The modulation of sugarcane growth and nutritional profile under aluminum stress is dependent on beneficial endophytic bacteria and plantlet origin

Plant growth-promoting bacteria (PGPB) are claimed to not only improve plant fitness but also alleviate plant stress. In this study, we evaluated the effect of five PGPB strains on plantlet growth and nutrient and aluminum (Al) uptake under acid soil conditions characterized by low P and K nutrient availability and high metal and aluminum (Al) bioavailability, which may represent a stress condition for crop plants. The PGPB strains were inoculated in sugarcane plantlets produced by meristem tissue culture (MCPs) or one-bud stalks (O-BSPs) and cultivated in soil at 37% Al saturation and pH 4.0. Biomass accumulation and Al and nutrient content in roots and shoots were determined after 30 days of growth. Bacterial inoculation increased root and shoot biomass. However, the magnitudes of these increases were dependent on bacterial strain and plantlet origin. The inoculated plantlets exhibited increased Al content and shifts in Al allocation and calcium (Ca) and boron (B) content among different plant parts (root or shoot), and these changes also depended on plantlet origin and the inoculated strain. The higher Ca uptake of inoculated MCPs and higher B uptake of inoculated O-BSPs may have contributed to reducing the damage caused by excessive Al content. The beneficial microbes also caused changes in plant uptake of micronutrients and slightly reduced macronutrient content. Pseudomonas fluorescens (IAC/BECa 141), Kosakonia radicincitans (IAC/BECa 95), Paraburkholderia tropica (IAC/BECa 135) and Herbaspirillum frisingense (IAC/BECa 152) showed potential for alleviating Al stress in sugarcane plantlets

Cadmium Accumulation In Sunflower Plants Influenced By Arbuscular Mycorrhiza

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 μmol L-1) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg-1. Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 μg g-1 dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues. Copyright © Taylor & Francis Group, LLC.101113Andrade, S.A.L., Abreu, C.A., de Abreu, M.F., Silveira, A.P.D., Interação de chumbo, da saturação por bases do solo e de micorriza arbuscular no crescimento e nutrição mineral da soja. (2003) Rev. Bras. Ci. Solo, 27, pp. 945-954Andrade, S.A.L., Abreu, C.A., de Abreu, M.F., Silveira, A.P.D., Influence of lead addition on arbuscular mycorrhiza and Rhizobium symbioses under soybean plants (2004) Appl. Soil Ecol, 26, pp. 123-131Andrade, S.A.L., de Abreu, M.F., Jorge, R.A., Silveira, A.P.D., Cadmium effect on the association of jackbean (Canavalia ensiformis) and arbuscular mycorrhizal fungi (2005) Scientia Agricola, 62, pp. 389-394Baker, A.M.J., McGrath, S.P., Reeves, R.D., Smith, J.A.C., Metal hyperaccumulator plants: A review of the ecology and the physiology of a biochemical resource for phytoremediation of metal polluted soil (2000) Phytoremediation of Contaminated Soil and Water, pp. 85-107. , Terry, N. and Bañuelos, G, Eds, Boca Raton, Florida, LewisBazzaz, F.A., Rolfe, G.L., Carlson, R.W., Effect of cadmium on photosynthesis and transpiration of excised leaves of corn and sunflower (1992) Physiol. 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Tolerance And Phytoremediation Potential Of Stizolobium Aterrimum Associated To The Arbuscular Mycorrhizal Fungi Glomus Etunicatum In Leadcontaminated Soil [tolerância E Potencial Fitorremediador De Stizolobium Aterrimum Associada Ao Fungo Micorrízico Arbuscular Glomus Etunicatum Em Solo Contaminado Por Chumbo]

Heavy metal pollution of soils has increased significantly in the last years owing to anthropic action. Several techniques can be used to revert or to minimize soil contamination, although many of these techniques are harmful to the soil. An alternative is to use a new technique, called phytoremediation, based on the ability of plants to take up elements from soils with excessive high levels of metals or of other potentially toxic elements and thus contribute to soil decontamination. The inoculation of plants with arbuscular mycorrhizal fungi (AMF) can influence the absorption of these elements. The phytoremediation potential of Stizolobium aterrimum plants with or without AMF in soils with increasing lead concentrations was evaluated in a greenhouse experiment, in a 4 x 2 factorial design. The treatments consisted of the addition of four Pb rates (0, 250, 500 and 1000 mg dm-3) to the soil where black velvet bean plants associated or not with Glomus etunicatum AMF where grown. The results showed that black velvet bean was Pb tolerant at the tested rates. The association with AMF did not influence the Pb plant uptake. However, the mycorrhiza influenced biological nitrogen fixation by increasing the activity of the enzyme nitrogenase in mycorrhizal plants. 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Eucalypt species drive rhizosphere bacterial and fungal community assembly but soil phosphorus availability rearranges the microbiome

Soil phosphorus (P) availability may limit plant growth and alter root-soil interactions and rhizosphere microbial community composition. The composition of the rhizosphere microbial community can also be shaped by plant genotype. In this study, we examined the rhizosphere microbial communities of young plants of 24 species of eucalypts (22 Eucalyptus and two Corymbia species) under low or sufficient soil P availability. The taxonomic diversity of the rhizosphere bacterial and fungal communities was assessed by 16S and 18S rRNA gene amplicon sequencing. The taxonomic modifications in response to low P availability were evaluated by principal component analysis, and co-inertia analysis was performed to identify associations between bacterial and fungal community structures and parameters related to plant growth and nutritional status under low and sufficient soil P availability. The sequencing results showed that while both soil P availability and eucalypt species influenced the microbial community assembly, eucalypt species was the stronger determinant. However, when the plants are subjected to low P-availability, the rhizosphere selection became strongest. In response to low P, the bacterial and fungal communities in the rhizosphere of some species showed significant changes, whereas in others remained relatively constant under low and sufficient P. Co-inertia analyses revealed a significant co-dependence between plant nutrient contents and bacterial and fungal community composition only under sufficient P. By contrast, under low P, bacterial community composition was related to plant biomass production. In conclusion, our study shows that eucalypt species identity was the main factor modulating rhizosphere microbial community composition; significant shifts due to P availability were observed only for some eucalypt species