Phytotoxic Effects of Xanthotoxin on Germination and Seedling Growth of Trifolium and Medicago sativa (Alfalfa)

Abstract

Allelopathy, the chemical interaction between plants that influences the growth and development of neighboring species, has emerged as a promising strategy for sustainable weed management. Xanthotoxin (8‑methoxypsoralen), a furanocoumarin belonging to the phenylpropanoid group, is naturally present in Rutaceae and Apiaceae plants such as bergamot and wild carrot. While traditionally applied in medicine, its allelopathic potential as a bioherbicide remains underexplored. This study investigated the phytotoxic effects of xanthotoxin on two agriculturally important fodder plants, Trifolium (clover) and Medicago sativa (alfalfa). Seeds were sterilized and exposed to xanthotoxin solutions at concentrations of 0.001, 0.01, 0.1, and 1 mg/ml, with distilled water plus Tween 20 serving as the control. Germination rates were recorded daily for six days, and seedling growth was assessed by measuring root and shoot lengths. Statistical analysis was performed using SPSS v21 and Zanken’s test. Results revealed a clear dose-dependent inhibition of germination and seedling development. Even at the lowest concentration, xanthotoxin reduced germination compared to the control, while complete suppression of both root and shoot growth occurred at 1 mg/ml. These findings confirm the strong phytotoxicity of xanthotoxin and highlight its potential as a natural herbicide. Compared to synthetic herbicides, allelochemicals such as xanthotoxin offer advantages including biodegradability, reduced environmental toxicity, and alignment with sustainable agricultural practices. Further research is needed to evaluate its selectivity, ecological safety, and field-level applicability, but this study provides foundational evidence supporting xanthotoxin’s role in environmentally friendly weed management.