3.92 % 和耐旱（分别为 IR64 和 Naveen）的 31.70 % 和 34.19 %的谷物产量（p < 0.05） ) 水稻品种与 MS 处理相比。总体而言，本研究表明，AA 和 Avi2 可能是减轻 MS与增强水稻 PGP 性状的有效配方。