Table_1_The effects of multiwalled carbon nanotubes and Bacillus subtilis treatments on the salt tolerance of maize seedlings.docx

Nanomaterials, including multiwalled carbon nanotubes (MWCNTs), have been recently applied in agriculture to improve stress resistance, leading to contradictory findings for antioxidant responses and mineral nutrient uptake. A pot experiment involving maize in low-salinity sandy loam soils was conducted with the application of different concentrations (0, 20, 50 mg/L) of MWCNTs and the growth-promoting rhizobacterium Bacillus subtilis (B. subtilis). The dose-dependent effects of MWCNTs were confirmed: 20 mg/L MWCNTs significantly promoted the accumulation of osmolytes in maize, particularly K+ in the leaves and roots, increased the leaf indoleacetic acid content, decreased the leaf abscisic acid content; but the above-mentioned promoting effects decreased significantly in 50 mg/L MWCNTs-treated plants. We observed a synergistic effect of the combined application of MWCNTs and B. subtilis on plant salt tolerance. The increased lipid peroxidation and antioxidant-like proline, peroxidase (POD), and catalase (CAT) activities suggested that MWCNTs induced oxidative stress in maize growing in low-salinity soils. B. subtilis reduced the oxidative stress caused by MWCNTs, as indicated by a lower content of malondialdehyde (MDA). The MWCNTs significantly increased the leaf Na+ content and leaf Na+/K+ ratio; however, when applied in combination with B. subtilis, the leaf Na+/K+ ratio decreased sharply to 69% and 44%, respectively, compared to those of the control (CK) group, the contents of which were partially regulated by abscisic acid and nitrate, according to the results of the structural equation model (SEM). Overall, the increased osmolytes and well-regulated Na+/K+ balance and transport in plants after the combined application of MWCNTs and B. subtilis reveal great potential for their use in combating abiotic stress.

纳米材料，包括多壁碳纳米管（MWCNTs），近期已被应用于农业领域以增强作物抗逆性，然而关于其抗氧化反应和矿物质营养吸收的研究结果却存在矛盾。一项在低盐沙壤土中进行的玉米盆栽实验，研究了不同浓度（0、20、50 mg/L）的MWCNTs以及生长促进菌枯草芽孢杆菌（Bacillus subtilis，简称B. subtilis）对作物生长的影响。实验证实了MWCNTs的剂量依赖性效应：20 mg/L的MWCNTs显著促进了玉米体内渗透调节物质的积累，特别是叶片和根系中的K+，提高了叶片中生长素乙酸的含量，降低了叶片中脱落酸的含量；但在50 mg/L MWCNTs处理的植株中，上述促进效应显著减弱。我们观察到MWCNTs与B. subtilis的联合施用对植物耐盐性具有协同作用。通过提高脂质过氧化和具有抗氧化作用的脯氨酸、过氧化物酶（POD）和过氧化氢酶（CAT）的活性，MWCNTs诱导了低盐土壤中玉米的氧化应激。B. subtilis通过降低丙二醛（MDA）的含量减轻了MWCNTs引起的氧化应激。MWCNTs显著增加了叶片Na+的含量和叶片Na+/K+比值；然而，与B. subtilis联合施用时，叶片Na+/K+比值急剧下降至对照组的69%和44%，其部分原因可归因于脱落酸和硝酸盐的调节作用，如结构方程模型（SEM）的结果所示。总体而言，MWCNTs与B. subtilis联合施用后，植物体内渗透调节物质的增加、Na+/K+平衡和运输的调节，显示出其在对抗非生物胁迫方面的巨大潜力。