Phytosociological Survey and Allelopathic Effects of Parhenium Weed in Comparison to Other Weeds in Pakistan

Parthenium weed (Parthenium hysterophorus L.) is an alien invasive weed of neotropical origin spreading rapidly in Punjab and North West frontier provinces of Pakistan. The present study was carried out to investigate the distribution of parthenium and its allelopathic effects against maize in comparison to native associated asteraceous weed species growing in wastelands district of Lahore. Survey revealed that parthenium weed is becoming a dominant part of local wasteland flora with the highest values of relative density and frequency as compare to other asteraceous weeds. Different concentrations of selected weed extracts failed to decline the germination of maize except higher (15%) concentration of S. arvensis that resulted in reduction of 28% in germination rate as compared to the control. Data recorded on shoot length of maize reflected that the lower concentrations of C. arvense significantly suppressed the shoot length and biomass of maize. Shoot biomass of maize was again significantly reduced even at lower concentrations of A. conyzoides and C. arvense. Interestingly, Inula sp. extracts at all test concentrations resulted in an increased biomass of maize. Root length and biomass appeared to be most sensitive part of maize and retarded significantly in response to different concentrations of extracts of all the test species except for Inula sp.