Allelopathic Effect of Amaranthus spinosus on Parthenium hysterophorus

The allelopathic influence of Amaranthus spinosus on Parthenium hysterophorus were evaluated following standard bioassay and biochemical techniques involving germination and growth of seedlings and mature plants. The aqueous leachates obtained from leaf, stem and root showed strong inhibiting effect on the growth and multiplication of P. hysterophorus. The leaf leachates were most toxic and in higher concentration (20% W/V) reduced the germination of Parthenium by 95%, total chlorophyll content by 82.4% and protein content by 65.5%. Stem leachates reduced germination by 15% and root and shoot growth by 29% and 26%, respectively. Post emergence application of leaf leachates severely affected the growth of Parthenium and wilting and chlorosis of seedlings, was noticed within 24 hrs of application.