Selenium uptake and accumulation in winter wheat as affected by level of phosphate application and arbuscular mycorrhizal fungi

Influence of arbuscular mycorrhizal fungi on selenium uptake by winter wheat depends on the level of selenate spiked in soil

Arbuscular mycorrhizal fungi increase the bioavailability and wheat (Triticum aestivum L.) uptake of selenium in soil

The aim of this study is to investigate the effects of arbuscular mycorrhizal fungi (AMF) on garlic plants growth and the uptake of selenium (Se). Garlic plants were grown in the pots inoculated with Glomus fasciculatum and G. mosseae and maintained in a greenhouse. Three weeks after planting, the pots had received different concentrations of Se (5, 10, 15, 20, 25 mg kg−1 of soil) in the form of selenium dioxide (SeO2) at 3 weeks intervals up to 12 weeks. For physiological and biochemical analysis, the samples were randomly collected from five plants of each experiment. Maximum AM infection, spore population and plant biomass were observed in the roots of mycorrhizal-mediated plants without Se, and they were gradually declined in both mycorrhizal and non-mycorrhizal (NM) plants with increasing concentrations of Se. Among the two Glomus species tested, G. fasciculatum-mediated plants showed higher AM infection, spore population and plant biomass than G. mosseae. No differences were observed for the uptake of Se in mycorrhizal plants and NM plants. However, NM plants uptake more Se than mycorrhizal plants. Higher contents of total chlorophyll and sugars were observed in plants inoculated with G. fasciculatum without Se and they were decreased in the presence of Se. In contrast, increased amount of glutathione peroxidase was observed at increasing concentrations of Se up to 20 mg kg−1. High-performance liquid chromatography data revealed that SeO2 converted to organic form of Se as γ-glutamyl-Se-methylselenocysteine. These results are basis for further investigations on the role of AMF on plant growth and uptake of Se in crop plants.

Communities of plants, biological soil crusts (BSCs), and arbuscular mycorrhizal (AM) fungi are known to influence soil stability individually, but their relative contributions, interactions, and combined effects are not well understood, particularly in arid and semiarid ecosystems. In a landscape-scale field study we quantified plant, BSC, and AM fungal communities at 216 locations along a gradient of soil stability levels in southern Utah, USA. We used multivariate modeling to examine the relative influences of plants, BSCs, and AM fungi on surface and subsurface stability in a semiarid shrubland landscape. Models were found to be congruent with the data and explained 35% of the variation in surface stability and 54% of the variation in subsurface stability. The results support several tentative conclusions. While BSCs, plants, and AM fungi all contribute to surface stability, only plants and AM fungi contribute to subsurface stability. In both surface and subsurface models, the strongest contributions to soil stability are made by biological components of the system. Biological soil crust cover was found to have the strongest direct effect on surface soil stability (0.60; controlling for other factors). Surprisingly, AM fungi appeared to influence surface soil stability (0.37), even though they are not generally considered to exist in the top few millimeters of the soil. In the subsurface model, plant cover appeared to have the strongest direct influence on soil stability (0.42); in both models, results indicate that plant cover influences soil stability both directly (controlling for other factors) and indirectly through influences on other organisms. Soil organic matter was not found to have a direct contribution to surface or subsurface stability in this system. The relative influence of AM fungi on soil stability in these semiarid shrublands was similar to that reported for a mesic tallgrass prairie. Estimates of effects that BSCs, plants, and AM fungi have on soil stability in these models are used to suggest the relative amounts of resources that erosion control practitioners should devote to promoting these communities. This study highlights the need for system approaches in combating erosion, soil degradation, and arid-land desertification.

