IN VITRO GERMINATION AND GROWTH RESPONSE OF PARTHENIUM WEED TO CHROMIUM (VI) STRESS
Parthenium (Parthenium hysterophorus L.) is an exotic weed that has spread in different parts of Punjab, Khyber Pakhtunkhwa and Kashmir at an alarming extent and is now threatening natural vegetations and ecosystems. In the present study, laboratory bioassays were carried out to evaluate the effect of heavy metal ion Cr(VI) on germination and root/shoot growth of parthenium. Five concentrations of the metal ion viz. 10, 20, 40, 80 and 160 ppm were used in the experiment. A gradual decline in germination and growth of seedlings was recorded with the increase in metallic ion concentration. Lower concentrations viz. 10, 20 and 40 ppm, reduced seed germination by 11, 15 and 37% over control, respectively. Likewise, 10, 20 and 40 ppm metal solution reduced shoot length by 35, 67 and 93%, root length by 69, 93 and 95%, and plant dry biomass by 47, 69 and 97% over control, respectively. An 80 ppm solution of Cr(VI) completely arrested the germination. This study concludes that parthenium is highly susceptible to Cr(VI) stress where an 80 ppm solution of these metallic ions can completely stop germination of parthenium seeds.