[Effects of mycorrhizal types on herbaceous species richness in forest ecosystem]. / èŒæ ¹ç±»åž‹å¯¹æ£®æž—è‰æœ¬æ¤ç‰©ç¾¤è½ç‰©ç§ä¸°å¯Œåº¦çš„å½±å“.

Species richness plays an important role in ecosystem stability and health. Mycorrhizal type is an important factor affecting ecological processes. How mycorrhizal types affect understory herb species richness and their responses to environmental changes remain largely unknown. We investigated the effects of mycorrhizal types on species richness and their responses to environmental change in understory herbaceous communities based on data of three mycorrhizal types of dominated trees (including 1604 arbuscular mycorrhiza (AM) trees, 4654 ectomycorrhiza (ECM) trees, and 5568 AM+ECM trees) and environmental factors in America. The results showed significant differences in species richness of herbaceous plant communities among different mycorrhizal types. Forests with higher dominance of AM plants tended to have higher herbaceous plant richness, supporting the mycorrhizal mediation hypothesis. The impacts of environmental factors (latitude, temperature, precipitation, nitrogen deposition, and soil characteristics) on species richness of herbaceous plant communities depended on mycorrhizal type of forests. The species richness of understory herbs in AM, ECM, and AM+ECM forests was mostly affected by nitrogen deposition, temperature, and soil pH, with the relative importance of 42.3%, 41.1% and 48.7%, respectively. Mycorrhizal types of dominant trees played a vital role in regulating the species richness of understory herbs and influenced their responses to environmental changes.

Arbuscular mycorrhizal fungi enhance active ingredients of medicinal plants: a quantitative analysis.

Medicinal plants are invaluable resources for mankind and play a crucial role in combating diseases. Arbuscular mycorrhizal fungi (AMF) are widely recognized for enhancing the production of medicinal active ingredients in medicinal plants. However, there is still a lack of comprehensive understanding regarding the quantitative effects of AMF on the accumulation of medicinal active ingredients. Here we conducted a comprehensive global analysis using 233 paired observations to investigate the impact of AMF inoculation on the accumulation of medicinal active ingredients. This study revealed that AMF inoculation significantly increased the contents of medicinal active ingredients by 27%, with a particularly notable enhancement observed in flavonoids (68%) and terpenoids (53%). Furthermore, the response of medicinal active ingredients in belowground organs (32%) to AMF was more pronounced than that in aboveground organs (18%). Notably, the AMF genus Rhizophagus exhibited the strongest effect in improving the contents of medicinal active ingredients, resulting in an increase of over 50% in both aboveground and belowground organs. Additionally, the promotion of medicinal active ingredients by AMF was attributed to improvements in physiological factors, such as chlorophyll, stomatal conductance and net photosynthetic rate. Collectively, this research substantially advanced our comprehension of the pivotal role of AMF in improving the medicinal active ingredients of plants and provided valuable insights into the potential mechanisms driving these enhancements.

Influence of Mycorrhiza on C:N:P Stoichiometry in Senesced Leaves.

Senesced leaves play a vital role in nutrient cycles in the terrestrial ecosystem. The carbon (C), nitrogen (N) and phosphorus (P) stoichiometries in senesced leaves have been reported, which are influenced by biotic and abiotic factors, such as climate variables and plant functional groups. It is well known that mycorrhizal types are one of the most important functional characteristics of plants that affect leaf C:N:P stoichiometry. While green leaves' traits have been widely reported based on the different mycorrhiza types, the senesced leaves' C:N:P stoichiometries among mycorrhizal types are rarely investigated. Here, the patterns in senesced leaves' C:N:P stoichiometry among plants associated with arbuscular mycorrhizal (AM), ectomycorrhizal (ECM), or AM + ECM fungi were explored. Overall, the senesced leaves' C, with 446.8 mg/g in AM plants, was significantly lower than that in AM + ECM and ECM species, being 493.1 and 501.4 mg/g, respectively, which was mainly caused by boreal biomes. The 8.9 mg/g senesced leaves' N in ECM plants was significantly lower than in AM (10.4 mg/g) or AM + ECM taxa (10.9 mg/g). Meanwhile, the senesced leaves' P presented no difference in plant associations with AM, AM + ECM and ECM. The senesced leaves' C and N presented contrary trends with the changes in mean annual temperature (MAT) and mean annual precipitation (MAP) in ECM or AM + ECM plants. The differences in senesced leaves' C and N may be more easily influenced by the plant mycorrhizal types, but not P and stoichiometric ratios of C, N and P. Our results suggest that senesced leaves' C:N:P stoichiometries depend on mycorrhizal types, which supports the hypothesis that mycorrhizal type is linked to the evolution of carbon-nutrient cycle interactions in the ecosystem.

[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.

Contribution of AM inoculation and cattle manure to lead and cadmium phytoremediation by tobacco plants.