The influence of arbuscular mycorrhizal (AM) fungi on aggregate stability of a semi-arid Indian vertisol was studied in a pot experiment in which Sorghum bicolor (L.) was grown as test plant for 10 weeks. Pasteurized soil inoculated with AM fungi was studied with pasteurized and unpasteurized soils as references. A part of the soil in each pot was placed in nylon mesh bags to separate effects of roots and hyphae. The sorghum plants were planted outside the mesh bags which permitted AM hyphae to enter while excluding roots. Aggregate stability of the soil was determined by wet-sieving and turbidimetric measurements. Development of the AM fungi was quantified as colonized root length and external hyphal length. Soil exposed to growth of roots and hyphae (outside mesh bags) showed aggregates with larger geometric mean diameter (GMD) in pasteurized soil inoculated with AM fungi than in pasteurized uninoculated soil. There was no significant difference in GMD of the inoculated, pasteurized soil and the unpasteurized soil. No significant effects of inoculation or plant growth were found in pasteurized soil exposed to hyphal growth only (inside the mesh bags). However, the unpasteurized soil had significantly higher GMD than the pasteurized soil, irrespective of plants and inoculum. Turbidimetric measurements of soil exposed to roots and hyphae (outside mesh bags) showed the highest aggregate stability for the inoculated pasteurized soil. These results demonstrate that AM fungi contribute to the stabilization of soil aggregates in a vertisol, and that the effect is significant after only one growing season. The effect was associated with both AM hyphae and the stimulation of root growth by AM fungi. The contribution from plant roots and AM hyphae to aggregate stability of different size fractions is discussed.

Selenium (Se) is an essential micronutrient for humans and animals, but not for plants. Generally, cereals including wheat and rice are the main source of dietary Se for humans. Although arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microbes and commonly develop symbionts with winter wheat (Triticum aestivum L.), the influence of AMF on accumulation and translocation of Se during developmental cycle of winter wheat is still unclear. Based on a pot trial, the present results indicated that the effects of AMF on grain Se concentration in winter wheat depend on the Se species spiked in the soil and that Rhizophagus intraradices (Ri) significantly enhanced grain Se concentration under selenite treatment. Moreover, inoculation of AMF significantly increased grain Se content under selenite and selenate treatments. The enhanced grain Se content of mycorrhizal wheat could be attributed to (i) apparently increased root growth of mycorrhizal wheat at jointing could absorb more Se for translocating to aerial tissues and consequently result in significantly higher stalk Se content and (ii) enhancing Se translocation from vegetative tissues to grains. The present study showed that AMF significantly (P < 0.05) increased pre-anthesis Se uptake under selenate treatment and post-anthesis Se uptake under selenite treatment. The present study indicated the feasibility of inoculation of AMF for increasing grain Se concentration under selenite treatment and enhancing the efficiency of biofortification of Se under selenate treatments. © 2022 Society of Chemical Industry.

Ubiquitous in agronomic ecosystems, arbuscular mycorrhizal fungi (AMF) readily colonize winter wheat (Triticum aestivum L.), but the mechanisms of the fungi related to selenium (Se) uptake by the crop are still unclear. Wheat seedlings were inoculated with Glomus versiform or Funneliformis mosseae for 8 weeks. Both concentration- and time-dependent Se uptake in wheat colonized by AMF were investigated in hydroponic experiments supplied with selenate, selenite, or selenomethionine. Pot trials were also conducted to investigate the influence of mycorrhizal inoculation on the accumulation of Se in wheat. The present study showed that AMF had a significant (P < 0.001) effect on selenate and selenite uptake by the wheat roots in hydroponic experiments, but not for selenomethionine. Vmax for selenate and selenite uptake by mycorrhizal roots was increased by more than 1.85 times than those by non-mycorrhizal roots, from 55.93 to 179.6 nmol g−1 d.w. h−1 for selenate and from 860.3 to 1688 nmol g−1 d.w. h−1 for selenite. Pot trials further showed that inoculation with AMF significantly (P < 0.05) enhanced Se accumulation in shoots and roots either in selenate- or selenite-spiked soils. Mycorrhizal inoculation significantly increased uptake of selenate and selenite by increasing the valid absorption area of roots, including specific root surface area, specific root length, and specific number of tips for Se uptake. The present study also suggested that AM symbiosis can improve wheat Se acquisition through up-regulating the expression of TaSultr1;1, TaSultr1;3, and TaSultr2;1 in the plant roots, especially TaSultr1;1. The enhanced Se uptake in the mycorrhizal roots benefits Se accumulation in wheat, indicating the potential of AMF to increase grain Se concentrations of wheat and to improve the diet of residents living on wheat as their staple food.

