关键词: 苹果, 枝条下垂, ¹⁵N尿素, 吸收, 利用, 分配

Abstract: Seven-year-old apple trees（Malus domestica Borkh.‘Red Fuji’）/Malus hupehensis were used in the present study to explore the effects of branch drooping on characteristics of absorption, distribution and utilization of ¹⁵N-urea through soil application in spring. Ndff value of roots in treated plant was obviously lower than that of control. Ndff value of fine roots was obviously different during multiple phenophases, while significant variance in Ndff value of coarse roots was found after fruit rapid-swelling stage. There was no regular pattern between Ndff value of leaves in short and middle shoots between the treatment and the control. Meanwhile, Ndff value of fruits, long shoot and leaves in long shoot with treatment was obviously lower than that of control before fruits were harvested, while Ndff value of perennial organs in treated plant was obviously higher than that of control after fruits were harvested. The ¹⁵N distribution ratio to short and middle shoots of treated plant was significantly higher than that of control，while difference of distribution to fruit between the treatment and the control was significant only after fruit rapid-swelling stage. Moreover, the distribution ratio to long shoot of treated plant was obviously lower than that of control before fruits were harvested. The ¹⁵N utilization ratio of treated plant was lower than that of control，and the significant difference was found after fruit rapid-swelling stage, the ¹⁵N utilization ratio of treated plant and control were 21.083% and 26.495% respectively.

Key words: apple, branch drooping, ¹⁵N-urea, absorption, utilization, distribution