N-Methylpretrichodermamide B (I), pretrichodermamide C (H), quinolactacide (III) and 8-methoxy-3,5-dimethyl-3,4-dihydro-IH-isochromen-6-ol (IV), isolated from the marine fungus Penicillium sp., were examined for their ability to stimulate growth of seedling roots of buckwheat (Fagopyrum esculentum Moench), wheat (Triticum aestivum L.), soy {Glycine max (L.) Merr.}, and barley (Hordeum vulgare), It was shown that the stimulatory effects depend on the chemical structure of the compounds and on the plant species. Compounds I and III improved the rate of growth of seedling roots of buckwheat (1) and wheat (2), compound II stimulated growth of buckwheat roots (1), and compound IV improved growth of seedling roots of wheat (2) and soy (3). These compounds can be recommended for field study as plant growth stimulators.