兰州大学机构库 >生态学院
丛枝菌根真菌与纳米零价铁耦合对旱地玉米根际过程和产量形成的影响及机制
Alternative TitleEffects of AM fungi coupled with nanoscale zero valent iron on rhizosphere process and yield formation and the mechanisms in dryland maize
杨育苗
Subtype博士
Thesis Advisor熊友才
2023-09-04
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline生态学
Keyword纳米零价铁 nanoscale zero valent iron (nZVI) 丛枝菌根真菌 arbuscular mycorrhizal fungi (AMF) 菌根共生体 mycorrhizal symbiont 浓度依赖效应 rhizosphere process 产量形 成 concentration dependence 根际过程 yield formation 土壤碳固存 soil carbon sequestration 旱地玉米 dryland maize
Abstract

纳米材料因其较大的比表面积和高生物活性,在纳米农业中有巨大应用潜力,比如纳米微肥研发与应用。丛枝菌根(arbuscular mycorrhizal,AM)真菌作为陆地生态系统中最普遍的土壤功能微生物,被广泛证实可促进植物生长并提高植物抗逆性。纳米零价铁(nanoscale zero valent iron,nZVI)能否作为高效纳米微肥被纳入菌根共生系统中、继而影响作物的生长与菌根的发育?与AMF菌根共生体的互作机制是什么?有没有潜在风险?这些问题是农业生态学中的基础科学问题。针对旱地作物与土壤互作系统来说,不同剂量的nZVI添加对菌根共生体结构、功能和根际微生物群落的影响尚不明确,菌根共生体如何调控nZVI对作物生长的正/负效应?nZVI对作物的影响是其纳米结构特性导致还是其元素养分特性所导致?以及nZVI与AM真菌耦合对旱地农田土壤碳固存及作物产量形成机制等问题均有待进一步研究。

本研究以旱地春玉米(Zea mays L.)为试验材料,于2019-2022年采用盆栽试验和田间试验相结合的模式,外源接种AM真菌(Funneliformis mosseae)并拌种施加纳米零价铁(nZVI)颗粒,系统观测了玉米生理生化指标、叶片光合参数、菌根定殖参数、植株铁元素的分布与转运、抗氧化系统活性、玉米产量构成因子、土壤质量和碳固存潜力,并分析了土壤真菌群落演变以及菌根共生体的微观结构特征。通过数理统计分析,揭示AM真菌与nZVI耦合对旱地玉米发育和产量形成的影响及机制,主要结果如下:

1)nZVI的最适拌种浓度筛选及其与AM真菌耦合对玉米发育和根际过程的影响

(1)梯度拌种试验结果表明随着浓度的增加,nZVI对玉米植株的促生作用先增强后减弱,1.5 g kg-1为nZVI对玉米种的最适拌种浓度,此浓度下玉米植株收获期形态指标分别显著增加了21.66%(株高,p<0.01)、10.71%(叶面积,p<0.01)、15.27%(地上生物量,p<0.05)和24.08%(地下生物量,p<0.05)。

(2)nZVI对玉米的发育有着显著的浓度依赖效应,表现为低浓度促生而高浓度抑制。适量的nZVI(1.5 g kg-1)拌种使玉米叶片Pn和Cond分别增加70.77%(p<0.05)和47.47%(p<0.05),显著提高了Pnmax(p<0.05)并降低了LCP(p<0.001),这有助于玉米光合潜力的提高及同化产物的积累,导致玉米生物量上涨了15.83%(p<0.01)。此外,适量的nZVI添加还可提高玉米叶片Chl (a+b)含量(p<0.01)、Rubisco及其活化酶活性(p<0.01)以及Fecy(p<0.01)和NADP(p<0.05)的光还原性,继而强化了nZVI对玉米光合过程的积极影响。

(3)SEM/EDX图像表明,高剂量的nZVI(2 g kg-1)添加使得大量纳米铁颗粒于玉米根表面团聚附着,形成晶状难溶性铁(Fe3+)氧化层并堵塞根表孔隙,阻碍玉米根系对水分和养分的吸收,致使玉米叶片LWC和WUEplant分别减少4.96%(p<0.05)和19.54%(p<0.05),WSD增加3.91%(p<0.05),并最终导致玉米生物量下降了6.83%(p<0.01)。高剂量的nZVI还会增加植株活性氧水平,进而刺激细胞渗透调节机制、加重膜脂过氧化损伤并提高抗氧化系统酶活性,使叶片中Pro和MDA含量分别增加了43.42%和43.08%(p<0.05),SOD和POD活性分别提高了37.51%和32.40%(p<0.05)。

