Effect of the aqueous extract of the germander plant (Teucrium polium) on the morphological and anatomical characteristics of the root nodules of faba bean varieties (Vicia faba L.)

Abstract

This study aimed to evaluate the effect of the aqueous extract of Teucrium polium on the morphological and anatomical characteristics of root nodules in three cultivars of faba bean (Vicia faba L.), in the context of sustainable agriculture and the development of natural alternatives to chemical fertilizers. A greenhouse experiment was conducted using three concentrations of the plant extract (0.5%, 1.5%, and 3%), applied during different growth stages. The results revealed that the aqueous extract significantly improved root nodule traits in all studied cultivars, including nodule number, number of effective nodules, and nodule weight, without altering their general shape. The 1.5% concentration showed the greatest effectiveness, achieving superior values for most measured parameters. Among the cultivars, Luz exhibited the best performance, indicating the influence of genetic variation on the symbiotic efficiency with Rhizobium bacteria. Anatomical analysis showed that the moderate concentration (1.5%) enhanced nodule diameter, length, and the size of the infected zone, which is closely associated with nitrogen fixation efficiency. In contrast, the higher concentration (3%) showed a slight inhibitory effect on some traits. These findings suggest that Teucrium polium extract, particularly at moderate concentrations, can serve as an effective natural biostimulant to enhance nodulation and biological nitrogen fixation in faba bean. This approach may contribute to improving soil fertility, reducing dependence on chemical fertilizers, and supporting environmentally sustainable agricultural practices.