Sugarcane's chemical ripeners: Effects on growth and gas exchange of Citharexylum myrianthum, a Brazilian native tree species

Abstract

Chemical ripeners are being used to anticipate the ripening process of sugarcane. These products act in specific enzyme or protein systems of plants, altering their functionality. However, these products can seriously affect the development of non-target species. In light of the proximity of permanent preservation areas to sugarcane plantations, we aimed at understanding the effect of simulated drift of chemical ripeners on 18-month age seedlings of Citharexylum myrianthum, a Brazilian native tree species. The experiment was conducted under semi-controlled conditions using a randomized block design with six replications. Treatments consisted of a 6x2 factorial arrangement, corresponding to six concentrations of glyphosate and sulfometuron-methyl, equivalent to 0, 5, 15, 30, 45, and 60% of commercial dose recommended for sugarcane. Plant height, stem diameter, number of leaves, total chlorophyll content, chlorophyll a fluorescence, and gas exchange were measured at 7, 30, and 60 days after application (DAA),. The leaf area and dry mass of plants were also measured at the end of the experimental period (60 DAA),. Both ripeners caused visual symptoms of phytointoxication in C. myrianthum, which were accompanied by alterations in gas exchange until 30 DAA. At 60 DAA, all plants treated with glyphosate recovered their photosynthetic capacity, without detrimental effect on their initial development, while those treated with 60% of sulfometuron-methyl showed limited growth in height coupled to super sprout due to the death of apical meristem. Despite no significant difference in total dry mass, the development of these plants was affected.