(4)nZVI对AM真菌的根际定殖同样影响显著。适量nZVI(1.5 g kg-1)拌种显著增加了RCR(p<0.05)、EHL(p<0.01)和GRSP(p<0.05),提高了土壤真菌群落的丰富度(Ace Index,p<0.01)并降低了群落的多样性(Shannon Index,p<0.05),此外还使Glomeromycota门Funneliformis属的相对丰度大幅增加,表明试验所接种的Funneliformis mosseae在玉米根际成功定殖并发展为优势菌种。相反,高剂量nZVI(2 g kg-1)则使RCR和EHL分别显著下降13.90%和13.13%,GRSP显著降低11.15%-13.98%。SEM图像同样证实了高剂量nZVI对菌根结构的负面影响。高剂量nZVI的添加可使孢子表面出现不规则褶皱和萎缩,菌丝明显变形失活,最终导致共生体功能的丧失。

(5)AM真菌的接种可增强低剂量nZVI对玉米的促生效应并缓解高剂量nZVI的胁迫作用,对nZVI表现出双向稳性调控效应。一方面,适量nZVI通过提高植株光合产物的积累,可向AM真菌提供更多的碳源和定殖载体,促进菌根的定殖与发育。同时,发育良好的菌根共生体又可增强宿主植物对水分和养分的吸收,进而形成正向的反馈循环。另一方面,高剂量nZVI条件下AM真菌可通过其根外菌丝体将过量的纳米铁颗粒拦蓄固持,使玉米铁转运率和茎部铁浓度分别下降8.77%(p<0.05)和6.26%(p<0.05),将玉米地上部分的铁浓度稳定在300 mg kg-1左右。

2)nZVI与FeSO4对AM真菌-玉米共生体的差异性影响

(6)nZVI处理对玉米的发育及AM真菌的定殖具有显著的正/负效应,而FeSO4处理则对上述过程影响不显著。低剂量纳米铁(FN-L)显著提高了玉米叶片的Pn(19.40%,p<0.01)、Cond(53.45%,p<0.05)和Chl (a+b)(12.31%,p<0.05),导致植株生物量增加19.84%(p<0.05),进而为菌根定殖提供了充足的碳源及载体。同时,FN-L还显著增加了RCR(p<0.05)、EHL(p<0.05)和GRSP(p<0.05),表明FN-L成功介导了植物光合及菌根共生过程中光合碳与水分/养分间的物质交换,驱动了两系统间的正相互作用。然而相同剂量的FeSO4对玉米光合及共生过程的影响均不显著,未能有效介导植株地上、地下两系统间的物质供求循环,表明本研究中nZVI对AM真菌-玉米共生体的促生作用主要源于其纳米结构特性而非其元素养分特性。

(7)相较于高剂量铁盐(FS-H)处理,高剂量纳米铁(FN-H)显著降低了玉米叶片Cond(p<0.05)、WUE(p<0.05)和Chl (a+b)(p<0.05),致使玉米光合产物积累下降了13.89%(p<0.05)。此外,FN-H处理显著降低RCR(p<0.05)、EHL(p<0.05)和GRSP(p<0.05),而FS-H对上述定殖参数影响不显著。同样,MIR-Shoot在FN-H条件下小于零而在FS-H大于零,表明菌根共生体对高剂量纳米铁的原位固持作用大于铁盐,这也证实了高剂量纳米铁具有远高于铁盐的环境风险。

3)nZVI与AM真菌耦合对旱地农田土壤质量及玉米产量形成的影响

(8)相较于对照,AMF+N1处理显著提高了土壤大颗粒团聚体(> 0.25 mm)比例(35.18%-41.16%)、MWD(26.91%-32.23%)和GMD(30.61%-35.38%)并降低了SBD(4.69%-5.08%),表明AMF+N1模式有助于促进土壤团聚化进程并可提高土壤稳定性,改善土壤结构,这一趋势在接种后的第二个生长季(2020年)更为显著。

(9)AMF+nZVI模式有助于旱地农田土壤的碳固存。首先,AM真菌接种条件下适量nZVI添加可提高叶片的Pn(36.74%-47.02%,p<0.05)和Cond(40.74%-47.14%,p<0.05),有助于玉米植株以生物量积累的形式吸收固定大气中的CO2。其次,适量nZVI可促进根际菌丝体的发育(20.83%-26.67%,p<0.05)及球囊霉素的分泌(8.65%-16.96%,EE-GRSP;7.69%-21.74%,T-GRSP),二者不仅本身作为土壤有机碳库的重要组成部分,而且可以通过“粘绳袋(sticky-string-bag)”效应促进土壤团聚化以减少土壤碳质化合物的分解,导致土壤总有机碳含量增加(6.16%-7.80%,p<0.05),进而增强了旱地农田土壤的碳汇属性。

