Hormetic effects of glyphosate on niger (guizotia abyssinica): field insights into growth, physiology, and yield responses

A field experiment conducted in 2023 evaluated the physiological effects of varying glyphosate concentrations (0,1.5, 3, 6, 12, 25, 50,100, 200 and 400 g a.i. ha-1) on the growth and development of niger (Guizotia abyssinica Cass). A hormetic response was observed at 6 g a.i. ha⁻¹, where the grain yield increased by 33% compared to the control, along with enhanced branching and inflorescence production. This dosage also corresponded with elevated catalase (CAT) activity and reduced levels of hydrogen peroxide (H₂O₂) and proline. Maximal activities of ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) were observed at 50 and 100 g a.i. ha⁻¹, respectively. Glyphosate concentrations of 6 g a.i. ha⁻¹ and below induced less than 10% chlorosis, from which the plants fully recovered. In contrast, applications of 6, 12, 25, and 50 g a.i. ha⁻¹ resulted in reductions in plant dry matter by 34%, 48%, 46%, and 50%, respectively. Higher doses ranging from 100 to 400 g a.i. ha⁻¹ caused severe phytotoxicity (>80%) and ultimately led to plant death. The results of this experiment suggest that a very low glyphosate dosage of 6 g a.i. ha⁻¹ may affect physiological processes in niger plants, potentially contributing to increased grain production. However, such responses to low-dose herbicide application are known to be highly variable and influenced by factors such as environmental conditions, plant development, and species-specific sensitivity. Further investigation is required to clarify the underlying mechanisms and to determine the consistency and practical significance of these effects under field conditions.

Citation

Ghafori, A., Zahedi, M., Karimmojeni, H. and Baldwin, T.C. (2025) Hormetic effects of glyphosate on niger (guizotia abyssinica): field insights into growth, physiology, and yield responses. Environmental Science and Pollution Research. 32, pp. 22625–22635 https://doi.org/10.1007/s11356-025-36945-9

Type

Journal article

Language

en

Description

This is an author's accepted manuscript of an article published by Springer Nature in Environmental Science and Pollution Research on 26 September 2025, available online: https://doi.org/10.1007/s11356-025-36945-9. The accepted manuscript may differ from the final published version. For re-use please see Springer's terms and conditions.

ISSN

0944-1344

EISSN

1614-7499

Collections

Faculty of Science and Engineering