Effect of Isoproturon on Growth and Photosynthesis of Herbicide Ressitant and Susceptible Biotypes of Little seed Canary Grass

A pot culture study was conducted at CCS Haryana Agricultural University, Hisar revealed that on an average the per cent reductions in the dry weight of resistant biotypes of little seed canary grass (Phalaris minor Retz.) were 7.0, 10.3, 19.6 and 52.3 due to isoproturon applied at 0.125, 0.25, 0.5 and 1.0 kg/ha, respectively, whereas such reductions were upto 66.1, 81.9, 100 and 100% in case of susceptible biotypes at respective concentrations. The dose of isoproturon required to reduce the growth by 50% in resistant biotypes was 6.2 to 9.9 times higher as compared to the susceptible biotype. In all biotypes, rate of photosynthesis decreased upto 4th day following isoproturon treatment and then there was recovery in photosynthesis in the resistant biotypes from 5th day but not in susceptible biotypes.