施氮量对冬小麦灌浆期光合产物积累、转运及分配的影响

采用花前¹⁴C-同位素标记旗叶的方法, 研究了盆栽条件下不同施氮量对两种穗型冬小麦品种光合产物转运及¹⁴C同化物积累、分配的影响。结果表明, 冬小麦成熟期¹⁴C-同化物主要分配在茎鞘中, 其分配率为44.31%~60.96%; 其次在籽粒中, 分配率为31.81%~40.67%; 其中大穗型品种兰考矮早八茎鞘、叶片中的分配率高于多穗型品种豫麦49-198, 表明成熟时大穗型品种有更多的同化物滞留在茎鞘和叶片中。施氮量对¹⁴C-同化物分配率有影响, 在施氮量36 g m^-2处理的茎鞘中分配率下降, 而籽粒中的分配率增加, 表明增施氮肥促进花前同化物向籽粒中分配。随着籽粒灌浆进程, 光合产物在营养器官中的分配率逐渐下降, 在籽粒中的分配率逐渐增加, 表明营养器官的同化物逐渐向籽粒转运。小麦籽粒的同化物有34.94%来自花前贮藏物质的转运, 65.06%来自开花后同化量, 但不同品种、不同氮素水平处理之间有较大差异。施氮量36 g m^-2处理的花前转运量、转运率、花前贮藏物质对籽粒贡献率均下降, 但花后同化量、对籽粒贡献率以及单穗粒重均增加; 其中兰考矮早八和豫麦49-198的花后贡献率分别为77.84%和56.29%, 表明兰考矮早八花后同化量对籽粒的贡献大于豫麦49-198。两品种籽粒产量均表现为施氮量36 g m^-2处理高于18 g m^-2处理, 并且大穗型品种的增产幅度大于多穗型品种, 表明增施氮肥对不同冬小麦品种的增产效应存在差异。

Effects of Nitrogen Application Rates on Accumulation, Translocation, and Partitioning of Photosynthate in Winter Wheat at Grain Filling Stage

Grain yield is mainly contributed by photosynthate post anthesis in wheat (Triticum aestivum L.), but assimilate accumulation before flowering also plays an important role, especially under stress conditions. The effects of nitrogen fertilizer on assimilation and partitioning of carbohydrate at maturity have been studied in different experiments with different conclusions. To evaluate the dynamic changes of assimilation and carbohydrate partitioning in wheat organs under different nitrogen application rates, a poly-spike cultivar Yumai 49-198 and a large-spike cultivar Lankao Aizao 8 were used in a pot experiment in 2005–2006 growth season. The nitrogen fertilizer was applied (half basic application and half topdressing at jointing) at two levels of 18 g m^-2 and 36 g m^-2 respectively. Flag leaves were labeled by ¹⁴CO₂ at pre-anthesis stage. The results indicated that the ¹⁴C assimilates photosynthesized at pre-anthesis mainly distributed in stem and sheath, next in grain at maturity. The proportion of ¹⁴C partitioned to stem and sheath, grain was 44.31–60.96% and 31.81–40.67% respectively. In comparison, the proportion of ¹⁴C partitioned to grain was increased, while to stems and sheath was reduced by increased N application. The percentage of assimilated ¹⁴C in stems and sheaths of Lankao Aizao 8 was greater than that of Yumai 49-198. There was 34.94% of the assimilates in grains de-rived from the reallocation of assimilate stored at pre-anthesis and 65.06% from photosynthate post anthesis. Moreover, transloca-tion amount, translocation proportion and contribution of assimilates before flowering to grains decreased with higher nitrogen application rate, while the contribution of assimilates post anthesis and grain weight per spike increased. The results also showed that the percentage of post anthesis assimilation to grains was 77.84% and 56.29% for Lankao Aizao 8 and Yumai 49-198, respec-tively, indicating that assimilates photosynthesized post anthesis in Lankao Aizao 8 was greater than that in Yumai 49-198. Finally, grain yield in 36 g m^-2 N treatment was higher than that in 18 g m^-2 N treatment. Meanwhile, increase range in grain yield of Lankao Aizao 8 both in treatments of 36 g m^-2 and 18 g m^-2 was greater than that of Yumai 49-198, indicating that the effect of nitrogen fertilizer on Lankao Aizao 8 was significantly greater than that of Yumai 49-198.