Purpose. Evaluation the biological action of low molecular heterocyclic compounds derivatives of pyrimidine (LMHCDP) on tomato (Lycopersicon esculentum Mill.) plant growth and development.

Materials and methods. 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 have been tested. Laboratory, comparison, generalization and mathematical statistics.

Results. It was noticed that D1, D3, D4 and D5 increased tomato seed germination up to 19-20%. D5 significantly (to 44%) increased shoot height. D1, D2 and D3 increased the roots length up to 42%, 43% and 48% respectively. Also, it was found that the number of roots increase also after application of D1 (up to 41%) and D3 (up to 40%).

Conclusion. It has been established that compounds D1 and D3 can be used as potentially effective and environmentally safe growth regulators for both agricultural and biotechnological manipulations.