Effects of plant growth retardants and root 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 growth and yield of tomato plants cultured hydroponically at high temperature during summer were studied. 1. Growth of tomato seedlings was suppressed by the plant growth retardants, especially with 100 ppm paclobutrazol or by root pruning. 2. All of plant growth retardants decreased the number of nodes to the first truss and advanced anthesis. 3. When plant growth retardants were applied to 2-leaf-old seedlings, stem retardation was significant to the 2nd truss. 4. Plant growth retardants advanced harvest of the Ist truss. 5. Fruit Brix and mean fruit weight were not influenced by the treatments. 6. Total yield of 1st and 2nd truss was slightly increased by root pruning. 7. Early fruit yield was increased by the plant growth retardants.