Allelopathic activity of coffee extracts: implications for germination and initial growth in select weeds and polyploidy in <i>Lactuca sativa</i> L

Coffee beans contain compounds with allelopathic activity, such that some beans that do not meet quality standards might rather be used to obtain a natural herbicide which consequently might be employed to control undesired plants and avoid economic losses. Thus, the objectives of this study were: (1) to investigate the allelopathic effect of different concentrations of green (GC) and roasted (RC) coffee extracts on the inhibition of germination and initial growth of <i>Lactuca sativa</i> L. <i>Bidens pilosa</i> L. and <i>Cyperus rotundus</i> L. and (2) determine the induction of changes in the cell cycle of <i>L. sativa</i> L. and (3) quantify some compounds in the GC and RC extracts with possible allelopathic effects. Seeds and tubers were sown on germination paper, moistened with water or different concentrations of extracts, stored in transparent plastic boxes, and maintained in a germination chamber. Caffeine was found at higher concentrations of 79.768 and 15.532 g/L in GC and RC extracts, respectively. In general, RC extract for <i>L. sativa L</i>. and GC for <i>B. pilosa L</i>. diminished germination parameters. For <i>C. rotundus L</i>. GC extract decreased growth regardless of the concentration. An increased frequency of cell cycle alterations was observed in the root cells of <i>L. sativa</i> L. This study is the first to report that the studied extracts possess allelopathic potential, as they are effective in reducing germination and/or initial growth of weed species and <i>L. sativa</i> L. as well as inducing alterations in the cell cycle of <i>L. sativa</i> L.