Arbuscular mycorrhizal (AM) fungi can influence all components of plant reproduction including pollen delivery, pollen germination, pollen tube growth, fertilization, and seed germination. AM fungi associate with plant roots, uptake nutrients, and prime plants for faster defense responses. Our literature review first identified four testable hypotheses describing how AM fungi could alter pollen delivery: (1) We hypothesize AM fungi promote floral display size. The influence of AM fungi on flower size and number is supported by literature, however there are no studies on floral color. (2) We hypothesize AM fungi promote pollen and nectar quality and quantity, and, as reported before, AM fungi promote male fitness over female fitness. (3) We hypothesize AM fungi promote both earlier and longer flowering times, but we found no consistent trend in the data for earlier or later or longer flowering times. (4) We hypothesize AM fungi alter floral secondary chemistry and VOCs, and find there is clear evidence for the alteration of floral chemistry but little data on VOCs. Second, we focus on how AM fungi could alter pollen germination, pollen tube growth, and fertilization, and present three testable hypotheses. We found evidence that AM fungi influence pollen germination and pollen tube growth, production of seeds, and seed germination. However, while most of these influences are positive they are not conclusive, because studies have been conducted in small numbers of systems and groups. Therefore, we conclude that the majority of research to date may not be measuring the influence of AM fungi on the most important components of plant reproduction: pollen germination, pollen tube growth, fertilization, and seed germination.

Purpose – Partial least squares (PLS) path modeling has become a pivotal empirical research method in international marketing. Owing to group comparisons' important role in research on international marketing, we provide researchers with recommendations on how to conduct multigroup analyses in PLS path modeling. Methodology/approach – We review available multigroup analysis methods in PLS path modeling and introduce a novel confidence set approach. A characterization of each method's strengths and limitations and a comparison of their outcomes by means of an empirical example extend the existing knowledge of multigroup analysis methods. Moreover, we provide an omnibus test of group differences (OTG), which allows testing the differences across more than two groups. Findings – The empirical comparison results suggest that Keil et al.'s (2000) parametric approach can generally be considered more liberal in terms of rendering a certain difference significant. Conversely, the novel confidence set approach and Henseler's (2007) approach are more conservative. Originality/value of paper – This study is the first to deliver an in-depth analysis and a comparison of the available procedures with which to statistically assess differences between group-specific parameters in PLS path modeling. Moreover, we offer two important methodological extensions of existing research (i.e., the confidence set approach and OTG). This contribution is particularly valuable for international marketing researchers, as it offers recommendations regarding empirical applications and paves the way for future research studies aimed at comparing the approaches' properties on the basis of simulated data.

Robinia pseudoacacia L. (black locust) is a widely planted tree species on Loess Plateau for revegetation. Due to its symbiosis forming capability with arbuscular mycorrhizal (AM) fungi, we explored the influence of arbuscular mycorrhizal fungi on plant biomass, root morphology, root tensile strength and soil aggregate stability in a pot experiment. We inoculated R. pseudoacacia with/without AM fungus (Rhizophagus irregularis or Glomus versiforme), and measured root colonization, plant growth, root morphological characters, root tensile force and tensile strength, and parameters for soil aggregate stability at twelve weeks after inoculation. AM fungi colonized more than 70% plant root, significantly improved plant growth. Meanwhile, AM fungi elevated root morphological parameters, root tensile force, root tensile strength, Glomalin-related soil protein (GRSP) content in soil, and parameters for soil aggregate stability such as water stable aggregate (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD). Root length was highly correlated with WSA, MWD and GMD, while hyphae length was highly correlated with GRSP content. The improved R. pseudoacacia growth, root tensile strength and soil aggregate stability indicated that AM fungi could accelerate soil fixation and stabilization with R. pseudoacacia, and its function in revegetation on Loess Plateau deserves more attention.

