Plant secondary metabolites (PSM) are usually defined as plant products play secondary role in the plant development and survive. But modern molecular investigations convince us, that it isn’t true. Their role in the plant is more spacious and deep. Study genetic determinants of the fruit size in tomato, we came to a conclusion, that loci controlling the fruit shape and weight are involved in phytohormone signaling pathways and processes of primary and se-condary metabolism. The development and weight of the tomato fruit is closely related to the amount of primary and secondary metabolites. Modification the expression of genes associated with primary and secondary metabolism can change the organoleptic composition and weight of tomato fruits by adjusting the harvest index and distribution of carbohydrates, which will ultimately improve the biochemical composition of tomato fruits. Many of PSM show effects outside their functional role in the plant. Of all anticancer medicine compounds developed since the 1940s, 75% were based on natural molecules and 49% are still natural products containing secondary metabolites. In earlier investigations we show, that PSM of steroid glycoside class, depending on the concentration, have the protective effect against of plant pathogens, such as fungi and viruses.  The goal of studies is determine the role of exogenously applied secondary metabolites in the regulation the development of plants.  Object of studies were PSM and plants. PSM: linaroside (the sum of glicosides from Linaria vulgaris Mill.), trigonelloside (the sum of furostanolic steroidal glicosides from Tri-gonella foenum-graecum L.), and moldstim (the preparation based on furostanolic glycosides from seeds of Capsicum annuum) were obtained from IGPPP. Materials of studies were water solutions of PSM, which were used for seeds treatment. Plants: 3 varieties from Apiaceae family (Coriandrum sativum L., v. Jubilar; Anethum graveolens L., v. Rusich and Apium grave-olens L., v. Elixir) and 2 varieties of Japanese cabbage from Brassicaceae family (Salad Misuna – typical Japanese variety and Salut Jubileiu – new variety from FSVC). Materials of studies were seeds and above parts of plants.