(10)本研究中AMF+nZVI模式虽对玉米产量有着显著的促进作用,但地膜覆盖仍是目前影响黄土高原旱地玉米产量形成最主要的因素。相较于对照,覆膜和AMF+nZVI模式在2019年对玉米籽粒产量分别提高了17.8%和5.6%,2020年则分别提高了18.6%和9.4%。短期而言,AMF+nZVI模式的单独应用已展现出一定的地膜替代潜力,且随着接种年限的增加,AMF+nZVI模式对玉米产量的提升更显著。此外,AMF+nZVI模式也可与现有的地膜覆盖系统结合应用,以实现经济效益的最大化。长远而言,AMF+nZVI模式相较于地膜覆盖系统对土壤的养分循环、结构改善及微生物群落发育更为友好,有助于旱地农业的可持续性发展。

综上所述,适量nZVI可作为微量元素肥料可有效的强化作物铁营养,并通过介导玉米光合系统与菌根共生系统间物质的交换形成正反馈循环,促进旱地玉米产量形成及菌根共生体的发育。AM真菌的接种通过菌丝体的原位固持效应对nZVI表现出双向稳定性,即低浓度nZVI条件下AM真菌可进一步增强nZVI对玉米的促生作用,而在高浓度nZVI条件下显著缓解nZVI对玉米的负面影响,进而拓展nZVI对玉米促生发育的浓度阈值。此外,nZVI与AM真菌耦合可有效促进旱地农田土壤团聚化进程和有机碳的封存,并表现出显著的产量提升潜力。以上结论为全球气候变化背景下铁基纳米材料在旱地农业生态系统中安全高效应用及其风险防控提供了新的见解。

Other Abstract

Nanomaterials hold tremendous potential in nano-agriculture due to their larger surface area and high biological activity, such as nano-biofertilizers. Arbuscular mycorrhizal (AM) fungi, as the most widespread soil functional microorganisms in terrestrial ecosystems, have been widely confirmed to promote plant growth and enhance plant stress resistance. Can nanoscale zero valent iron (nZVI) be incorporated into mycorrhizal symbiotic systems as an efficient nano-biofertilizer, subsequently influencing crop growth and mycorrhizal development? What are the interaction mechanisms between nZVI and AMF mycorrhizal symbiosis? Are there any potential risks associated with this? These questions represent fundamental scientific inquiries in agricultural ecology. For rainfed crops and soil interaction systems, the effects of different doses of nZVI on mycorrhizal symbiotic structures, functions, and rhizospheric microbial communities remain unclear. How does mycorrhizal symbiosis regulate the positive/negative effects of nZVI on crop growth? Are the effects of nZVI on crops attributed to its nanostructural characteristics or its elemental nutrient properties? Furthermore, the mechanisms of nZVI-AM fungi coupling on soil carbon sequestration in rainfed farmland and crop yield formation require further investigation.

In this study, spring maize (Zea mays L.) was used as the experimental material, using a combination of pot and field experiments (2019-2020) to systematically observe physiological and biochemical indicators, photosynthetic parameters, mycorrhizal colonization parameters, plant iron distribution and transport, antioxidant enzyme activities, maize yield components, soil quality and carbon sequestration potential, and microstructure characteristics of mycorrhizal symbionts. In order to explore the effects and mechanisms of coupling AM fungi with nZVI on the development and yield formation of dryland maize. The main conclusions are as follows:

1. Determination of the optimal seed-dressing concentration of nZVI and its effect on maize development and rhizosphere process coupled with AM fungi.

(1) The results of gradient seed dressing experiment showed that with the increase of nZVI concentration, the growth promotion effect of nZVI on maize plants first increased and then decreased, and 1.5 g kg-1 was the optimal seed dressing concentration for nZVI on maize. 1.5 g kg-1 of nZVI significantly increased the morphological indicators of maize plants at harvesting stage by 21.66% (plant height, p<0.01), 10.71% (leaf area, p<0.01), 15.27% (aboveground biomass, p<0.05), and 24.08% (underground biomass, p<0.05), respectively.

