Abstract
Glyphosate is the most widely used herbicide in the world. In sugarcane, it is used as a herbicide when applied at its field rate, but it is also used as ripener when applied as low doses. However, the effects of glyphosate on plant metabolism and sugarcane growth are not fully understood. This study aimed to evaluate the metabolic changes and the effects on sugarcane plant growth caused by the application of different doses of glyphosate. Sugarcane plants were grown in a greenhouse and subjected to glyphosate applications at doses of 7.2; 18; 36; 72; 180; 360 and 720 g a.e. ha-1. Plants grown without an herbicide application were used as a control. Plants from each treatment were collected at 2, 7, 14, and 21 days after treatment (DAT) application to quantify the levels of shikimic acid, quinic acid, shikimate-3-phosphate, glyphosate, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), phenylalanine, tyrosine, and tryptophan. Visual evaluations of plant intoxication were performed at the same time as the collection of plants, and the quantification of their shoot dry biomass was performed at 21 DAT. At doses of glyphosate greater than 72 g a.e. ha-1, increases in the levels of shikimic acid, quinic acid, and shikimate-3-phosphate occurred and AMPA was detected in the plants. Initially, glyphosate caused increases in the plant levels of phenylalanine and tyrosine at doses of 72 and 180 g a.e. ha-1, although a decrease in the levels of aromatic amino acids subsequently occurred at and above the doses of 72 or 180 g a.e. ha-1. The doses ranging from 7.2 to 36 g a.e. ha-1 promoted an increase in plant shoot biomass, and doses greater than 72 g a.e. ha-1 caused significant reductions in dry mass.
Highlights
Brazil is the world’s largest sugarcane (Saccharum spp.) producer, with a planted area of approximately 9.09 million hectares and a mean yield of 72.444 kg·ha−1 [1]
Over the course of the other periods evaluated, for the 720 g a.e. ha−1 dose, the level of glyphosate gradually decreased and was very low at 21 days after treatment (DAT); the levels of amino-3-hydroxy-5-methyl-4isoxazolepropionic acid (AMPA), which is the main metabolite of glyphosate, increased during this time (Figure 1)
For doses of 360 g a.e. ha−1 and below, the levels of glyphosate in the plants at 21 DAT were similar to those observed at 2 DAT, which may be related to slower glyphosate AMPA
Summary
Brazil is the world’s largest sugarcane (Saccharum spp.) producer, with a planted area of approximately 9.09 million hectares and a mean yield of 72.444 kg·ha−1 [1]. Sugarcane is a semi-perennial plant requiring a tropical or sub-tropical climate. The cultivation of sugarcane is one of the best alternatives for the sustainable production of large amounts of biomass that may be converted into various products, especially sugar and ethanol. The glyphosate mechanism of action is the enzymatic inhibition of EPSPS (5-enolpyruvylshikimate-3-phosphate (EPSP) synthase, E.C. 2.5.1. 19), which catalyzes the reaction of shikimate-3-phosphate (S3P) with phosphoenolpyruvate (PEP), forming 5-enolpyruvylshikimate-3-phosphate (EPSP) and inorganic phosphorus (Pi) [7]. The enzymatic inhibition of EPSPS by glyphosate affects the shikimic acid metabolic pathway, which generates the three aromatic amino acids phenylalanine, tyrosine, and tryptophan [8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
