Application of Germander (Teucrium polium) Plant Extracts as Natural Growth Promoters for Faba Bean under Sustainable Agriculture

Abstract

This study evaluated aqueous extracts of germander (Teucrium polium) as natural growth-promoting treatments for three faba bean varieties (Histal, Luz, and Holland) under laboratory and greenhouse conditions. Extracts were applied at 0.5%, 1.5%, and 3%, with untreated samples serving as controls. Germination, seedling growth, vegetative traits, root-nodule characteristics, chlorophyll content, and the phenolic profile of the extract were assessed. Responses varied according to extract concentration and variety, indicating a concentration-by-variety interaction. Under laboratory conditions, 1.5% generally produced the highest germination percentage, whereas 3% reduced germination in some treatments, suggesting concentration-dependent allelopathic effects. The Luz variety showed the strongest seedling response, recording plumule and radicle lengths of 8.050 and 16.540 cm, respectively, at 3%. In the greenhouse, the Holland variety performed favourably for several vegetative and nodulation traits, while extract treatments increased the number, activity, and weight of root nodules at selected concentrations. Chlorophyll responses also differed among varieties and concentrations. High-performance liquid chromatography identified apigenin, caffeic acid, epicatechin, ferulic acid, gallic acid, quercetin, and rutin. Gallic acid had the highest measured concentration at 142.6 ppm, whereas epicatechin had the lowest at 44.6 ppm. Overall, germander extracts showed potential as concentration-sensitive biostimulants for faba bean, although field validation is required before agronomic application.