Lead and cadmium are both highly toxic pollutants and pose potential risks to the environment and human health. Arbuscular mycorrhizal (AM) inoculation and organic amendments may make a potential contribution to phytoremediation of these toxic metals, but their effects remain unclear. We conducted a pot culture experiment to study the contribution of AM inoculation and/or cattle manure to phytoremediation of two soils artificially polluted with 0, 350, 500 and 1000 mg Pb per kg soil or 0, 1, 10, 100 mg Cd per kg soil using tobacco plants. Results showed that AM colonization was greatly reduced when exposed to more heavy metals especially Cd, whereas organic amendment alleviated metal stress and showed protective effects. In general, AM inoculation and cattle manure, singly or in combination, all significantly increased tobacco growth and Pb and Cd accumulation in shoots and roots, while decreased DTPA-extractable Pb and Cd concentrations in soil, and combination treatments (MN) produced the most pronounced positive effects. Improved plant P nutrition, higher soil pH and lower available metal concentrations contributed by AM inoculation and/or organic amendment may be the main strategies to alleviate metal toxicity and enhance phytoremediation efficiency. Our results indicate that AM fungi and organic manure play a synergistic positive role both in phytoextraction and phytostabilization of Cd and Pb.

Inoculations with arbuscular mycorrhizal fungi increase vegetable yields and decrease phoxim concentrations in carrot and green onion and their soils.

BACKGROUND: As one of the most widely used organophosphate insecticides in vegetable production, phoxim (C(12)H(15)N(2)O(3)PS) is often found as residues in crops and soils and thus poses a potential threat to public health and environment. Arbuscular mycorrhizal (AM) fungi may make a contribution to the decrease of organophosphate residues in crops and/or the degradation in soils, but such effects remain unknown. METHODOLOGY/PRINCIPAL FINDINGS: A greenhouse pot experiment studied the influence of AM fungi and phoxim application on the growth of carrot and green onion, and phoxim concentrations in the two vegetables and their soil media. Treatments included three AM fungal inoculations with Glomus intraradices BEG 141, G. mosseae BEG 167, and a nonmycorrhizal control, and four phoxim application rates (0, 200, 400, 800 mg l(-1), while 400 mg l(-1) rate is the recommended dose in the vegetable production system). Carrot and green onion were grown in a greenhouse for 130 d and 150 d. Phoxim solution (100 ml) was poured into each pot around the roots 14d before plant harvest. Results showed that mycorrhizal colonization was higher than 70%, and phoxim application inhibited AM colonization on carrot but not on green onion. Compared with the nonmycorrhizal controls, both shoot and root fresh weights of these two vegetables were significantly increased by AM inoculations irrespective of phoxim application rates. Phoxim concentrations in shoots, roots and soils were increased with the increase of phoxim application rate, but significantly decreased by the AM inoculations. Soil phosphatase activity was enhanced by both AM inocula, but not affected by phoxim application rate. In general, G. intraradices BEG 141 had more pronounced effects than G. mosseae BEG 167 on the increase of fresh weight production in both carrot and green onion, and the decrease of phoxim concentrations in plants and soils. CONCLUSIONS/SIGNIFICANCE: Our results indicate a promising potential of AM fungi for enhancing vegetable production and reducing organophosphorus pesticide residues in plant tissues and their growth media, as well as for the phytoremediation of organophosphorus pesticide-contaminated soils.

Dynamics of phoxim residues in green onion and soil as influenced by arbuscular mycorrhizal fungi.

Organophosphorus pesticides in crops and soil pose a serious threat to public health and environment. Arbuscular mycorrhizal (AM) fungi may make a contribution to organophosphate degradation in soil and consequently decrease chemical residues in crops. A pot culture experiment was conducted to investigate the influences of Glomus caledonium 90036 and Acaulospora mellea ZZ on the dynamics of phoxim residues in green onion (Allium fistulosum L.) and soil at different harvest dates after phoxim application. Results show that mycorrhizal colonization rates of inoculated plants were higher than 70%. Shoot and root fresh weights did not vary with harvest dates but increased significantly in AM treatments. Phoxim residues in plants and soil decreased gradually with harvest dates, and markedly reduced in AM treatments. Kinetic analysis indicated that phoxim degradation in soil followed a first-order kinetic model. AM inoculation accelerated the degradation process and reduced the half-life. G. caledonium 90036 generally produced more pronounced effects than A. mellea ZZ on both the plant growth and phoxim residues in plants and soil. Our results indicate a promising potential of AM fungi for the control of organophosphate residues in vegetables, as well as for the phytoremediation of organophosphorus pesticide-contaminated soil.

[Influence of arbuscular mycorrhizal inoculation on growth and phoxim residue of carrot (Daucus carota L.)].

A pot culture experiment was carried out to study the influence of arbuscular mycorrhizal (AM) fungi on the growth and phoxim residue of carrot (Daucus carota L). Four levels of phoxim (0, 200, 400, 800 mg x L(-1)) and two AM fungal inocula, Glomus intraradices BEG 141(141), Glomus mosseae BEG 167 (167),and one nonmycorrhizal inoculum (CK), were applied to the sterilized soil. The plants were harvested after 5 months of growth and phoxim was irrigated into the root zone 14 d before plant harvest. Although decreasing with the increase of phoxim dosage, root infection rates of all the mycorrhizal plants were higher than 70%. Phoxim showed no significant dose effect on shoot wet weights and root yields, which were all increased by AM inoculation at four phoxim dosages. Phoxim residues in shoots and roots increased with the increase of phoxim dosage, but decreased by AM inoculation. In general, Glomus intraradices BEG 141 showed more pronounced effects on the growth and phoxim residue of carrot than Glomus mosseae BEG 167 did. Our results show a promising potential of AM fungi in carrot production and controlling pesticide residues.