Assessment of Allelopathic Effects of an aqueous leaf extract of Tecoma stans (L.) Juss. ex Kunth, on seed germination and seedling growth of Allium cepa L. and Portulacca oleraceae L.

Abstract

With the noticeable increase in the cultivation of the Tecoma stans shrub as an ornamental plants on most streets in Libyan cities, and in the context of assessing its environmental impacts as well as the search for safe alternatives to chemical herbicides, the aim of this study is to evaluate the allelopathic effect of the aqueous extract of Tecoma leaves on the germination and early growth of Allium cepa L. and Portulaca oleracea L., as well as to perform qualitative detection of certain chemical compounds with allelopathic activity in the leaves of T. stans. The results of the present study indicated that, the extract of T. stans  contains higher levels of phenols and moderate levels of alkaloids, followed by lower levels of flavonoids, saponins, and glycosides. The results of the efficacy test for four different concentrations of the aqueous extract of Tecoma leaves  ( 10,20,30,40 g/L). The highest inhibition rates were recorded in A. cepa., compared to P. oleracea., and the highest inhibition rate was observed in average root length (76.22%) at a concentration of 40 g/L. The inhibitory activity of the increased proportionally with increasing concentration of the plant extract; this is attributed to the plant extract’s content  of biologically active compounds such as flavonoids, alkaloids, and saponins