Parthenium hysterophorus

Physical attributes This plant is described as an erect, annual herb with a branched, trichome covered stem that becomes woody with time. It has a deep taproot, and can grow from 1.5 to 2 meters in vertical height especially in good soil. The young plants begin by forming a basal rosette of pale green, dissected, lobed, alternate leaves that can get up to 30 centimeters in length. After stem elongation is initiated, the leaves gradually become smaller. The leaves are said to resemble carrot leaves. The flower heads are a creamy white color, and they protrude from the forks in the leaves. Each bud has about 5 to 8 florets. Life cycle Parthenium hysterophorus is known for being a fecund, but ephemeral herbaceous plant. They cannot germinate well if the seeds are not buried at least 5 centimeters below the surface of the soil. Temperature wise, germination can occur between , although the optimum temperature range is . Each flower has five black seeds. Each fruit is cypsela. P. hysterophorus reproduces through seeds, so how the seeds are distributed and when is very important. The dispersal of seeds can be mediated by several methods. These include: water currents, stock feed, animals, and occasionally the wind. When it comes to long distance distribution, which contributes heavily to its invasive abilities, P. hysterophorus is an allelopathic plant. Such plants produce growth-inhibiting chemicals that can positively or negatively affect the growth of other plants around them. Invasive species tend to have a negative allelopathic effect, causing the arrest of growth for the native plants. Pasture growth, fruit setting in crops, and forage production are all negatively affected by the allelopathic chemicals that the weed releases. Such allelopathic chemicals for P. hysterophorus include many phenolic acid derivatives and a sesquiterpene lactone called parthenin. While parthenin is amongst many chemicals released by P. hysterophorus to be pinned as the most responsible for plant growth inhibition, it is also a severe irritant and allergen. Exposure to the parthenin in the plant can cause contact dermatitis in both plants and animals. The Parthenium pollen grains frequently trigger pollen allergies. If ingested, it can cause respiratory illness side effects such as hay fever, asthma, burning and blisters, breathlessness, choking, and allergic rhinitis in humans. ==Invasive species==

Parthenium hysterophorus has been coined as one of the worst, and most successful invasive species on several continents. P. hysterophorus invades disturbed land, including roadsides. It infests pastures and farmland, causing often disastrous loss of yield, as reflected in common names such as famine weed. In some areas, heavy outbreaks have been ubiquitous, affecting livestock and crop production, and human health. Parthenium hysterophorus originally inhabited terrains around Mexico, Central and South America. This includes orchards, agricultural areas, wastelands, urban areas and more. They can also be found along the side of roads and railroad tracks. == Ecology ==

Depending on the habitat and the qualities of the organism, an invasive species can be detrimental and/or beneficial. While the plant is most known for its threat to ecosystems on multiple different continents, Parthenium hysterophorus has been found to have many attributes that could possibly benefit the ecosystems that it is technically non-native to. Threats Parthenium hysterophorus survives primarily through habitat degradation. It produces allelopathic chemicals that inhibit the growth of other plants, and are extremely competitive. They compete with local crops, pasture plants and other indigenous foliage for nitrogenous soil components. for its extremely destructive nature against agriculture and farming. P. hysterophorus was first recorded in the South African province, KwaZulu-Natal in 1880, but didn't become a true problem until the 1980s. P. hysterophorus slowly degrades the habitat over time by limiting the amount of healthy forage, so livestock productivity is jeopardized. This simultaneously damages the lives of the South African people who rely on agriculture and livestock, but also the environment as a whole. It is also a highly toxic allergen. It can cause respiratory and surface allergic reactions in humans and animals. The systematic ingestion of the weed by livestock poses a threat to food safety and security. Benefits The allelopathic chemicals that are released by Parthenium hysterophorus are most known for their harmful effects on plants and the ecosystem. Research shows that the same allelopathic properties can be advantageous to the ecosystem in various ways. P. hysterophorus is essentially a natural herbicide. Despite synthetic chemical herbicides being the go-to for killing weeds, they are toxic to the environment. They are also a threat to human and livestock health. Researchers have been searching for nature-derived alternatives to synthetic herbicides for decades. However, trying to lessen use of synthetic herbicides while still maintaining and increasing crop production poses a challenge. Herbicides made some natural resources like P. hysterophorus both more cost-effective and environmentally friendly. The weed is also reported to have pesticidal, insecticidal, nematocidal potential. Additionally, Parthenium hysterophorus is also being looked at as a potential energy source due to P. hysterophorus being a lignocellulosic biomass and a possible source of ethanol. Parthenium hysterophorus is also being investigated as a possible means of removing heavy metals and dyes from the environment, control of aquatic weeds, commercial enzyme production, an additive in manure for biogas production, as a biopesticide and as green manure and compost. ==Conservation and control==

According to the National Environmental Management Biodiversity Act (NEMBA), P. hysterophorus is classified as a Category 1b alien invader in South Africa. While physical control is labor-intensive and less practical for large-scale infestations, it remains a valuable tool when used in combination with chemical and cultural strategies. In Australia, the two species with the greatest effect seem to be the beetle Calligrapha bicolorata and a stem-galling moth Epiblema strenuana. However, other species that appear to have established usefully include a leaf-mining moth, Bucculatrix parthenica; a stem-galling weevil, Conotrachelus albocinereus; and a root-boring moth Carmenta ithacae. == References ==