年橘留树保鲜过程中对^(15)N的吸收和分配研究

Absorption and Distribution of ^(15)N in the Nianju During Refreshment on Trees

为弄清年橘留树保鲜期间不同组织对氮素营养的吸收和分配情况,将稳定同位素^(15)N-尿素涂抹在5年生枳砧年橘叶片和果实后,分6个时期(6~480 h)取样分析果实和树体中不同部位^(15)N元素的含量。结果表明:年橘留树保鲜期间留果枝条对氮素的转运和分配与采果枝存在差异,涂抹^(15)N后丰度下降速率不同,留果树的无果枝平均下降速度达12.64%,采果后的枝条仅4.69%,留果树的有果枝居中,说明留树保鲜树体新梢是第一氮营养分配中心,果实是第二氮营养分配中心;没有留树保鲜的采果枝条,新梢是主要的氮营养分配中心。涂抹在叶片上的氮素可转运到果实,涂抹在果皮上的氮素经果实吸收后也可转运到叶片。叶片吸收的氮转运到新梢的含量显著高于转运到留树果实的氮含量,表明留树保鲜期内没有改变树体氮素的分配模式,从营养角度解释年橘留树保鲜不影响第二年产量的原因,为年橘留树保鲜期间合理施肥提供科学依据。

To give insight into the uptake and distribution of nitrogen in Nianju（ Citrus reticuiata Blanco） during fruits on tree storage, the leaves and fruits of 5-years old Nianju/Poncirus trifoliate were scribbled with stable isotope^15N-labelled urea and the contents of^15N from fruits and other parts of tree were detected at 6 different phases after treatment. The results indicated that different types of shoots had different characteristics of nitrogen translocation and distribution during refreshment on trees. The Ndff（^15N derived from fertilizer） of the middle leaves scribbled15 N dropped in different rate. The average decline rate of^15N abundance in the bearing shoots with refreshment on trees was higher than the harvested bearing shoots（with the ratio of 4.69%）, but lower than vegetative shoots（12.64%） after treated with ^15N-urea, suggesting that new shoots rather than fruits were the first distribution center of nitrogen. The absorbed ^15N in the leaves could be transferred to the fruits and vice versa.However, the content of15 N transferred from leaves to new shoots was significantly higher than that transferred from leaves to fruits, indicating that the inherent nitrogen distribution pattern did not change during refreshment on trees. Taken together, the results obtained above offer a rational explanation for why appropriate refreshment on trees do not influence the yield of next year from nutritional point and provide a scientific basis for reasonable fertilization during refreshment on trees in Nianju.