Physiological responses of citrus plants to glyphosate

Abstract

Currently, it is observed that the control of weeds for citrus is more expensive, as it is a perennial crop where weeds coexist at the same time and space, thus reducing control options, including the chemical. Allied to this, there are reports of the excessive and inadequate use of the herbicide glyphosate by Brazilian citrus growers, with four or more applications per agricultural year, many in sequence and/or in dosages above 2 kg of acid equivalent ha-1, being justified by themselves producers for the current low level of control. There is much speculation about the biochemical and physiological consequences of the interaction between citrus and glyphosate, and the existing works are still incipient and are not conclusive. Therefore, the objective of this project is to evaluate the implications of the use of glyphosate, elucidating everything from the disturbances in the metabolic route of the shikimic acid to the identification of the main intoxication pathways between this herbicide and the citrus plants. To this end, the project will be divided into two experiments: (I) "Chiquimate accumulation and amino acid concentrations in Pêra sweet orange plants under simulated glyphosate drift", which will evaluate different doses of glyphosate, determining the concentration of the chiquimate and the phenylalanine amino acids , tyrosine and tryptophan, in addition to analyzing photosynthesis, the accumulation of biomass, the growth of the aerial part, the root system and its morphological parameters; and, (II) "Development of citrus plants under directed application of glyphosate on leaves, soil and on weeds", which will evaluate two types of soil, different application sites and doses of glyphosate in Pêra sweet orange plants, determining the concentration of chiquimate, in addition to analyzing the accumulation of biomass, the growth of the aerial part, the root system and its morphological parameters. Thus, the results of this project will contribute to the confirmation of the possible implications of glyphosate, providing information for a more sustainable management of weeds in citrus, which can bring benefits to the entire citrus chain due to the greater health of the orchards.