γ-Fe_(2)O_(3)纳米材料与甲基营养型芽孢杆菌对大豆生长及产量的协同促进机制

Mechanistic study on the synergistic promotion ofγ-Fe_(2)O_(3)nanomaterials and Bacillus methylotrophicus to the growth and yield of soybean(Glycine max)

[目的]探究氧化铁纳米材料(γ-Fe_(2)O_(3)NMs)与甲基营养型芽孢杆菌叶面配施对大豆生长、产量及籽粒品质的影响及其协同作用机制,为γ-Fe_(2)O_(3)NMs在农业生态系统中的应用提供新思路及理论支持。[方法]以大豆为供试作物,纳米材料处理组设置0、1、10、30和50 mg/L 5个浓度,纳米材料与甲基营养型芽孢杆菌复合处理组中包含甲基营养型芽孢杆菌悬液以及对应4个浓度的纳米材料,施用方式为叶面喷施,大豆生长至40天时测定光合作用参数,在成熟期测定植株生物量、植株总糖含量、产量等参数。利用LB平板体外培养实验及分光光度法(OD600)测定γ-Fe_(2)O_(3)NMs对甲基营养型芽孢杆菌生长的影响,利用单颗粒电感耦合等离子质谱仪测定甲基营养型芽孢杆菌对γ-Fe_(2)O_(3)NMs生物可利用性的影响。[结果]γ-Fe_(2)O_(3)NMs促进了大豆光合作用,显著提高了大豆生物量,且30、50 mg/Lγ-Fe_(2)O_(3)NMs明显提高了大豆产量及籽粒碳水化合物含量。与同浓度纳米处理组(30、50 mg/Lγ-Fe_(2)O_(3)NMs)相比,甲基营养型芽孢杆菌与γ-Fe_(2)O_(3)NMs共施用的大豆产量分别增加了31.5%及13.4%。甲基营养型芽孢杆菌施用后相较于对照组显著提高了大豆根尖数,γ-Fe_(2)O_(3)NMs单独处理对大豆根尖数没有显著影响,而γ-Fe_(2)O_(3)NMs与甲基营养型芽孢杆菌共施用处理组中大豆的根尖数明显多于甲基营养型芽孢杆菌单独处理。甲基营养型芽孢杆菌发酵液明显降低了γ-Fe_(2)O_(3)NMs的团聚作用。10、30和50 mg/Lγ-Fe_(2)O_(3)NMs均能够促进甲基营养型芽孢杆菌的生长,且能够使细菌发酵液中吲哚乙酸含量从3.8 mg/L增加至7.6~8.8 mg/L。γ-Fe_(2)O_(3)NMs与甲基营养型芽孢杆菌配合施用,相较于对照组显著提高了大豆养分吸收及籽粒中营养元素(Fe、Mn、S、Mg等)的含量。[结论]γ-Fe_(2)O_(3)NMs对光合作用的促进是其促进大豆生长、提高大豆产量的主要机制。γ-Fe_(2)O_(3)NMs与甲基营养型芽孢杆菌配施后,两者对大豆生长、产量及果实品质呈现协同促进作用。其主要机制包括:1)甲基营养型芽孢杆菌代谢产物能够有效降低γ-Fe_(2)O_(3)NMs的团聚,增加了γ-Fe_(2)O_(3)NMs的生物可利用性;2)γ-Fe_(2)O_(3)NMs显著促进甲基营养型芽孢杆菌生长,提高其代谢产物中吲哚乙酸的含量。

[Objectives]This study aimed to investigate the performance and mechanism of the synergistic effect of applying iron oxide nanomaterials(γ-Fe_(2)O_(3)NMs)and Bacillus methylotrophicus(BM)by foliar method on the growth,yield,and seed quality of soybean.Further,the study provides new insight and basic theoretical support for the application ofγ-Fe_(2)O_(3)NMs in agricultural ecosystems.[Methods]The experimental crop was soybean.For the NMs-treatment group,0,1,10,30,and 50 mg/Lγ-Fe_(2)O_(3)NMs were applied to soybean using the foliar method.BM and a seriesγ-Fe_(2)O_(3)NMs concentrations were co-applied to the leaf of soybean in the coapplicationtreatment group.Photosynthesis parameters of soybean were measured at 40 days of growth,whileplant biomass,total sugar content,and yield were measured at the maturity stage.Luria-Bertani medium in vitroexperiment and OD600 of BM solution were performed to investigate the effect ofγ-Fe_(2)O_(3)NMs on BM's growth.Asingle particle inductively coupled plasma mass spectrometer was used to explore the effect of BM on theγ-Fe_(2)O_(3)NMs bioavailability.[Results]Results indicate that the application ofγ-Fe_(2)O_(3)NMs to soybean by foliar methodimproved its photosynthesis and biomass.Foliar spray ofγ-Fe_(2)O_(3)NMs in 30 and 50 mg/L significantly increasedsoybean yield and carbohydrate content in seed.The co-application of BM andγ-Fe_(2)O_(3)NMs enhanced soybeanyield by 31.5%and 13.4%compared with the single application of 30 and 50 mg/Lγ-Fe_(2)O_(3)NMs.BM treatmentsignificantly increased the number of soybean root tips compared to the control group,whileγ-Fe_(2)O_(3)NMstreatment did not affect the number of soybean root tips.However,the number of soybean root tips with the coapplicationof BM andγ-Fe_(2)O_(3)NMs were(P<0.05)higher than those treated with BM alone.The aggregation ofγ-Fe_(2)O_(3)NMs(P<0.05)reduced in the fermentation broth of BM.10,30,and 50 mg/Lγ-Fe_(2)O_(3)NMs promoted thegrowth of BM,with the attendant increase in indole acetic acid content in the bacterial fermentation broth from3.8 mg/L to 7.6–8.8 mg/L in the presence of 10,30,and 50 mg/Lγ-Fe_(2)O_(3)NMs.The co-application ofγ-Fe_(2)O_(3)NMs and BM enhanced the nutrient uptake of soybean and the elemental nutrient content(e.g.,Fe,Mn,S,Mg)inseed.[Conclusions]γ-Fe_(2)O_(3)NMs enhance the photosynthesis of soybean—the main mechanism forimproving soybean growth and yield.The co-application ofγ-Fe_(2)O_(3)NMs and BM exhibites a synergistic effecton the growth,yield,and seed quality of soybean.The mechanisms identified are that:1)the metabolites of BMeffectively decrease the aggregation ofγ-Fe_(2)O_(3)NMs,thereby promoting its bioavailability;2)γ-Fe_(2)O_(3)NMspromote the growth of BM and the content of indole-3-acetic acid in the metabolites of BM.