Plant growth regulators were treated either individually or as mixture of two or three hormone to assess capability for production of seedless watermelon. Each treatment was repeated at 6-day intervals to further identify effective methods of treatment. The results are as follows;
1. GA₃ 2,000 ppm had no effects on fruit set. Single treatment of NAA 2,000 ppm, BA 2,000 ppm or 50% Tomatotone (50 percent concentration) resulted in low fruit set percentage. However, the mixture of either Tomatotone plus BA or Tomatotone plus GA₃ led to 100 percent fruit set.
2. The mixture of either 50% Tomatotone plus GA₃ (1,000 to 2,000 ppm) or 50% Tomatotone plus BA (1,000 to 2,000 ppm) resulted in high percentage of marketable fruits. However, fruit drop was observed during the diameter growth period caused by the addition of NAA (2,000 ppm) to either of Tomatotone, GA₃, or BA.
3. The promotive effects of the growth regulators treatment on fruit diameter growth were reduced rapidly after 6 days, and were almost disappeared after 10 days.
4. The mixture of 50% Tomatotone, GA₃ 2,000 ppm, and BA 1,000 ppm was treated on the ovary and the peduncle. Then mixtures of 50% Tomatotone plus GA₃ 2,000 ppm or 50% Tomatotone plus BA 1,000 ppm were treated repeatedly on the peduncle 6 days after the first treatment. Both of these 2 treatments were found to be the best methods among all treanients throughout this experiment for securing good-quality parthenocarpic fruits.
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