[Characteristics of absorption, utilization, and distribution of 15N-urea for Korla fragrant pear in spring.]

Six-year-old Korla fragrant pear trees were fertilized with 15N-labelled urea before early bud stage to examine the absorption, distribution, and utilization of urea. Results showed that there was a significant difference of 15N distribution rate in organs at different growth stages. 15N was pre-ferentially distributed in the roots , with Ndff (15N amount absorbed from the fertilizer contribution rate of the total nitrogen organ) being the highest in roots following by new shoots at full-bloom stage. During new shoot growing and fruit expanding stages, 15N absorbed in roots preferentially moved to new organs (leaves and new shoots), with 15N distribution rate to roots being continuously decreased. Fruits became the new distribution center with highest Ndff at harvest stage. The amounts of absorbed 15N in fruits accounted for 19.8% of total absorbed 15N in the tree. The utilization rate of 15N-labelled urea at current season increased gradually with the growth stages. The maximum value of utilization rate was 18.5%, which was observed at harvest stage.以6年生库尔勒香梨为试材,在春季香梨萌芽前施用15N尿素,研究香梨施用15N尿素的吸收、分配和利用特性.结果表明:不同生育期香梨吸收的15N在各器官的分配率存在显著差异,盛花期15N优先分配在根中,其Ndff(从肥料中吸收的15N量对该器官全氮量的贡献率)最高,新稍次之;新梢旺长期和果实膨大期根部吸收的15N优先向新生器官(叶和新稍)运转,根部15N的分配率不断下降;果实成熟期果实成为新的分配中心,其Ndff最高,果实累积的15N量占香梨树体总的15N吸收量的19.8%.香梨树体对土施15N-尿素肥料的当季利用率随生育期的推进而不断提高,到果实成熟期达到最大值(18.5%).