Experiments were conducted to investigate the effects of soaking seeds in potassium silicate and uniconazole on seed germination and seedling growth of two tomato cultivars. Tomato (Lycopersicum esculentum Mill. ‘Seogeon and Seokwang’) seeds were put in a Petri dish filled with 15 ml of a solutions containing either 50 or 100 mg L-1 potassium silicate or uniconazole and were placed in an environment controlled chamber (25°C, 80% RH, dark) for 12 or 24 h. After the soaking treatment, seeds were washed in distilled water and were dried in a growth chamber (25°C, 80% RH, and in the dark) for 4 h. Seeds were sown in 288-cell (11 cc) plug trays containing a Tosilee medium and trays were layed out in a randomized complete block design on beds in a glasshouse. A nutrient solution was supplied uniformly for all treatments once a day through a sub-irrigation system. Soaking seeds in potassium silicate or uniconazole solution reduced germination percentage in both cultivars when compared to the control. In both cultivars, soaking treatment of uniconazole significantly reduced length of stem, hypocotyls, internode, leaf area and dry weight of stem and root, as compared to the control and other treatments. Root length increased significantly in all treatments when compared with the control. Hypocotyl length and plant height of 'Seogeon' seedlings were suppressed in the 100 mg L-1 potassium silicate treatment as compared to the control and water soaking. In contrast, height of ‘Seokwang’ seedlings increased by potassium silicate treatment. The chlorophyll fluorescence ratio (Fv/Fm) increased by low concentration of uniconazole treatment as compared to the control and other treatments. The growth of tomato seedlings was efficiently regulated by uniconazole 50 mg L-1 (12 h soaking) treatment.Key words: Chlorophyll fluorescence, plant growth retardants, plug plants, potassium silicate, seed treatment, silicon, uniconazole
