Glyphosate and mycorrhization induce changes in plant growth and in root morphology and architecture in pepper plants (Capsicum annuum L.)

Abstract

SummaryMycorrhizal symbiosis is the mutually beneficial association between the roots of most land plants and many soil fungi. Glyphosate is the most commonly used herbicide for effective control of weeds. This broad-spectrum herbicide is exuded by the roots of treated crops and by senescing weeds, and absorbed by new crops, affecting their growth. We therefore examined the effects of glyphosate residues in the soil, and mycorrhization, on plant growth and root morphology in Capsicum annuum L. Plants were either non-inoculated or inoculated with Glomus mosseae, and grown with different concentrations of glyphosate in soil. Pepper plants grown without glyphosate behaved as mycotrophic species. At high doses, glyphosate (6.32 µM) reduced the extent of root colonisation (to 34%) and the percentage of arbuscule formation (to 50%), and inhibited vesicle formation. Alkaline phosphatase activity was not affected by the herbicide. Inoculated plants had a higher biomass, total height, and leaf area. At the highest concentrations, glyphosate-inoculated plants had double the biomass of non-inoculated plants. Chlorophyll and leaf protein contents were higher in inoculated than in non-inoculated plants at all glyphosate concentrations tested. Inoculated plants increased their root area by approx. 50% with or without glyphosate. The interaction of mycorrhization and glyphosate reduced the mitotic index, mitotic activity, and cell length in the root apices. The highest concentration of herbicide inhibited root branching, modified root morphology and root architecture, and affected growth parameters. Pepper plants tolerate high concentrations of glyphosate in the soil. Mycorrhization benefits plant growth and increases the root area, with a high number of lateral roots, regardless of herbicide concentration. Mycorrhization would be a favourable strategy to allow plants to cope with this abiotic stress condition.