Allelopathic Effect of Lemon Balm on Germination and Growth of Pea, Safflower and Wheat

ABSTRACT: In order to investigate the likely allelopathic potential of an aqueous extract and powder of lemon balm (Melissa officinalis) on the germination and seedling growth of pea (Cicer arietinum), safflower (Carthamus tinctorius L.) and wheat (Triticum sativum), an experiment was carried out at the laboratory and greenhouse of agriculture faculty of Shahid Bahonar University of Kerman, Iran, from October 2009 to March 2010. A completely randomized design with three replicates using five extract concentrations of lemon balm plant including 0, 25, 50, 75, and 100 g l-1 and four amounts of lemon balm powder including 0, 7.5, 15 and 30 g 2kg-1 of soil was employed in laboratory and greenhouse experiments respectively. All extract concentrations of lemon balm except 25 g l-1 inhibited pea and wheat seed germination significantly, but had no inhibitory effect on germination of safflower. The powder of mature lemon balm plants affected the fresh and dry weight and shoots elongation in these crops negatively compared with the control in all levels. Therefore use of this plant should be prevented in rotation or intercropping with these three crop plants. Further research conducted in the analytical laboratory as well as in the field is needed before a practical application of the extract and powder as weed inhibiting agent can be recommended