The aim of our research was an evaluation of biological activity of low molecular heterocyclic compounds’ derivatives of pyrimidine (LMHCDP) on tomato (Lycopersicon esculentum Mill.) plant and root formation both in vitro and in vivo conditions. The following compounds: D1 ‑ 8-(Methylsulfonyl)- 2,6-dihydroimidazo[1,2-c]-pyrimidin-5(3H)-one; D2 ‑ 9-(Methylsulfonyl)- 2,3,4,7-tetrahydro- 6H-pyrimido[1,6-a]pyrimidin-6-one; D3 ‑ 6-(2-Hydroxyethyl)-8-methylsulfonyl-2,6-dihydro-3H-imidazo[1,2-c]pyrimidine-5-one hydrochloride; D4 ‑ 7-(2-Hydroxyethyl)-9-methylsulfonyl-2,3,4,7-tetrahydropyrimido[1,6-a]pyrimidin-6-one hydrochloride; D5 – 9-(Methylsulfonyl)-7-propyl-2,3,4,7-tetrahydro-6H-pyrimido[1,6-a]-pyrimidine–6-one in 1x10^-8 M concentration were tested. For both in vitro and in vivo studies tomato cultivars ʻMoney Makerʼ was used. For in vitro study tomato seeds were surface-sterilized and then germinated on nutrient medium at 24^oC under long-day conditions (16 h light/ 8 h dark). Effects of D1-D5 on in vitro shoot regeneration (% per explant), root formation and growth on Murashige and Skoog (MS) medium supplemented with these compounds were evaluated. As control the distilled water and 1x10^-8 M indole-3-acetic acid (IAA) were used. Such biometrical parameters as % of germinated seeds, shoot height; root length; number of roots; fresh biomass; chlorophyll a and b content; total chlorophyll, carotenoids; total protein were evaluated.

It was found that IAA in 1x10^-8 M concentration does not cause any effects on tomato seeds germination or tomato plants growth and development both in vivo and in vitro experiments. D1, D3, D4 and D5 increased seed germination up to 19-20%. D5 significantly (to 44%) increased shoot height. Root length was increased after application оf D1 (up to 42%), D2 (43%) and D3 (48%). An increase in the number of roots was observed as a result of D1 (up to 41%) and D3 (40%) action. D1 increased also up to 14% carotenoid content.

Thus, we can postulate that compounds D1 and D3 in such a low concentration 1x10^-8 M are the most powerful inductors of morphogenesis and rhizogenesis in tomato plants. These LMHCDP could be used in agricultural technology as new effective and ecologically safe growth regulators as well as in different tomato biotechnological approaches and programs.