Comparison of allelopathy potential between an exotic invasive weed Alternanthera philoxeroides and a local weed A. sessilis.

To estimate the allelopathy potential of Alternanthera philoxeroides, the inhibition rates of different organs of the exotic invasive weed A. philoxeroides on seedlings of lettuce (Lactuca sativa L.) and barnyardgrass [Echinochloa crusgalli (L.) Beauv. var. mitis (Pursh) Peterm.] were measured with a Chinese native weed A. sessilis as a control by the sandwich method. Under the treatment of 50 mg leaves of A. philoxeroides, the root growth of the lettuce and barnyardgrass was inhibited by 81% and 51%, respectively, and for the shoot growth by 49% and 48%, respectively, significantly higher than the control. However, there were no significant difference compared with that of the treatment of A. sessilis. The inhibition rate on the root length of barnyardgrass was 54% on average under the treatment of the root of A. philoxeroides, much higher than that of the treatments of its stem and leaf. In addition, with the dose of sample of A. philoxeroides increasing, the inhibition rate against the root growth of lettuce enhanced significantly, and the values were 54%, 61% and 83% under the treatments of 10 mg, 30 mg and 50 mg leaf of A. philoxeroides, respectively.