Effect of nitrogen on apple fruit hormone changing trends and development

Eight-year-old apple trees (M. domestica Borkh. cv. Red Fuji/M. hupenensis Rhed) as materials were used to study the effect of N on fruit development under heavy thinned condition. The main results were as follows: The single fruit weight of N treatment and control did not existed significant deference in 105 d after flowering, control fruits were heavier than N treatment from 105 d to 130 d due to its fruits beginning rapid growth period 7 d earlier than N treatment, but the average single fruit weight in N treatment was heavier than control at harvest for control fruits suspending growth 7d earlier than N treatment. N fertilization influenced GA, ZRs , ABA and IAA concentrations and its change trends in flesh , particularly increased the four hormone concentrations in flesh cell enlargement period. But the hormone concentration peak values appearance time were later 12 weeks than nonfertilized controls. GA, ABA and IAA concentration peak values appearance time was slightly ahead of fruit RGR(relative growth rate) peak values appearance time. The length of fruit growth period was prolonged and the single fruit weight was increased by plant growth regulator in control trees. These results indicated that N regulated fruit development by influencing fruit hormone concentration. In N treatment fruits, the water content, pericarp chlorophyll, titratable acid concentration were increased, but anthocyanin and flesh soluble sugar concentration were decreased as fruits development trends changed.