Hordeum jubatum L. is a perennial herb with high ornamental value and strong stress tolerance. Nitrogen deposition and cold stress are key environmental factors that affect stability of ecosystems in cold regions of northeast China. These factors significantly affect plant growth and development. Arbuscular mycorrhizal fungi (AMF) are symbiotic soil fungi that can increase plant resistance and growth. However, research on impacts of nitrogen deposition and cold stress on roots of H. jubatum-AM symbionts remains limited. Root biomass (dry and fresh weight), architecture (length, surface area, volume, forks, number of fourth-order roots, and root fractal dimension), and ultrastructure of H. jubatum were assessed, both in the presence and absence of AMF, under conditions of nitrogen deposition and cold stress. Cold stress inhibited all indicators of root architecture and disrupted root ultrastructure, with greater inhibition shown in the N2 (NH4+/NO3- = 1:1) treatment under cold stress, indicating nitrogen deposition increased sensitivity of H. jubatum to cold stress. Inoculation with AMF significantly reduced damage caused by nitrogen deposition and cold stress on H. jubatum roots compared with the non-inoculation treatment. Our results demonstrate different effects of the interaction of nitrogen deposition and cold stress versus single stress (nitrogen deposition or cold stress) on plant root development and provide a scientific basis for the use of mycorrhizal technology to improve resistance and productivity of cold-tolerant plants in cold regions under stress conditions.

The study addresses the critical issue of water scarcity in agriculture, which causes significant losses by disrupting plant -water connections and increasing oxidative damage to biological components. In this study, we evaluated the synergistic potential of pre -isolated and identified exopolysaccharide-producing strains (ZE15 and ZE11) in combination with the drought -alleviating hormone Brassinosteroids (BR) to boost okra development under PEG -6000 -induced drought stress. The experiment was carried out in a controlled environment at the Soil Microbiology and Biotechnology Laboratory. It used a completely randomized design with factorial arrangements and three replications. Individual rhizobacterial strains were evaluated and also used in a consortium (ZE15+ZE11) at two different Brassinosteroids (BR) concentrations (10 -4 M and 10 -8 M). The results showed that the consortium of (ZE15+ZE11) with foliar spray of BR (10 -8 M) greatly increased okra production. Under both control and drought stress conditions, shoot length (37 and 34%), root length (41 and 40%), root surface area (32 and 34%), and root volume (35 and 33%) improved significantly compared to the control group. Furthermore, this treatment demonstrated the most promising results in alleviating drought -induced oxidative damage by improving antioxidant defense mechanisms. Key enzyme activities, such as MDA (30 and 31%), GR (32 and 30%), SOD (36 and 37%), and CAT (31 and 34%), rose significantly under both control and drought stress conditions when compared to the control. To summarize, the use of drought -tolerant bacteria in concert with plant growth hormone provides a synergistic approach to mitigating the negative impacts of drought, resulting in considerable gains in okra growth and antioxidant defenses. This technique shows promise as a way to increase agricultural productivity in arid and semi -arid areas.