等量分次施氮对冬枣^(15)N和^(13)C利用与分配特性的影响

Effects of multiple times of topdressing nitrogen application under equal level on utilization and distribution characteristics of ^(15)N and ^(13)C in winter jujube

以4年生盆栽冬枣为试材,采用^(13)C、^(15)N双标记示踪技术,在果实发育期研究了等氮量分次追施氮肥对冬枣植株^(15)N和^(13)C吸收、利用、积累和分配的影响.结果表明:至果实采收期,冬枣各器官Ndff值(植株器官从肥料中吸收分配到的^(15)N量对该器官全氮量的贡献率)随追氮次数的增多而显著增大.生殖器官(果实)和营养器官(叶片、枣吊、新生枣头枝和细根)的^(15)N分配率以4次追氮处理最高,1次追氮处理最低,贮藏器官(主干、多年生枝和粗根)^(15)N分配率的趋势相反;4次追氮处理^(15)N利用率分别比1次和2次追氮处理高27.4%和15.5%.追氮次数越多,植株总氮量和^(15)N吸收量越大;随时间的推移,1次追氮处理土壤^(15)N丰度和总氮含量持续降低,2次追氮处理呈先升高后降低的趋势,4次追氮处理变化相对最为平稳,至处理后期显著高于其他处理;果实白熟至采收期,叶片叶绿素、氮含量和净光合速率均表现为4次追氮>2次追氮>1次追氮.不同处理^(13)C同化物积累与分配不同.4次追氮处理^(13)C固定总量分别是1次和2次追氮处理的1.1和1.2倍.增加追氮次数,促进了^(13)C同化物向果实和贮藏器官的转移,而减少了向当年生营养器官的分配.综上,果实发育期4次追氮通过保证根层稳定、充足的氮素供应,提高了对氮素的吸收和利用,进而维持了较高的净光合速率,促进并优化了光合同化物的积累和分配,最有利于冬枣树体的生长及产量和品质的提高.

We explored the effects of multiple times of topdressing nitrogen application under equal level on the characteristics of absorption,utilization,accumulation,and distribution of 15N and 13C in four-year-old potted winter jujube during fruit developmental periods using the stable isotope tra-cer technology.The results showed that with the increases of nitrogen application times,the 15N derived from fertilizer(Ndff)in each organ significantly increased at the fruit maturity.The distribution rates of 15N in reproductive organ(fruit)and vegetative organs(leaf,deciduous spur,new branch,and fine root)were highest under four-time application,and lowest under one-time application.The opposite pattern was observed in storage organs(trunk,perennial branch,and coarse root).The 15N utilization rate under four-time application was 27.4%and 15.5%higher than one-time and two-time application,respectively.The more times N being applied,the more total N content and 15N absorption amount of plant.Soil 15N abundance and total N content continued to drop under one-time application and increased at the beginning and then declined with the time under two-time application.The relatively stable soil 15N abundance and total N content appeared in four-time application,which was significantly higher than those in the other treatments in later treatment stages.The chlorophyll content,leaf nitrogen content and photosynthetic rate displayed an order of four-time application>two-time application>one-time application during fruit white-mature period to fruit harvest period.The accumulation and distribution of 13C varied across different treatments.Increasing nitrogen application times would promote more 13C being transported to fruit and storage organs but decrease that in annual vegetative organs.Our findings indicated that four-time nitrogen application could enhance and optimize the accumulation and distribution of photosynthetic products by ensuring steady and adequate supply of nitrogen and improving the absorption and utilization of nitrogen during fruit development period,which facilitates the growth,yield and quality of winter jujube.