Compatibility of Azospirillum brasilense with Pesticides Used for Treatment of Maize Seeds
INTERNATIONAL JOURNAL OF MICROBIOLOGY
Authors: Santos, Mariana S.; Rondina, Artur B. L.; Nogueira, Marco A.; Hungria, Mariangela
Abstract
Seed treatment with chemical pesticides is commonly used as an initial plant protection procedure against pests and diseases. However, the use of such chemicals may impair the survival and performance of beneficial microorganisms introduced via inoculants, such as the plant growth-promoting bacteriumAzospirillum brasilense. We assessed the compatibility between the most common pesticide used in Brazil for the treatment of maize seeds, composed of two fungicides, and one insecticide, with the commercial strains Ab-V5 and Ab-V6 ofA. brasilense, and evaluated the impacts on initial plant development. The toxicity of the pesticide toA. brasilensewas confirmed, with an increase in cell mortality after only 24 hours of exposurein vitro. Seed germination and seedling growth were not affected neither by theA. brasilensenor by the pesticide. However, under greenhouse conditions, the pesticide affected root volume and dry weight and root-hair incidence, but the toxicity was alleviated by the inoculation withA. brasilensefor the root volume and root-hair incidence parameters. In maize seeds inoculated withA. brasilense, the pesticide negatively affected the number of branches, root-hair incidence, and root-hair length. Therefore, new inoculant formulations with cell protectors and the development of compatible pesticides should be searched to guarantee the benefits of inoculation with plant growth-promoting bacteria.
Role of chemical pressure on the electronic and magnetic properties of the spin-1/2 kagome mineral averievite
PHYSICAL REVIEW B
Authors: Dey, Dibyendu; Botana, Antia S.
Abstract
We investigate the electronic and magnetic properties of the kagome mineral averievite (CsC1)Cu5V2O10 and its phosphate analog (CsC1)Cu5P2O10 using first-principles calculations. The crystal structure of these compounds features Cu2+ kagome layers sandwiched between Cu2+P5+/Cu2+-V5+ honeycomb planes, with pyrochlore slabs made of corner-sharing Cu tetrahedra being formed. The induced chemical pressure effect upon substitution of V by P causes significant changes in the structure and magnetic properties. Even though the in-plane antiferromagnetic (AFM) coupling J(1) within the kagome layer is similar in the two materials, the interplane AFM coupling J(2) between kagome and honeycomb layers is five times larger in the P variant, increasing the degree of magnetic frustration in the constituting Cu tetrahedra.
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