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.

Ecological Traits and Socio-Economic Impacts of the Alien Invader Weed Parthenium hysterophorus L. in South Africa’s Rangeland Ecosystems: A Review

“…Parthenium has been termed the worst invasive alien plant species, and it is considered a cropping, grazing, and environmental weed [67]. It can outcompete annual crops, causing tremendous yield loss and suppressing the growth of surrounding native species.…”

“…The success of aggressive plant species such as Parthenium concerning invasion and establishment in new areas is thought to involve their ability to suppress and replace other species within the existing plant community [71]. Phenolics and sesquiterpene lactones are two major classes of allelopathic compounds produced by Parthenium, and these chemicals are known to have a significant adverse effect on the germination, seedling emergence, and growth of various plant species [67]. The allelopathic properties of different parts of this weed have been well demonstrated in the germination and seedling growth of surrounding plant species.…”

“…Furthermore, Netsere and Mendesil [73] reported that the aqueous extracts of the shoot, leaf, flower, and root of Parthenium hysterophorus inhibited the germination of crops (Glycine max L. and Phaseolus vulgaris L.). Under natural conditions, Putri [67] examined the allelopathic effect of Parthenium leaf litter and reported that wheat growth reduction (Triticum aestivum L.) increased as the amount of Parthenium leaf litter increased. Similarly, Khosla and Sobti [74] reported that Parthenium caused a yield decrease of 40% in crops and up to a 90% reduction in forage production in grasslands in India.…”

“…Parthenium hysterophorus is of great concern among the invasive alien plant species identified in South Africa. It is considered one of the worst weeds responsible for causing several ecological and agricultural problems, such as the loss of crop productivity, fodder scarcity, health problems for human beings and livestock, and biodiversity depletion [66,67,76]. Parthenium is progressively spreading in the country and covering vast areas in KwaZulu-Natal and Mpumalanga, as well as the North-West, Limpopo, and Gauteng Provinces (Figure 3), resulting in a negative impact on crop production, native biodiversity, livestock feed supply, and the health of the local people.…”