CPPU (Re-treatment), 4-CPA and NAA Improve the Growth and Quality of Parthenocarpic Melon Fruit Induced by CPPU.

Solutions of 1- (2-chloro-4-pyridyl) -3-phenylurea (CPPU), α-napthalenacetic acid (NAA), and p-chlorophenoxyacetic acid (4-CPA) applied once or twice to the parthenocarpic fruit induced by CPPU at anthesis, and their effects on the growth and quality of the fruit were investigated. Non-pollinated flowers treated with CPPU produced parthenocarpic fruit with 100% fruit set. CPPU treatment at anthesis enlarged fruit until 5 d after anthesis, but then the growth of the fruit was exceeded by the seeded fruit (control) . Both the 2nd CPPU treatments to the CPPU induced parthenocarpic fruit on the 10th day after anthesis and the 3rd CPPU treatment on the 25th day after anthesis enhanced the fruit growth. The first NAA and 4-CPA treatment to the fruit on the 10th day after anthesis and/or the second treatment on the 25th day after anthesis enhanced the fruit growth. No significant difference existed in enhancing the fruit growth between the three plant growth regulators. CPPU treatment to the pollinated flower did not influence the sugar accumulation of the fruit. The sugar content in parthenocarpic fruit induced by CPPU was significantly lower than in seeded fruit, this difference was more substantial in the placenta than in the mesocarp. Both the 2nd and 3rd CPPU treatments and the 1st and 2nd NAA treatments to the CPPU induced parthenocarpic fruit did not improve sucrose accumulation of those fruits. However, the 1st and 2nd 4-CPA treatment to these CPPU induced parthenocarpic fruit could remarkably enhanced the sugar accumulation of the fruit. These results suggest that 4-CPA treatment is practical for improving of the growth and the sugar accumulation of parthenocarpic fruit induced by CPPU.