EFFECTS OF PLANT-GROWTH RETARDANTS AND RO OT PRUNING ON GROWTH AND YIELD OF TOMATO CULTURED HYDROPONICALLY AT HIGH-TEMPERATURE DURING SUMMER

The effects of the plant growth retardants, uniconazol at 1.25 and 2.5 ppm and paclobutrazol at 12.5 and 100 ppm and root pruning on the gro wth and yield of tomato plants cultured hydroponically at high tempera ture during summer were studied. 1. Growth of tomato seedlings was sup pressed by the plant growth retardants, especially with 100 ppm paclob utrazol or by root pruning. 2. All of plant growth retardants decrease d the number of nodes to the first truss and advanced anthesis. 3. Whe n plant growth retardants were applied to 2-leaf-old seedlings, stem r etardation was significant to the 2nd truss. 4. Plant growth retardant s advanced harvest of the Ist truss. 5. Fruit Brix and mean fruit weig ht were not influenced by the treatments. 6. Total yield of 1st and 2n d truss was slightly increased by root pruning. 7. Early fruit yield w as increased by the plant growth retardants.