Oxirapentyn A (1), oxirapentyn B (2), and oxirapentyn E (3) were examined for their ability to stimulate growth of seedling roots of barley (Hordeum vulgare L.), buckwheat (Fagopyrum esculentum Moench), corn (Zea mays L.), soy {Glycine max (L.) Merr.}, and wheat (Triticum aestivum L.). It was shown that the stimulatory effects depend on the chemical structure of the oxirapentyns and on the plant species. Compounds 1, and 2 are efficient for growth of seedling roots of barley, and wheat, whereas compound 3, at different concentrations, stimulates growth of seedling roots of maize, soy, and wheat. These compounds can be recommended for field study as plant growth stimulators.