Mint family plants, due to their high genetic diversity, do not have the same reaction to the light conditions. The growth characteristics of genotypes become different with changing the light spectra. In order to eva‎luate the reaction of three mint genotypes including peppermint (Mentha piperita, M. spicata, and M. longifolia) to artificial light levels (including red, blue, red + blue, white, and natural light) a factorial pot experiment was carried out based on randomized complete block design with four replications. The studied traits included chlorophyll index, leaf area and weight, canopy diameter, internode length, stem height, stem number and stem weight. Phenolic compounds of genotypes were also measured. Then, the allelopathic effect of genotypes grown under different light conditions was studied on the germination parameters of lettuce seed. According to the results, the quality of light had a significant effect on all the investigated characteristics. The red spectrum produced the highest number of stems, but the longest stems were observed in blue spectrum conditions and in M. longifolia. The combination of red + blue light produced the highest stem weight in M. piperita, which was significantly different from other treatments. Among the phenolic compounds, rosmaric acid was observed in more amounts in the treatments, and the highest amount of this compound was in red + blue light with 725 mg l-1 . M. longifolia had the least adverse effect on percentage and rate of germination, and other parameters of lettuce germination were less affected by M. longifolia. In general, the lowest allelopathic effect was observed in the M. longifolia, but the received light spectrum had no significant effect on allelopathic properties

جمشيد رزمجو , حسن كريم مجني

محمدرضا سبزعليان دستجردي

نعمت اله اعتمادي شلمزاري , محمدحسين اهتمام