Hormetic Effect of Glyphosate on the Morphology, Physiology and Metabolism of Coffee Plants

Abstract

Glyphosate is a nonselective herbicide of systemic action that inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, thus compromising amino acid production and consequently the growth and development of susceptible plants. The objective of this study was to evaluate the hormetic effect of glyphosate on the morphology, physiology, and biochemistry of coffee plants. Coffee seedlings (Coffea arabica cv Catuaí Vermelho IAC-144) were transplanted into pots filled with a mixture of soil and substrate and subjected to ten doses of glyphosate: 0, 11.25, 22.5, 45, 90, 180, 360, 720, 1440, and 2880 g acid equivalent (ae) ha−1. Evaluations were performed using the morphological, physiological, and biochemical variables. Data analysis for the confirmation of hormesis occurred with the application of mathematical models. The hormetic effect of glyphosate on coffee plant morphology was determined by the variables plant height, number of leaves, leaf area, and leaf, stem, and total dry mass. Doses from 14.5 to 30 g ae ha−1 caused the highest stimulation. In the physiological analyses, the highest stimulation was observed upon CO2 assimilation, transpiration, stomatal conductance, carboxylation efficiency, intrinsic water use efficiency, electron transport rate, and photochemical efficiency of photosystem II at doses ranging from 4.4 to 55 g ae ha−1. The biochemical analyses revealed significant increases in the concentrations of quinic acid, salicylic acid, caffeic acid, and coumaric acid, with maximum stimulation at doses between 3 and 140 g ae ha−1. Thus, the application of low doses of glyphosate has positive effects on the morphology, physiology, and biochemistry of coffee plants.

Hormetic Effect Caused by Sublethal Doses of Glyphosate on Toona ciliata M. Roem

“…This explains the effects we observed when exposing T. ciliata plants to doses of 9.6 and 19.2 g ha −1 of glyphosate, which induced a better photochemical performance index and less energy dissipation in the form of heat, which indicates a reduction in stress caused by the incidence luminous. Similarly, Costa et al [ 66 ] showed that glyphosate applied between doses of 4.4 to 55 g ha −1 in Coffea arabica plants improves the photochemical efficiency of PSII.…”

“…The reduction in A in plants grown under a sublethal dose of 76.8 g ha −1 resulted in lower rates of production or transport of assimilated photosynthates and, consequently, reduced height. According to Costa et al [ 66 ], these alterations are responsible for growth decline. However, a dose of 76.4 g ha −1 induced stem thickening, similar to the dose used by Marques et al [ 68 ], who applied 60 g ha −1 to Cedrela odorata , a species of the same family (Meliaceae), also known as cedar.…”

Glyphosate hormesis stimulates tomato (Solanum lycopersicum L.) plant growth and enhances tolerance against environmental abiotic stress by triggering nonphotochemical quenching

“…19 In addition to herbicidal applications, low doses of glyphosate that stimulate plant growth have become a considerable research topic. [20][21][22][23][24] Low glyphosate doses can increase photosynthetic pigments content and stimulate photosynthesis, 25,26 yet the specific mechanisms, especially the function of PSII in hormesis, remain unclear. 15,27 In this study, we mainly focus on the biphasic relationship between glyphosate dose and tomato (Solanum lycopersicum L.) plant growth, and aim to evaluate the potential of hormesis to enhance plant tolerance against stress caused by diuron (DCMU), a presentative photosynthesis inhibitor.…”

“…In addition to herbicidal applications, low doses of glyphosate that stimulate plant growth have become a considerable research topic 20–24 . Low glyphosate doses can increase photosynthetic pigments content and stimulate photosynthesis, 25,26 yet the specific mechanisms, especially the function of PSII in hormesis, remain unclear 15,27 …”