p-CPA enhances growth and quality of muskelon fruits

The effects of para-chlorophenoxyacetic acid (p-CPA) application in improving the reduction in growth rate and sugar accumulation, and on the peel color and firmness of parthenocarpic fruit, and its residual content in the treated fruit were examined. p-CPA application to parthenocarpic fruit during the rapid growth stage [5 or 10 days after anthesis (DAA)] enhanced the fruit weight, but was ineffective when applied at 40 DAA. p-CPA--promoting of fruit growth increased as the applied concentration rose, so the weight of fruit treated by p-CPA at 500 mg L-1 (the highest level) was the greatest in all plots; however the peel was considerably softer and abnormal swelling occurred in the net. p-CPA applied to parthenocarpic fruit from 5 to 25 DAA increased sucrose content, the most effective application time being just before the onset of sucrose accumulation (25 DAA). Fructose and glucose contents were considerably lower than that of sucrose, and were not affected by p-CPA. p-CPA promoted sucrose accumulation when applied to pollinated fruit, which showed the highest level of enhancement in all plots. During the maturation period, the peel of parthenocarpic fruit was a darker green color and the netting did not fully develop compared to pollinated fruit. p-CPA applications at 10 or 25 DAA improved the peel color and netting of parthenocarpic fruits; therefore, the L value was similar to that of seeded fruit and the hue angle declined. Applications of p-CPA during the early growth stage reduced the firmness of the mesocarp concomitant with increases in the applied concentrations. p-CPA was present in the fruit at harvest, when applied from 10 to 25 DAA, even at 20 mg L-1. The residue level increased as the applied concentration rose, but p-CPA was not detected in the non-treated plot.