Changes in the accumulation of shikimic acid in mycorrhized Capsicum annuum L. grown with application of glyphosate and phosphorus

Abstract

When glyphosate is added to the soil, it is absorbed by roots and transported by xylem causing growth inhibition in plants. Mycorrhiza is the beneficial association between roots of most plants and soil fungi. The methylphosphonic group of the glyphosate could compete with inorganic phosphates for sorption sites in the soil. The aim of this work was to study the effect of phosphorus availability and glyphosate residues in soil on pepper plant growth, and on physiological parameters, in plants non-inoculated or inoculated with Glomus mosseae or G. intraradices. The phytotoxic effects of the glyphosate were assessed by a bio-indicator as shikimic acid. At high doses, glyphosate (6.32 μM) reduced root colonization, and this effect was increased by higher levels of phosphorus in the soil. The effects of herbicide on shikimic acid accumulation and on shoot growth began 24 hours after glyphosate treatments (HAT). At 24, 48, and 72 HAT, inoculated plants grown without glyphosate showed higher growth compared to the non-inoculated ones. At high glyphosate (6.32 μM) and 96 HAT, the growth was completely inhibited. The shikimic acid accumulated in the upper leaves of non-inoculated plants, treated at 3.16 μM glyphosate, was significantly higher at high P level, related to inoculated ones. These results suggest that the remobilization of glyphosate residues in the soil by the addition of phosphate should be considered a serious problem for crops in treated soils. The mycorrhization increases the pepper plant's tolerance to high glyphosate concentration in the substrate, and may allow support to this stress condition.