Plant diversity threats by Parthenium hysterophorus. Dr. Arpana Mishra Mahatma Gandhi Chitrakoot Gramodaya Vishwavidyalaya Chitrakoot, Satna (M.P)

1- Introduction Parthenium hysterophorus is a problematic weed to human and floral diversity. It is also known as congress weed, carrot grass, white head etc. It is member of Asteraceae family. Parthenium is a weed of national significance . It is a native of West Indies and Central America. It is an exotic weed and was accidentally introduced in India along with food grain under PL 480 scheme. Parthenium hysterophorus was reported for the first time in India in 1956. Parthenium hysterophorus is a world wide weed. It has been distributed to many countries in Africa, Asia and the pacific and has become a major weed in India and Australia. It is commonly spread road sides, waste lands, marshy lands and fertile lands.

2- World-wide distribution of Parthenium.

3- DISTRIBUTION OF PARTHENIUM IN INDIA

4- SPREAD OF PARTHENIUM

5- Parthenium & health problems: Parthenium is a allergic plant and pollen can cause allergic reactions such as 1- Respiratory problems such as hayfever or asthma (allergic bronchitis). 2- Weight loss. 3- Swelling. 4- Puffy eyes. 5- Contact dermatitis- (a) Skin rashes

(b) Peeling skin -

(c) Red,irritated weepy skin on hand & face -

Harmful affects on crop production and Biodiversity - Parthenium weed is a serious problem to farmers. Parthenium produce several allelochemicals such as parthenin and other phenolic acid – caffeic acid, vanillic acid, ansic acid, chlorogenic acid and parahydroxy benzoic acid that have inhibit the germination and growth of other plants. This toxic weed have become a serious threat to plant biodiversity in many parts of the world. Parthenium reduce yield and quality of crop production system . Its allelopathic properties has the potential to disrupt natural ecosystems. The allelochemicals released from Parthenium inhibit the growth of pasture grasses, several crops ( Oryza sativa, Helianthus annus, Glycine max, Gossypium sps.), plants ( Acacia nilotica, Eucalyptus dives) and neighboring wild species ( Naja germinea, Ageratum conyzoides, Avena fatua and Bidens pilosa).

The term allelopathy was introduced by Molisch in 1937 and is derived from two Greek words Allelon means each other and Pathos means to suffer, the injurious effects of one upon another. However, the term is today generally accepted to cover both inhibitory and stimulatory (biochemical interaction) effects of one plant on another plant. Rice (1984) and Putnam (1985) reported that allelochemicals are present in virtually all plant tissue, i.e. leaves, fruit, stems, and roots. These allelochemicals are released by such processes as volatilization, root exudation, leaching and decomposition of plant residues. Leaves may be the most consistent source there are four ways in which the chemicals are released: Volatilization - release into the atmosphere. It is only significant under arid or semi-arid conditions. The compounds may be absorbed in vapour by surrounding plants, be absorbed from condensate in dew or may reach the soil and be taken up by the roots. Leaching - rainfall, dew or irrigation may leach the chemicals from the aerial parts of plants that are subsequently deposited on other plants or on the soil. Leaching may also occur through plant residues. Their solubility will affect their mobility in soil water. Root exudation - from plant roots into the soil environment. Whether these compounds are actively exuded, leaked or arise from dead cells sloughing off the roots is not clearly understood at this time. Decomposition of plant residues - it is difficult to determine whether toxic substances are contained in residues and simply released upon decomposition, or produced instead by micro-organisms utilizing the residues.

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