Características fisiológicas e de crescimento em mudas de guaranazeiro (Paullinia cupana Kunth var. sorbilis (Mart.) Ducke) à doses de glifosato

Abstract

The guarana tree (Paullinia cupana Kunth var. sorbilis (Mart.) Ducke) is a crop known for its energetic properties from the caffeine found in its seeds. Despite the progress in the genetic improvement of the species, there is still demand regarding cultural treatments, for example weed management. Currently, this management is carried out through weeding or mowing, but in the presence of large infestations, herbicides are used. However, the effects that the drift of these products causes on the crop are unknown. In this sense, the objective was to investigate the effect of different doses of the herbicide glyphosate on guarana. In the first application, the seedlings were submitted to doses of 0, 126, 252, 540, 1,080, 2,160 and 3,240 g ae. ha-1 plus adhesive spreader (EA) at a concentration of 0.5% and in the second application at doses of 0, 126, 252, 540, 1,080 g ae. ha-1 and EA, evaluated for 60 days in each application. Samples related to seedling biometry, gas exchange, occurrence of anthracnose and phytotoxicity were performed and levels of photosynthetic pigments and proline were quantified. The doses 2160 and 3240 g ae. ha-1 altered the development of seedlings, leading them to death. There were no significant changes in the gas exchange of guarana tree seedlings submitted to glyphosate doses. There was the occurrence and gradual increase of anthracnose in seedlings submitted to glyphosate doses. The lowest doses of glyphosate (126, 252, 540 g ae. ha-1) caused leaf depigmentation and overbudding. Higher doses caused the death of the tips and yellowing of all the leaves. There was no significant difference in photosynthetic pigments and proline concentration. Low doses of the herbicide glyphosate did not interfere in the development of guarana tree seedlings (cultivar BRS-Maués). Based on the results, it is recommended to use glyphosate in a directed manner, in an area of guarana tree cultivation, as part of the integrated management of weeds, without prejudice to the development of the culture.