Efeitos da deriva simulada do glyphosate na fisiologia e produção da batata-doce (cv. Duda)

Abstract

The sweet potato (Ipomoea batatas L. (Lam.)) is a tropical plant of American origin, and is therefore well adapted to the climatic conditions of Brazil. Among the amylaceous crops, sweet potatoes have been the subject of research for more than a decade by researchers from the Federal University of Tocantins (UFT). From the various existing conditions that can affect the sweet potato cycle, interfering in the formation and filling of its tuberous roots can be mentioned biotic and abiotic factors. Thus, genetic, nutritional, climatic or chemical problems (herbicide toxicity) should be considered as physiological disorders. Considerable damage can be caused by improper or accidental application of a wide range of agricultural chemicals (herbicides). The occurrence of accidental drift is considered a serious problem in many growing areas, especially when non-selective herbicides such as glyphosate are used. Thus, the objective of this study was to evaluate the effects of simulated glyphosate drift on the physiology and production of sweet potato (cv. Duda). The experiment was conducted at the Federal University of Tocantins, campus Gurupi. The design was 3 x 3 + 1, corresponding to 3 application times (25, 50 and 75 days after transplanting) x 3 doses of glyphosate (72, 144 and 288 g e.a. L-1), plus one control without application (0 g e.a. L-1). The experiment was distributed in randomized blocks, repeated four times. Physiological analyzes (at two-day intervals for a period of ten days after application of the herbicide) were performed using IRGA equipment, evaluating the variables: stomatal conductance, internal carbon, CO2 net assimilation, transpiration, instant water use efficiency and instantaneous efficiency of carboxylation, morphological (fresh shoot mass, shoot dry matter, fresh root mass and root dry mass) at the end of the experiment, root starch and the amount of ethanol was estimated. The glyphosate doses of 144 and 288 g e.a. L-1 were the ones that most reduced the physiological and morphological variables evaluated. However at the 144 g e.a. L-1 dose of glyphosate, the percentage of starch and the ethanol estimate was higher than the control. The periods that most affected the morphological variables of sweet potato were in the applications at 50 and 75 days after planting.