以15年生红富士苹果/八棱海棠为试材,研究等氮量分次追施氮肥对红富士苹果叶片衰老及15N吸收、利用的影响。结果表明,叶片叶绿素含量和超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性在盛花期均以一次性追肥处理最高,二次追肥处理次之,三次追肥处理最低,且与一次追肥处理差异显著;在花芽分化期均以二次追肥处理最高,三次追肥处理次之,一次追肥处理最低;在果实采收期均以三次追肥处理最高,一次追肥处理最低,且与三次追肥处理差异显著;三个追肥处理的叶片全氮含量在盛花期和花芽分化期差异不显著,而在果实采收期以三次追肥处理最高,二次追肥处理次之,一次追肥处理最低,且与三次追肥处理差异显著;不同追肥次数处理,果实成熟期植株各器官Ndff值差异显著,三次追肥处理显著高于一次和二次追肥处理;在盛花期叶片中的Ndff值一次追肥处理最大,在花芽分化期二次追肥处理最大,在果实成熟期三次追肥处理最大。果实成熟期三次追肥处理植株的总氮量、吸收的15N量及15N肥料利用率均为最大。%The effects of leaf senescence and the characteristics of absorption and utilization of fifteen-year-old ＇Fuji＇ apple （Malus robusta Rehd） in response to topdressing nitrogen were explored in the study. The results show that the SPAD and activities of SOD, POD and CAT are obviously the highest in one-time topdressing application at full-bloom stage, and then in two-times topdressing application, and the last is the three-time topdressing application. At the flower bud differentiation stage, the two-time topdressing application is the highest, and then the three-times topdressing application, and the lowest is maturity stage, the three-time topdressing application is obviously one-time topdressing application. At the fruit the highest, while the one-time topdressinzapplication is the lowest. At the full-bloom stage and flower bud differentiation stage, the total N contents ot leaves of the topdressing nitrogen application are not obviously different, while at the fruit maturity stage, the three-times topdressing application are obviously the highest, and then the two-time topdressing application, and the lowest is the one-time topdressing application. The proportions of N derived from the fertilizer （Ndff） in different organs are significantly different, and the Ndff values of the three-time topdressing application are obviously higher than those of the one or two-time topdressing. The leaf Ndff value is the highest in the one-time topdressing application at thefull -bloom and at fruit uptake and stage. stage, the highest value is the two-time topdressing application at the flower bud differentiation stage, maturity stage, the highest value is in the 15N-urea use efficiency are the highest in three-time topdressing application ; Plant total nitrogen, 15N the three-times topdressing application at the fruit maturity
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