Effects of lemon balm (Melissa Officinalis L.) extract on germination and seedling growth of six plants

The n-hexane-, acetone- and water-soluble fractions obtained from an aqueou s acetone extract of lemon balm (Melissa officinalis L.) shoots inhibited t he germination and the growth of roots and shoots of cockscomb (Amaranthus caudatus L.), cress (Lepidium sativum L.), crabgrass (Digitaria sanguinalis L.), timothy (Phleum pratense L.), lettuce (Lactuca sativa L.) and ryegras s (Lolium multiforum Lam.). The inhibitory activity of the water-soluble fr action was the greatest, followed by that of acetone- and n-hexane-soluble fractions in all bioassays. The effectiveness of these fractions on the roo ts was greater than that of the shoots of the test plants. Significant redu ctions in the germination and growth of the roots and shoots were observed as the extract concentration increased. Such rate-dependent responses of th e test plants to the fractions suggest that each fraction might contain all elochemical(s), but that the greatest potential was in the water-soluble fr action.