(2) nZVI had a significant concentration dependent effect on maize development, showing that low concentration of nZVI promoted growth while high concentration of nZVI inhibited growth. Appropriate dose of nZVI (1.5 g kg-1) significantly increased Pn and Cond in maize leaves by 70.77% (p<0.05) and 47.47% (p<0.05), respectively, and increased Pnmax (p<0.05) but decreased LCP (p<0.001). This contributed to the improvement of maize photosynthetic potential and the accumulation of assimilation products, resulting in a 15.83% increase in maize biomass (p<0.01). In addition, appropriate nZVI could also increase the Chl (a+b) content (p<0.01), Rubisco and its activating enzyme activity (p<0.01), as well as the photoreduction of Fecy (p<0.01) and NADP (p<0.05) in maize leaves, thereby strengthening the positive effect of nZVI on the photosynthetic process of maize.

(3) SEM/EDX images showed that high dose of nZVI (2 g kg-1) caused a large number of nano iron particles to aggregate and adhere to the surface of maize roots, forming a crystalline insoluble iron oxide (Fe3+) layer and blocking root surface apertures, hindering the absorption of water and nutrients by maize roots. This phenomenon caused LWC and WUE to decrease by 4.96% (p<0.05) and 19.54% (p<0.05), WSD increased by 3.91% (p<0.05), and eventually led to a decrease of maize biomass by 6.83% (p<0.01). High dose of nZVI could also increase the level of reactive oxygen species in plants, thereby stimulating cell osmotic regulation mechanisms, aggravating membrane lipid peroxidation damage, and increasing antioxidant system enzyme activity. This results in an increase of 43.42% (p<0.05) and 43.08% (p<0.05) in Pro and MDA content, as well as an increase of 37.51% (p<0.05) and 32.40% (p<0.05) in SOD and POD activities, respectively.

(4) nZVI also had significant effects on the colonization of AM fungi. Appropriate dose of nZVI (1.5 g kg-1) significantly increased RCR (p<0.05), EHL (p<0.01), and GRSP (p<0.05). The richness of soil fungal community was increased (Ace index, p<0.01) while decreased community diversity (Shannon index, p<0.05). Moreover, the relative abundance of the Funneliformis genus in the Glomeromycota phylum increased significantly, indicating that the Funneliformis mosseae inoculated in this experiment had successfully colonized and developed into a dominant strain in the maize rhizosphere. On the contrary, high dose of nZVI (2 g kg-1) significantly reduced RCR and EHL by 13.90% and 13.13%, respectively, and GRSP by 11.15%-13.98%. SEM images also confirmed the negative effect of high dose nZVI on mycorrhizal structure. High dose of nZVI could cause irregular folding and atrophy of spores, obvious deformation and inactivation of hyphae, and ultimately leading to the loss of symbiotic function.

(5) AM fungi inoculation could enhance the promoting effect of low dose nZVI on maize and alleviate the stress effect of high dose nZVI, showing bidirectional stability to nZVI. On the one hand, an appropriate amount of nZVI could provide more carbon sources and colonization carriers to AM fungi by increasing the accumulation of plant photosynthetic products, promoting the colonization and development of mycorrhiza. Meanwhile, well-developed mycorrhizal symbionts could enhance the host plant's absorption of water and nutrients, thereby forming a positive feedback loop. On the other hand, under the condition of high dose of nZVI, AM fungi could accumulate excess nanoiron particles through extramatrical hyphae, resulting in a decrease of 8.77% (p<0.05) in translocation efficiency and 6.26% (p<0.05) in shoot iron content. Stabilized the shoot iron content of maize at around 300 mg kg-1.

2. Different effects of nZVI and FeSO4 on AM fungi-maize symbionts.

(6) nZVI treatments had significant positive/negative effects on the development of maize and the colonization of AM fungi, while FeSO4 treatments had no significant effect on the above processes. Low dose of nZVI (FN-L) significantly increased the Pn (19.40%, p<0.01), Cond (53.45%, p<0.05) and Chl (a+b) (12.31%, p<0.05), which resulted in a 19.84% increase in maize biomass (p<0.05), and provided sufficient carbon sources and carriers for mycorrhizal colonization. Simultaneously, FN-L also significantly increased RCR (p<0.05), EHL (p<0.05) and GRSP (p<0.05), indicating that FN-L successfully mediated the material exchange between photosynthetic carbon and water/nutrients during plant photosynthesis and mycorrhizal symbiosis, driving the positive interaction between the two systems. However, FeSO4 with the same dose had no significant influence on maize photosynthesis and symbiosis, and it failed to effectively mediate the material supply and demand cycle between the aboveground and underground systems of the plant, indicating that the growth promoting effect of nZVI on AM fungi-maize symbionts in this study was mainly due to its nanostructure properties rather than its element nutrient properties.

