Deriva simulada de glifosato em plantas adultas de guaranazeiro e dinâmica da produção de frutos, metilxantinas e polifenóis

Abstract

The Guarana plant (Paullinia cupana Kunth) is a plant with high caffeine content and antioxidant compounds such as catechin and epicatechin. Due to the economic importance of guarana to the State of Amazonas studies has sought to increase productivity. Weed control is one of the most laborious and most productive management practices, with the adoption of herbicides as a viable alternative, however the herbicide application drift can cause damage to the crop of interest. The objective of this work was to evaluate the physiological and fruit production responses of guarana adult plants after being exposed to different concentrations of simulated glyphosate drift (equivalent to 57.6, 115.2, 230.4, 460.8 g a.e. ha-1). Seven days after application of the treatments, foliar evaluations were performed on pigment content, chlorophyll fluorescence, SPAD index, malondialdehyde content, proteins, total phenolic compounds, amino acids, polyphenols and methylxanthines in the leaves. We also evaluated the differential effects of glyphosate on fruit production and secondary compounds of economic interest in this crop. Glyphosate causes slight effects on the physiology of adult plants, but they are reversible and do not cause changes in the production and content of important metabolites. It can be considered as an alternative for the control of weeds without causing damage to this species. In addition, the amount of mature fruits harvested per plant and five harvest times were determined over two months of the stepwise production of the commercially important metabolites (caffeine, theobromine, theophylline, catechin and epicatechin) to obtain better utilization of these compounds during the harvest and it has been observed that they may increase or decrease throughout the harvest period. The amount of fruits harvested tends to increase at the end of the harvest, becoming more homogeneous and less frequent and the secondary metabolites do not accompany the production of fruits.