Allelopathic effect of Mintweed [Hyptis suaveolens (L.) Poit.] green and brown leaves aqueous extract on seed germination and seedling growth of cowpea.

Abstract

Hyptis suaveolens is an invasive weed that has negative effects on native plant communities and impedes the growth of vulnerable or threatened species growing near it. This study revealed the allelopathic effect of the aqueous extract of the green and brown leaves of Hyptis suaveolens on seed germination and seedling growth of cowpea at different concentration (0 %, 2.5 %, 5 %, 7.5 % and 10 %) in a laboratory – based experiment. The treatments were arranged as a 2 x 5 factorial in a Completely Randomized Design (CRD) in four replications. Results revealed that irrespective of the leaf type, there was no significant difference in the allelopathic potential on the seed germination and seedling growth of cowpea. In contrast, the concentration of the extracts had a significant allelopathic effect on cowpea seed germination and seedling growth, such that the inhibition was concentration dependent. The inhibition of the seed germination and seedling growth increased with the increase in the concentration from 0 to 10 %. The highest concentration (10%) of H. suaveolens leaf extract significantly reduced the germination percentage, germination index, mean germination time, radicle and plumule lengths by 61.5 %, 63.9 %, 61.7 %, 54.2 % and 62.5 %, respectively. It was apparent that the 10% concentration had more inhibitory (-61.5%) effect on the germination and seedling growth of cowpea relative to the control. This weed must therefore be controlled in the cowpea field at their initial growth.