Allelopathic effect of bha-yha (Asystasia gangetica) on growth of lettuce.
Bha-yha (Asystasia gangetica) is an invasive weed widely distributed in an agricultural area of Thailand. Allelopathy is a potential mechanism for an invasion behavior as invasive weeds can produce allelochemicals for inhibiting growth of adjacent plants. Objectives of this present study were to investigate the allelopathic effects of bha-yha water extracts and soil incorporated with bha-yha powder on growth of lettuce (Lactuca sativa). Results showed that the concentration of bha-yha water extracts at 0.05 g/ml were highly inhibited the root length and dry weight of lettuce by 43% and 57%, respectively compared with other concentrations. Soil incorporation with bha-yha powder at 0.05 g/g (soil) were highly inhibited the shoot length and root length of lettuce by 48% and 59%, respectively compared with other concentrations. In addition, the bha-yha water extracts and soil incorporation with bha-yha powder from the shoot part was significantly inhibited the growth of lettuce more than the root part of bha-yha. Therefore, the results suggested that bha-yha had an allelopathic property.