Hormetic effect of glyphosate persists during the entire growth period and increases sugarcane yield

Abstract

BACKGROUND: Stimulation of plant growth by low doses of a toxic compound is defined as a hormetic effect. Exposure of plants to low doses of glyphosate can cause stimulatory effects on growth or other variables. Sugarcane is the major biofuel and sugarproduction crop cultivated in Brazil, but its expansion to new areas is limited; therefore, there is a demand for new technologies to improve sugarcane production per unit area. The use of pesticides to stimulate growth through the hormetic effect might be a suitable strategy to increase sugarcane yields. The purpose of this research was to investigate the effect of a low dose of glyphosate on metabolic compound accumulation, leaf phosphorus (P) concentration, and morphological variables across a one-year sugarcane cycle, as well as to determine whether the glyphosate effect was sustained and effective in improving the yield and technological quality of the sugarcane at harvest. RESULTS:The application of a low dose of glyphosate led to higher concentrations of shikimic acid and quinic acid, higher leaf P concentrations, and improved plant growth, yield, and technological quality of the sugarcane, by increasing the Brix% juice, pol% cane, total recoverable sugar, tons of culms per hectare, and tons of pol per hectare, relative to the results for an untreated control.CONCLUSIONS: The increased growth stimuli, observed through several variables, promoted an improvement in sugarcane yield. Therefore, the application of a low dose of glyphosate to sugarcane is a promising practice for crop management.

Glyphosate hormesis mitigates the effect of water deficit in safflower (Carthamus tinctorius L.)

“…1,2 It acts by inhibiting the enzyme 5-enolpyruvylchiquime-3-phosphate synthase (EPSPS) of the shikimate pathway, 1,3 preventing the biosynthesis of essential aromatic amino acids required for protein synthesis, indole acetic acid (IAA) and plastoquinone, and secondary compounds needed for defense against pathogens. [4][5][6] The stimulatory effect of treatment with low doses of chemicals on the growth of various plant species has been the focus of several studies. [5][6][7][8][9][10][11][12][13][14] In this context, the term hormesis refers to an adaptive/protective response caused by chemical stressors when used in low doses in plants.…”

“…[4][5][6] The stimulatory effect of treatment with low doses of chemicals on the growth of various plant species has been the focus of several studies. [5][6][7][8][9][10][11][12][13][14] In this context, the term hormesis refers to an adaptive/protective response caused by chemical stressors when used in low doses in plants. 15 The most widely used herbicide in the world, glyphosate, causes hormesis, 1,3,9,16,17 and studies are ongoing to elucidate the ability of low doses of glyphosate to stimulate plant growth 13 and improve agricultural sustainability by reducing environmental impacts.…”

“…20,21 When applied during the initial stage of plant development, low doses of glyphosate lead to an increase in biomass, photosynthetic activity, protein content and amino acids and consequently, greater resistance to pests. 6,9,11,22 The stimulus dose varies for each species according to the plant's sensitivity to glyphosate, requiring individual studies to determine the dose. In addition to its commercial value, safflower (Carthamus tinctorius L.) can be cultivated in regions with little available water and low production costs, and is therefore an alternative crop for growing during the dry season in Brazil.…”

“…Although our research group has provided information on the stimulating effect of low doses of glyphosate on Commelia benghalensis, Eucalyptus grandis, maize, Pinus caribea, soybean, 5 sugarcane, [6][7][8] Urochloa decumbens, 9,13 sugarcane, eucalyptus, 11 and Phaseolus vulgaris, 14 deeper knowledge of glyphosate-caused hormesis on C. tinctorius under water deficiency conditions is needed, because water deficit is the most unpredictable abiotic stress in terms of occurrence, severity, distribution and duration. 30 Studies on the interaction between water deficit and glyphosate hormesis in plants are rare; however, previous studies with Phaseolus vulgaris have shown a greater tolerance to water stress in the presence of low doses of glyphosate.…”

“…Glyphosate ( N ‐(phosphonomethyl)glycine) is a slow‐acting, systemic, non‐selective, post‐emergence herbicide 1,2 . It acts by inhibiting the enzyme 5‐enolpyruvylchiquime‐3‐phosphate synthase (EPSPS) of the shikimate pathway, 1,3 preventing the biosynthesis of essential aromatic amino acids required for protein synthesis, indole acetic acid (IAA) and plastoquinone, and secondary compounds needed for defense against pathogens 4‐6 …”