Abstract
Arbuscular mycorrhizal fungi are among the most ubiquitous soil plant-symbiotic fungi in terrestrial environments and can alleviate the toxic effects of various contaminants on plants. As an essential micronutrient for higher plants, molybdenum (Mo) can cause toxic effects at excess levels. However, arbuscular mycorrhizal fungal impacts on plant performance and Mo accumulation under Mo-contamination still require to be explored. We first studied the effects of Claroideoglomus etunicatum BEG168 on plant biomass production and Mo accumulation in a biofuel crop, sweet sorghum, grown in an agricultural soil spiked with different concentrations of MoS2. The results showed that the addition of Mo produced no adverse effects on plant biomass, N and P uptake, and root colonization rate, indicating Mo has no phytotoxicity and fungitoxicity at the test concentrations. The addition of Mo did not increase and even decreased S concentrations in plant tissues. Arbuscular mycorrhizal inoculation significantly enhanced plant biomass production and Mo concentrations in both shoots and roots, resulting in increased Mo uptake by mycorrhizal plants. Overall, arbuscular mycorrhizal inoculation promoted the absorption of P, N and S by sweet sorghum plants, improved photosystem (PS) II photochemical efficiency and comprehensive photosynthesis performance. In conclusion, MoS2 increased Mo accumulation in plant tissues but produced no toxicity, while arbuscular mycorrhizal inoculation could improve plant performance via enhancing nutrient uptake and photochemical efficiency. Sweet sorghum, together with arbuscular mycorrhizal fungi, shows a promising potential for phytoremediation of Mo-contaminated farmland and revegetation of Mo-mine disturbed areas, as well as biomass production on such sites.
Highlights
Molybdenum (Mo) is a transition metal with low abundance in the lithosphere, but has wide applications in many economic sectors, such as alloy, electronic parts, lubricants, catalysts, and agricultural production [1]
Our ultimate aims are to verify whether AMF can improve the performance of sweet sorghum, and to know their potential for biomass production and revegetation or phytoremediation of MoS2 -contaminted sites
Maize plants grown in soil spiked with (NH4 )2 MoO4 accumulated up to 800 and 3000 mg/kg Mo in their shoots and roots respectively, and displayed typical toxic symptoms [21]. Because both sweet sorghum and maize belong to Gramineous species with similar Mo requirements, the differences in Mo accumulation between them could be ascribed to the bioavailability of the Mo added
Summary
Molybdenum (Mo) is a transition metal with low abundance in the lithosphere, but has wide applications in many economic sectors, such as alloy, electronic parts, lubricants, catalysts, and agricultural production [1]. Due to its high nutrition values and sugar-rich stalk, sweet sorghum is considered both an excellent forage crop and biofuel crop [19,20] It is of great significance for bioenergy production to study the growth of sweet sorghum on contaminated sites. Considering the importance of AMF in plant nutrition and tolerance, we hypothesize that AMF can improve plant performance of sweet sorghum in soil contaminated with MoS2. Using an agricultural soil spiked with MoS2 , we conducted a microcosm experiment to explore the growth and Mo uptake of sweet sorghum inoculated with or without AMF. Our ultimate aims are to verify whether AMF can improve the performance of sweet sorghum, and to know their potential for biomass production and revegetation or phytoremediation of MoS2 -contaminted sites
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