This study aimed to evaluate the bioactivity of hydroalcoholic extract of lemongrass on the germination and early growth of the weed plant beggartick (Bidens pilosa L.) and the test plant lettuce (Lactuca sativa L.). From the hydroalcoholic maceration of dried and cut leaves of lemon grass (127.46 g) in 1 L grain alcohol (70%), the following treatments were prepared, hydro-alcoholic (HA) extracts by diluting (v/v) the macerate in deionized water at 1:1 (HA1:1) and 1:2 (HA1:2) proportions, obtaining the respective dried extracts (DE) from the evaporation of the liquid phase of two 50-mL aliquots of each HA extract; after resuspension in the same water volume, one aliquot was autoclaved (1 atm for 15 minutes) resulting in HA1:1 and HA1:2 dried autoclaved extracts (DE1:1A and DE1:2A) and in dried non-autoclaved extracts (ES1:1 and ES1:2), and water as control. On the first day of bioassays, 2mL of treatments were applied, in completely randomized design, with 5 replicates. Germination percentage (G%), Germination Speed Index (GSI), shoot height (SH) and radicle length (RL) of achenes (25) of beggartick and lettuce were evaluated after having been distributed in Petri dishes and kept in a germination chamber (B.O.D.) for two weeks. HA1:1 and HA1:2 extracts inhibited G%, SH and RL of both species. All dried extracts reduced G%, GSI and CR of lettuce. For beggartick, only ES1:1 extract reduced G% while GSI was reduced in all extracts, except ES1:1A, but no extract influenced the early growth of this species.
allelopathy; dry extract; weed; medicinal plant