Partial least squares (PLS) path modeling is a variance-based structural equation modeling technique that is widely applied in business and social sciences. It is the method of choice if a structural equation model contains both factors and composites. This chapter aggregates new insights and offers a fresh look at PLS path modeling. It presents the newest developments, such as consistent PLS, confirmatory composite analysis, and the heterotrait-monotrait ratio of correlations (HTMT). PLS path modeling can be regarded as an instantiation of generalized canonical correlation analysis. It aims at modeling relationships between composites, i.e., linear combinations of observed variables. A recent extension, consistent PLS, makes it possible to also include factors in a PLS path model. The chapter illustrates how to specify a PLS path model consisting of construct measurement and structural relationships. It also shows how to integrate categorical variables. A particularly important consideration is model identification: Every construct measured by multiple indicators must be embedded into a nomological net, which means that there must be at least one other construct with which it is related. PLS path modeling results are useful for exploratory and confirmatory research. The chapter provides guidelines for assessing the fit of the overall model, the reliability and validity of the measurement model, and the relationships between constructs. Moreover, it provides a glimpse on various extensions of PLS, many of which will be described in more detail in later chapters of the book.

Transcriptome and metabolome analyses reveal the promoting effects of arbuscular mycorrhizal fungi on selenium uptake in grapevines.

Thermal infrared imaging technology was used to understand the effects of arbuscular mycorrhizal fungi (AMF) and dark septate endophytic (DSE) fungi, both separately and together, on plant growth and physiological status, and to screen and develop efficient microbial agents in a pot experiment design. Eight treatments comprised the control (CK), AMF inoculation alone, DSE fungal treatments (DSE20%, DSE40% and DSE80%; 2, 4, 8 × 105 CFU mL−1) and combined inoculation treatments (DSE20% + AMF, DSE40% + AMF, and DSE80% + AMF). Canopy temperature (Tcanopy) and stomatal conductance (gs) were monitored at different growth stages, and plant biomass-related indicators were obtained at harvest. These indicators were used to assess plant growth and the physiological status resulting from the different inoculation treatments. During plant growth, the plant Tcanopy decreased following inoculation. Differences in Tcanopy between control and inoculated plants were detected by thermal infrared imaging technology and were −3.8 to + 9.3 °C (control–inoculation treatment). Growth index and Tcanopy monitoring indicate that the growth-promoting effect of combined inoculation was higher than that of either fungal type alone, with DSE80% + AMF producing the highest growth promotion. During the growth process of inoculated maize, the effect of inoculated AMF on the physiological condition of maize growth can be better monitored by thermal infrared at 10 a.m., 12 p.m., 2 p.m. and 4 p.m. on the 31st–57th days of the growth period. The method and results of this experiment are conducive to the rapid and efficient monitoring of the effects of microorganisms on plant growth and physiological status and can be applied to the screening, application, and promotion of microbial agents.

Arbuscular mycorrhizal fungi alleviate elevated temperature and nitrogen deposition- induced warming potential by reducing soil N2O emissions in a temperate meadow

To investigate the influences of AM fungi(Glomus intraradicesand Glomus mosseae) on the resistance of tobacco to bacterial wilt(R. solan), a pot experiment was conducted to study the influences of AM fungi inoculation on the bacterial wilt disease incidence, the activity of peroxidase(POD) related to disease resistance and MDA content. The results showed that comparing with the CK, AM fungi inoculation could promote the growth of tobacco plants, the dry weight of and P content in tobacco shoot and roots, and N content in tobacco shoot increased significantly, and the disease incidence and index of bacterial wilt reduced. After R. solan inoculating, the POD activity of tobacco leaves inoculated with Glomus intraradices and Glomus mosseae increased by 22.9% and 26.9% respectively, compared with the CK(only inoculated with R. solan); meanwhile, MDA content declined; which indicated that AM fungi could promote the resistance of tobacco to bacterial wilt.