施氮水平对库尔勒香梨光合产物分配的影响

以6年生库尔勒香梨为材料,用¹³C脉冲标记技术研究了150、300、450 kg N·hm^-2(分别用N₁、N₂、N₃表示)3个施氮水平下树体各器官生物量、碳积累量以及¹³C同化物的吸收分配特性。结果表明: 库尔勒香梨树体整株的生物量、碳积累量、¹³C固定量以及叶片的同化能力均随着施氮水平的提高而增加;根冠比则随施氮水平的提高而降低。生殖器官果实的生物量、碳积累量在N₂处理下最高。树体各器官¹³C含量和分配率随施氮量的增加发生动态变化。新梢旺长期,叶片和根系对光合同化物的竞争能力较强,且¹³C分配率均为N₁处理下最高;果实膨大期和成熟期,叶片和果实的竞争能力较强,叶片¹³C含量和分配率在N₃处理下最高,而果实¹³C含量和分配率则在N₂处理下最大。综上,根据不同施氮水平各器官对碳同化物的吸收分配特征,以提高产量为目标,建议6年树龄的库尔勒香梨果园最佳施氮量为300 kg·hm^-2。

Effects of nitrogen application level on photosynthate distribution of Korla fragrant pear trees

Using ¹³C pulsed labeling technique, we examined the biomass and carbon accumulation of different organs as well as the distribution characteristics of ¹³C assimilate of 6-year-old Korla fragrant pear trees under three nitrogen application levels, i.e., 150, 300, and 450 kg N·hm^-2 (marked as N₁, N₂, and N₃, respectively). Results showed that the biomass, carbon accumulation, ¹³C fixation and leaf assimilation capacity of the whole pear tree increased while root to shoot ratio decreased with increasing nitrogen application. Both biomass and carbon accumulation amount of reproductive organs (i.e., fruits) were the highest under N₂ treatment. The ¹³C content and distribution rate of each organ changed dynamically along with increasing nitrogen application. At the new shoot growing stage, leaves and roots had stronger competitive abilities for photosynthate, with ¹³C distribution rates being the highest under N₁ treatment. During fruit swelling and mature stages, leaves and fruits were more competitive, with ¹³C content and distribution rate in leaves being the highest under N₃ treatment and those in fruits being the highest under N₂ treatment. According to the absorption and distribution characteristics of carbon assimilate across organs under the three nitrogen application levels, the optimal nitrogen application level for achieving high fruit yield in the 6-year-old Korla fragrant pear tree orchard is recommended as 300 kg·hm^-2 .