Modeling approach of allelopathy effect of Urospermum dalechampii and Andryala integrifolia on lettuce-seed germination and seedling growth

Spontaneous plant interactions in their environment would acts by allelochemicals produced by secondary metabolism pathway. This study aimed to evaluate the allelopathic effect of four aqueous extracts from the aerial and root parts of Urospermum dalechampii L. and Andryala integrifolia L., growing in sympatry in the same locality, on seed germination and seedling growth of lettuce (Lactuca sativa L.). The effect of extracts at different concentrations and combinations was conducted using secondary polynomial model based on the Box–Behnken plan generating 27 germination assays and one control assay. Extracts of the two species were subjected to qualitative and quantitative analyses including total polyphenols and flavonoids contents, antioxidant activity and liquid chromatography-mass spectrometry (LC–MS). Results showed that the germination percentage of the control assay reached 100% after 7 days. However, important inhibitions were found in the 27 assays with significant variation between them. In addition, the mathematical model of germination percentage was determined as secondary polynomial equation including only extracts and their interactions having significant reduction on lettuce-seed germination. The phytochemical screening of different aqueous extracts allowed the detection of 17 phenolic compounds that contributed to the observed inhibition. Results of the combined effects of aerial (5%) and root (5%) parts extracts from each plant exhibited the complete inhibition of seed germination. These results provide valuable information on the possible use of these species as an economical and eco-friendly bioherbicide to promote sustainable weed management.