Ma Jing, Li Yuhang, Chen Fu, Sun Yan, Zhu Yanfeng, Wang Liping
School of Public Administration, Hohai University, Nanjing, 211100, China.
School of Environmental Science and Spatial Informatics, China University of Mining and Technology, Xuzhou, 221116, China.
Chemosphere. 2023 May;323:138224. doi: 10.1016/j.chemosphere.2023.138224. Epub 2023 Feb 22.
Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil bacteria and are known to induce plant growth promotion and titanium dioxide (TiO)⎯nanoparticles (NPs) used in a range of applications that need increased whiteness, improved corrosion resistance and photocatalytic activity. Keeping in view the stress mitigation potential of TiO⎯NPS and B. mycoides PM35, the existing research work was premeditated to inspect the beneficial role of seed priming with using different levels of TiO⎯NPs i.e., [(0 no TiO⎯NPs), 25 and 50 μg/ml] and soil incubation plant growth promoting rhizobacteria (B. mycoides PM35) i.e., [(0 no B. mycoides PM35), 10 and 20 μL] on biochemical, morphological and physiological characteristics of Barley (Hordeum vulgare L.) plants under different levels of Cd in the soil i.e., [(0 Cd), 50 and 100 mg kg]. Results from the present study showed that the increasing levels of Cd in the soil significantly (P < 0.05) decreased plant growth and biomass, photosynthetic pigments, gas exchange attributes, sugars, and nutritional contents from the roots and shoots of the plants. In contrast, increasing levels of Cd in the soil significantly (P < 0.05) increased oxidative stress indicators in term of malondialdehyde, hydrogen peroxide, and electrolyte leakage, and also increased organic acid exudation patter in the roots of H. vulgare. Although, the activities of enzymatic antioxidants and the response of their gene expressions in the roots and shoots of the plants and non-enzymatic such as phenolic, flavonoid, ascorbic acid, and anthocyanin contents were initially increased with the exposure of 50 mg kg Cd, but decreased by the increasing the Cd concentration 100 mg kg in the soil. The negative impact of Cd toxicity can overcome the application of PGPR (B. mycoides PM35) and TiO⎯NPs, which ultimately increased plant growth and biomass by capturing the reactive oxygen species, and decreased oxidative stress in H. vulgare by decreasing the Cd contents in the roots and shoots of the plants. Our results also showed that the TiO⎯NPs were more sever and showed better results when we compared with PGPR (B. mycoides PM35) under the same treatment of Cd in the soil. Research findings, therefore, suggest that the combined application of PGPR (B. mycoides PM35) and TiO⎯NPs can ameliorate Cd toxicity in H. vulgare, resulting in improved plant growth and composition under metal stress, as depicted by balanced exudation of organic acids.
植物促生根际细菌（PGPR）是天然存在的土壤细菌，已知能促进植物生长，而二氧化钛（TiO）纳米颗粒（NPs）则用于一系列需要提高白度、改善耐腐蚀性和光催化活性的应用中。鉴于TiO NPs和蕈状芽孢杆菌PM35的缓解胁迫潜力，现有的研究工作旨在考察用不同浓度的TiO NPs（即[(0无TiO NPs)、25和50μg/ml]）进行种子引发以及土壤接种植物促生根际细菌（蕈状芽孢杆菌PM35）（即[(0无蕈状芽孢杆菌PM35)、10和20μL]）对不同土壤镉水平（即[(0镉)、50和100mg/kg]）下大麦（Hordeum vulgare L.）植株生化、形态和生理特性的有益作用。本研究结果表明，土壤中镉含量的增加显著（P<0.05）降低了植株的生长、生物量、光合色素、气体交换特性、糖分以及根和地上部的营养成分。相反，土壤中镉含量的增加显著（P<0.05）提高了丙二醛、过氧化氢和电解质渗漏等氧化应激指标，同时也增加了大麦根中有机酸的分泌模式。虽然，植株根和地上部的酶促抗氧化剂活性及其基因表达响应以及酚类、黄酮类、抗坏血酸和花青素等非酶类物质的含量最初在50mg/kg镉处理时有所增加，但随着土壤中镉浓度增加到100mg/kg而降低。镉毒性的负面影响可通过施用PGPR（蕈状芽孢杆菌PM35）和TiO NPs来克服，这最终通过捕获活性氧增加了植株生长和生物量，并通过降低植株根和地上部的镉含量降低了大麦的氧化应激。我们的结果还表明，在土壤镉相同处理条件下，与PGPR（蕈状芽孢杆菌PM35）相比，TiO NPs的效果更显著且更好。因此，研究结果表明，PGPR（蕈状芽孢杆菌PM35）和TiO NPs的联合应用可缓解大麦的镉毒性，从而在金属胁迫下改善植株生长和组成，如有机酸的平衡分泌所示。
