Hormetic effects of reduced concentrations of glyphosate on germination and seedling characteristics of cotton

Background and Objectives: Hormesis refers to the beneficial response to exposure to low levels of chemicals under otherwise adverse conditions. Certain herbicides can stimulate growth at reduced concentrations, making them promising agents for inducing hormesis. However, research on herbicide-induced stimulatory effects on germination indices is limited. This study aims to evaluate the impact of different glyphosate concentrations on the germination and seedling characteristics of cotton.
 Materials and Methods: To assess the effect of glyphosate on cotton germination and seedling development, two experiments were conducted in 2024. These experiments explored the hormetic effects of glyphosate by incorporating it into the growth medium and by seed priming with various glyphosate concentrations. Both experiments were designed as randomised complete block designs with three replications. Glyphosate was applied at six concentrations: 10, 20, 40, 80, 160, and 320 ppm, alongside a control. The traits measured included seedling length, fresh and dry weight, germination percentage, seed germination index, phytotoxicity percentage, tolerance index, and germination speed.
 
Results: The results indicated that the 10 ppm glyphosate treatment elicited hormetic effects on several traits. In the growth medium experiment, this treatment increased seedling length by 83% compared to the control. Similarly, in the seed priming experiment, seedling length was enhanced by 164% with the same concentration. The 10 ppm treatment also resulted in a 60% increase in fresh weight and a 120% increase in dry weight in the growth medium experiment, while in the seed priming experiment, fresh weight increased by 250% and dry weight by 315% compared to the control. Additionally, the 10 ppm treatment improved seed germination by 77% in the growth medium test and by approximately 89% in the seed priming test. Conversely, the 40 and 320 ppm treatments were associated with the most pronounced inhibitory effects on seedling length, fresh weight, dry weight, and germination in both experiments.
 Conclusion: The 10 ppm glyphosate treatment demonstrated the most favourable impact on the studied traits. These findings suggest that non-toxic concentrations of glyphosate can enhance seedling establishment and improve competitive ability against weeds through hormesis.