(7) Compared with high dose of FeSO4 (FS-H), high dose of nZVI (FN-H) significantly reduced the Cond (p<0.05), WUE (p<0.05) and Chl (a+b) (p<0.05), resulting in a 13.89% (p<0.05) decrease in the accumulation of photosynthetic products in maize. Furthermore, FN-H significantly reduced RCR (p<0.05), EHL (p<0.05) and GRSP (p<0.05), while FS-H had no significant effect on the above colonization parameters. Similarly, MIR-Shoot was less than zero under FN-H conditions but greater than zero under FS-H conditions, indicating that mycorrhizal symbionts had greater in situ fixation effects on FN-H than FS-H, which also confirmed that high dose of nZVI had a higher environmental risk than FeSO4.

3. Effects of coupling nZVI and AM fungi on soil quality and maize yield formation in arid farmland.

(8) Compared with the control, AMF+N1 treatment significantly increased the proportion of soil macroaggregates (>0.25 mm) (35.18%-41.16%), MWD (26.91%-32.23%) and GMD (30.61%-35.38%), but reduced SBD (4.69%-5.08%), indicating that AMF+N1 could promote soil agglomeration process and improve soil stability. This trend was more significant in the second growth season (2020) after AMF inoculation.

(9) The AMF+nZVI pattern contributed to carbon sequestration in arid farmland soils. Firstly, appropriate dose of nZVI under AMF inoculation could increase Pn (36.74%-47.02%, p<0.05) and Cond (40.74%-47.14%, p<0.05) of leaves, which helped maize plants absorb and fix CO2 in the atmosphere through biomass accumulation. Secondly, appropriate dose of nZVI could promote the development of rhizosphere mycelium (20.83%-26.67%, p<0.05) and the secretion of GRSP (8.65%-16.96, EE-GRSP; 7.69%-21.74%, T-GRSP), which were not only important components of soil organic carbon pool, but also promoted soil aggregation through "sticky-string-bag" effect to reduce the decomposition of soil carbon compounds. It led to the increase of soil total organic carbon (6.16%-7.80%, p<0.05), which further enhanced the carbon sink property of arid farmland soil.

(10) In this study, although the AMF+nZVI pattern had a significant promoting effect on maize yield, mulching was still the main factor affecting the formation of maize yield in the dry land of the Loess Plateau. Compared with the control, mulching and AMF+nZVI pattern increased maize grain yield by 17.8% and 5.6% in 2019 and 18.6% and 9.4% in 2020, respectively. In the short term, the individual application of AMF+nZVI had shown certain potential for replacing plastic film, and with the increase of inoculation years, the AMF+nZVI pattern had more significant improvements in maize yield. In addition, the AMF+nZVI pattern could also be combined with the mulching systems to maximize economic benefits. In the long term, the AMF+nZVI pattern was more friendly to soil nutrient cycling, structural improvement and microbial community development than the mulching treatment, which contributed to the sustainable development of arid agriculture.

In conclusion, appropriate dose of nZVI could be used as a micronutrient fertilizer to effectively strengthen crop iron nutrition, and formed a positive feedback loop by mediating the exchange of substances between maize photosynthetic system and mycorrhizal symbiosis system, so as to promote the yield formation of maize and the development of mycorrhizal symbionts. The inoculation of AMF showed bidirectional stability on nZVI through the in situ retention effect of mycelium, that was, AMF could further enhance the growth promoting effect of nZVI on maize under low dose of nZVI, and significantly alleviated the negative effect of nZVI on maize under high dose of nZVI, thereby expanding the concentration threshold of nZVI on maize development. Moreover, the coupling of nZVI and AMF could effectively promote the process of soil aggregation and the storage of organic carbon in arid farmland, and demonstrate excellent yield enhancement potential. The above conclusions provided new insights into the safe and efficient application of iron based nanomaterials in arid agricultural ecosystems and their risk prevention under the background of global climate change.

MOST Discipline Catalogue理学 - 生态学
URL查看原文
Language中文
Other Code262010_120180905011
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/538351
Collection生态学院
Affiliation
兰州大学生态学院
Recommended Citation
GB/T 7714
杨育苗. 丛枝菌根真菌与纳米零价铁耦合对旱地玉米根际过程和产量形成的影响及机制[D]. 兰州. 兰州大学,2023.
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