The experiment took place in 2006 and 2008. In 2007, the study did not take place due to severe damage to the buds and flowers caused by a spring frost. The subjects of the experiment were 14-year-old 'Sampion' apple trees grafted on the MM 106 rootstock. The auxin NAA, at the concentrations of 20 and 60 mgl-1, and ethephon, at the concentrations of 200 and 600 mg l-1, were used in the experiment. Spraying was carried out at the end of blooming, after 80% of the petals had fallen off the crown. Five days after spraying, the quantity of ethylene evolved from the fruitlets was measured. Large quantities of ethylene evolving were observed after spraying with ethephon, especially when used at 600 mg l-1. Spraying with auxin solutions caused large quantities of ethylene to be observed only during the first year of the study, two days after spraying with the 60 mg l-1 solution of NAA. From the third day after spraying with NAA, ethylene evolution from the fruitlets was observed to be only slightly higher than in the control. During the second year of the study, treatment with NAA caused a slight increase in ethylene evolution only during the first day after treatment. During subsequent days the evolved quantity of ethylene did not differ significantly from the control. In spite of the significant difference in the quantity of the ethylene evolved from the fruitlets, the percentage of the fruitlets was similar after using the agents at the higher concentrations: ethephon at 600 mgl-1 and NAA at 60 mgl-1, as well as at the lower concentrations. The treatments had only a slight influence on the reduction in the total yield. However, they were found to have a favourable influence on fruit size. The results of the study show a higher percentage of fruit with a diameter exceeding 7 cm in the total yield.
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