不同磷水平下丛枝菌根真菌对纳米氧化锌生物效应的影响

纳米ZnO颗粒是应用最为广泛金属型纳米颗粒(nanoparticles,NPs)之一,对作物和土壤微生物的影响值得关注.丛枝菌根(arbuscular mycorrhizal,AM)是自然界中普遍存在的植物-真菌共生体,对各种环境胁迫具有一定的抵御能力,但菌根效应受土壤和植物磷含量的影响.分别设置0、20、50、100 mg·kg~(-1)这4个磷水平,在接种或不接种AM真菌Funneliformis mosseae、添加或不添加纳米ZnO(500 mg·kg~(-1))条件下在温室中利用玉米进行土壤盆栽试验.结果表明,纳米ZnO没有显著影响玉米生长,但不利于菌根侵染和磷素吸收,并引起锌在植物体内的积累.纳米ZnO和高磷降低玉米菌根侵染,但AM真菌在所有磷水平下均显著促进植物生长.施磷和接菌均可使土壤p H升高、降低纳米ZnO源锌的生物有效性,从而降低锌向玉米地上部分的转运和积累,体现出一定保护作用.接菌在多数情况下显示出积极的菌根效应,尤其在低磷、添加纳米ZnO条件下更为显著.结果首次表明,AM真菌、磷肥均有助于减轻纳米ZnO引起的土壤污染及其所产生的生态和健康风险.

Biological Effects of ZnO Nanoparticles as Influenced by Arbuscular Mycorrhizal Inoculation and Phosphorus Fertilization

ZnO nanoparticles (NPs) are widely used in many applications, such as plastics, ceramics, glass, cement, rubber, lubricants, paints, pigments, batteries, fire retardants, catalysts, and anti-microbial agents. They directly or indirectly enter aquatic and terrestrial environments through application, accidental release, contaminated soil/sediments, or atmospheric fallouts. When present in excess, ZnO NPs can induce phytotoxicity and reduce plant growth and yields. ZnO NPs can also cause Zn accumulation in edible parts of food crops, and then subsequently enter human bodies and pose a significant health risk. Arbuscular mycorrhizae are ubiquitous symbiotic associations in nature formed between arbuscular mycorrhizal (AM) fungi and most higher plants in terrestrial ecosystems. In addition to their well-known contribution to plant nutrient acquisition and growth, AM fungi can improve plant tolerance to various environmental stresses, but mycorrhizal effects vary with environmental conditions such as phosphorus status in both soil and plants. AM fungi have been shown to alleviate the negative effects of ZnO NPs and zinc accumulation in plants, however, the role of phosphorus fertilization has been neglected. A greenhouse pot culture experiment was conducted using maize as the test plant inoculated with or without AM fungus Funneliformis mosseae. Four levels of phosphorus (0, 20, 50 or 100 mg·kg^-1) and two levels of ZnO NPs (0 or 500 mg·kg^-1) were applied to pots. Shoots and roots were harvested separately after two months of growth. Mycorrhizal infection, plant biomass, P and Zn concentrations and uptake in plants, and soil DTPA-extractable zinc and pH were determined. The results showed that ZnO NPs did not significantly affect the growth of maize, but inhibited root mycorrhizal infection and plant phosphorus uptake, and led to the accumulation of zinc in plants. ZnO NPs and high phosphorus supply decreased root mycorrhizal infection, but AM inoculation significantly promoted plant growth under all phosphorus supply levels. Phosphorus application and AM inoculation increased soil pH, but reduced the bioavailability of Zn derived from ZnO NPs, decreased the translocation and accumulation of zinc in maize shoots, and thus produced beneficial effects on plants. In general, AM inoculation showed positive mycorrhizal effect, especially under low phosphorus conditions and addition of ZnO NPs. Our results showed for the first time that both AM fungi and phosphate fertilizer could help to mitigate soil pollution and the ecological and health risks posed by ZnO NPs.