分次追施N肥对苹果砧木—平邑甜茶吸收^(15)N-尿素以及叶片衰老的影响

Effects of fractionated nitrogen application on leaf senescence and^(15)N-urea uptake and utilization of apple rootstock—Malus hupenhensis

以盆栽平邑甜茶(Malus hupenhensis)为实验材料,研究等氮(N)量分次追施N肥(一次、二次和三次)对平邑甜茶叶片衰老及15N-尿素吸收、利用的影响。采用15N示踪技术,研究不同施肥处理下植株的生长、酶活性和15N吸收利用等参数。研究结果表明:植株的株高、茎粗、叶面积和叶绿素含量(SPAD)在生长前期均以一次性追肥处理最高,三次追肥处理最低,且与一次追肥处理差异显著;在生长中期均以二次追肥处理最高,一次追肥处理最低;在生长后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;叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性在生长前期均以一次追肥处理最高,三次追肥处理最低,且与一次追肥处理差异显著;在生长中期均以二次追肥处理最高,一次追肥处理最低;在生长后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;生长后期植株各器官从肥料中吸收分配到的15N量对该器官全N量的贡献率差异显著,三次追肥处理显著高于一次和二次追肥处理;生长后期三次追肥处理植株的总N量、吸收的15N量及15N肥料利用率均为最大。三次追肥处理能提高叶片全N量,延缓生长后期叶片衰老,提高N肥利用率。

Aims The effects of fractionated nitrogen （N） fertilization （once, twice and thrice） on leaf senescence and nitrogen uptake and utilization of potted Malus hupenhensis were explored using the ^15N labeling technique. Methods We measured growth parameters such as plant height, stem diameter, leaf area and chlorophyll content （SPAD）, enzyme parameters such as superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） in leaves and ^15 N parameters such as uptake and utilization for potted M. hupehensis under different fractionated N applications. Important findings Plant height, stem diameter, leaf area and SPAD were highest at early growth stage for once fractionated application and lower for twice fractionated application, and lowest for thrice fractionated application. At middle growth stage, twice fractionated application showed the highest values, while once fractionated application exhibited the lowest values. At the late growth stage, thrice fractionated application was the highest, while once fractionated application was the lowest. The leaf SOD, POD and CAT activities were highest for once fractionated application at early growth stage and lowest for thrice fractionated application. At the middle growth stage, twice fractionated application was the highest, whereas once fractionated application was lowest. At the late growth stage, thrice fractionated application showed the highest values, while once fractionated application had the lowest values. The ^15N derived from fertilizer （Ndff） value in different organs was significantly different. Thrice fractionated application demonstrated higher values than either of once and twice fractionated application at the late growth stage. Plant total N, ^15N uptake and N-usage efficiency were highest for thrice fractionated application at late growth stage. This indicates that thrice fractionated application not only can enhance the total N content of leaves and delay leaf senescence, but also can increase the N-usage efficiency.