Allelopathic potential of the alien invader weed Campuloclinium macrocephalum (Less)D.C.

Abstract

It has been suggested that the Category 1 weed, Campuloclinium macrocephalum (Less) D.C has allelopathic potential, which would, at least partially, explain its apparent success as an alien plant in South Africa. Studies were done on the plant’s root, stems and leaves to determine where the strongest allelopathic potential can be found. Once it was determined that the leaves held the strongest potential, bioassay studies were conducted on lettuce (Lactuca sativa), Eragrostis tef, Eragrostis curvula and Panicum maximum with positive results found for C. macrocephalum’s allelopathic potential. Electron microscopy was performed to determine whether allelopathic substances originate and/or are stored on the surfaces of the leaf. Positive results proved that there are possible sources of allelochemicals on both adaxial and abaxial surfaces of young and mature leaves. A dipping experiment involving dichloromethane then followed to determine the solubility of the contents of the glands found on the leaf surfaces. It can be deduced from results of all of the experiments performed that C. macrocephalum is potentially allelopathic to dicotyledonous species and to grasses. Structures found on the leaves of the plant could possibly contain the allelochemicals used by the plant to ensure its successful invasive growth habits in South Africa. The allelopathic effects that this weed will have on desirable species should be considered within the broader context of its ability to interfere with those species. In this regard its competitive ability should also be studied. Campuloclinium macrocephalum is fast invading susceptible areas of South Africa; if continuous research on control and eradication of this plant is not carried out soon, the country could suffer grave economic losses. Copyright