The influence of glyphosate on carotenoid pigments, reactive oxygen species scavenging enzymes and secondary stress metabolites within leaf tissue of three Acer species

Abstract

Glyphosate is a commonly used systemic herbicide in urban landscapes. Incidental spray drift and/or ground water contamination potentially represents an under-estimated problem that can detrimentally impact on the biology of trees. There are few studies that have investigated differences in tolerance of urban trees to glyphosate-induced oxidative stress. Aims of this study were to quantify the influence of a range of pigments carotenoids (lutein:β-carotene: neoxanthin:α-carotene, xanthophyll-cycle pigments (zeaxanthin:antheraxanthin: violaxanthin)), reactive oxygen species (ROS) scavenging enzymes (superoxide dismutase, calatase) and the stress metabolite proline within leaf tissue of three Acer species (Acer pseudoplatanus (sycamore), A. campestre (Field maple) and A. palmatum ‘Atropurpurea’ (Japanese maple)) widely planted into urban landscapes to identify the role these compounds play in protecting foliar tissue against glyphosate. Tolerance to glyphosate damage based on reductions in leaf chlorophyll content as a measure of leaf necrosis/chlorosis was in the order Acer pseudoplatanus>A. campestre>A. palmatum ‘Atropurpurea’. Quantitative analysis of carotenoid pigments, ROS scavenging enzymes and the stress metabolite proline demonstrated significant differences between the three Acer species. Highest concentrations of these compounds within leaf tissue was in the order Acer pseudoplatanus>A. campestre>A. palmatum ‘Atropurpurea’ which reflected order of tolerance based on leaf chlorophyll content loss. Results of this study indicate Acer species possess a suite of stress protective compounds with leaf tissue that potentially confer differing degrees of glyphosate tolerance. Quantification of the formation, concentration and fate of these enzymes and pigments may prove helpful in selecting trees with in-built capacity to tolerate glyphosate induced oxidative stress and allow professionals to make informed decisions regarding tree selection in urban areas where glyphosate is routinely used.