Allelopathic effect of parthenium weed (Parthenium hysterophorus L.) leaf litter on the seedling emergence and growth of wheat (Triticum aestivum L.)

Abstract

Parthenium weed (Parthenium hysterophorus L) is a pantropical weed from Central America that has invaded more than 40 countries in the world. The invasiveness and competitive advantage of this weed are attributed to its ability to produce large number of seeds, tolerance to environmental stresses, climate change adaptability, and allelopathic properties. Phenolics and sesquiterpene lactones are two major classes of allelopathic compound produced by parthenium weed and these chemicals are known to have significant negative effect on germination, seedling emergence and growth of various plants species. The allelopathic properties of parthenium weed had been investigated in various past studies, however, most of the studies conducted the experiment under laboratory conditions with the allelopathic effect being tested by applying the aqueous extract of the weed directly on the test plants. This study aimed to examine the allelopathic effect of the leaf litter of parthenium weed under more natural conditions. Fresh leaves were oven dried and crushed to crude powder, hereafter referred to as leaf litter. The leaf litter were incorporated into the upper layer of the media of Greenfingers compost bark in pots. In to this were sown the seeds of the test plans then set to germinate. Another treatment without leaf litter was set up as a series of control. The treatments were arranged in simple randomized design in the glasshouse. After one week, any seedling produced were counted and thinned to five seedlings per pot. The plants produced from these seedlings were harvested after further 40 days of growth and the growth parameter including root length, shoot length, and dry weight were measured. The measurable growth reduction increased as the amount of parthenium weed leaf litter increased but variability between results existed. The uncontrollable factors and seasonal conditions may cause this variability, in addition to the seed quality. The chemicals contained within the parthenium weed leaf litter has been shown to affect crop growth presumably through allelopathic activity under natural field conditions.