RÉSUMÉ
Parthenium hysterophorus is a prime noxious weed across the world and resorting its nativity weed to Tropical North and South America which has invaded more than 50 countries throughout the world. It was accidentally introduced in India with food-grains imported from Mexico. Parthenium plant contains chemicals, like parthenin, hysterin, hymenin, and ambrosin, and due to the presence of these chemicals, the weed exerts strong allelopathic effects on different crops. Parthenin has been reported as a germination inhibitor as well as radical growth inhibitor in a variety of dicot and monocot plants. Because of its strong competitiveness for soil moisture, space and nutrients with crops and its allergenic properties, it poses serious threat to cereal crops and livestock. Parthenium is difficult to control because of its wider adaptation to diverse climatic conditions. The aim of this research article is to explore effect of environmental factors on germination, shoot and root length of Parthenium hysterophorus. The effect of light periods, temperature, pH, osmotic potential and salt stress on germination, shoot and root length of parthenium was studied and found that maximum germination at 16 h (57%), 25°C (81%), pH 7 (98%), 0 MPa (85%) and 0 mM NaCl (84%), respectively and same trend was followed in shoot and root length. Therefore, the understanding of growth behavior of parthenium will help in formulating better management practices for the same.