Allelopathic potential of Allamanda cathartica L. under different screening conditions

Allamanda cathartica is an ornamental plant and is widely distributed in many areas of the world. This study aims to determine the allelopathic effects of this plant (leaf and stem dried powders) under bioassays and greenhouse conditions against the growth of Echinochloa crus-galli and some indicator plants. At the applied dose (50g/L) of the leaf powders, the root length of E. crus-galli and Bidens pilosa was significantly reduced by over 90%. Interestingly, rice growth was negligibly inhibited and the elongation of shoot and root was stimulated. In a greenhouse trial, the average inhibition of E. crus-galli growth was reduced by 54.9% at a dose of 50g/m 2 of the leaf powders. Moreover, the biomass of natural paddy weeds was significantly reduced by 46.4%. However, rice growth parameter was increased by about 20% at a dose of 12.5g/m 2 . The allelopathic property of the leaf powders showed higher than its stems. Consequently, our results indicated that A. cathartica possesses a strong allelopathic property and may be served this plant as a natural herbicide source to control paddy weeds and increase rice growth for sustainable agricultural production.