Glyphosate-induced structural variations in Commelina erecta L. (Commelinaceae)

Abstract

The purpose of this study was to analyze the structural variations of Commelina erecta, a glyphosate-tolerant weed, produced by this herbicide. Regrowth shoots (vegetative cloning axes) and seedlings and two glyphosate concentrations: 900 and 1800 grams of acid equivalent per hectare (g a.e. ha−1) were used. The following variations were observed: foliar shape and size changes, changes in the length of internodes, variations in the quantity of inflorescences, low seed production, and differences in the number of branches. After treatment, different phenotypic responses were observed as a result of differential sensitivity to glyphosate. Most of the vegetatively-propagated plants treated with 900 g a.e. ha−1 revealed the same morphological structure as that of controls (i.e. three clearly identifiable zones: a basal or branching zone, a middle zone where branch production is inhibited, and an apical zone where only floral branches are produced). By contrast, the 900 g a.e. ha−1 treated seedlings and the 1800 g a.e. ha−1 treated regrowth shoots and seedlings showed two phenotypic responses, exhibiting differences in the quantity and location of branches and in the survival time of axes. The main variation is seen in branch production in the region that is usually inhibited. The different phenotypic responses and morphological changes suggest that C. erecta shows a very high intraspecific variability, which allows it to survive and thrive even in environments with intensive glyphosate application. These results underscore the need to solve the problem of tolerant weeds by means of an integrated approach including alternative management practices grounded on knowledge of the species and their behavior.