Functions of nitrogen accumulation and redistribution in leaves and its contribution to seed yield in soybean

大豆籽粒灌浆过程中，大量的氮素从营养器官重新分配到种子中。美林)。然而，叶片中分布的氮素对种子产量的影响尚不清楚。评价了氮素在叶片中的积累和再分配功能及其对种子产量的贡献。根据R5和R7阶段氮素含量的差异来估算氮素的再分配。各品种叶片含氮量在R5期以后开始下降，说明氮素重新分配的开始。在10个品种中，约有13.8%~37.9%的氮素是从叶片组织中重新分配的。种子产量与叶片重分配氮量呈正相关，而与R5叶片氮浓度和种子重分配氮比例无关。然而，在高产年份，种子产量与氮素再分配不太可能相关，即使最低的氮素再分配也与相对较高的种子产量有关。此外，在Schiyutaka中，提高氮素浓度在灌浆前增加了种子产量，这取决于氮素的再分配，而在Tamahomare中，提高了种子灌浆后的产量，这与氮素再分配无关。结果表明，氮素的大量再分配并不总是对种子产量有贡献，这意味着籽粒灌浆过程中的直接氮素吸收可能是不同品种种子产量的更重要因素。

It is well known that large amount of nitrogen are redistributed from vegetative organs to the seeds during seed filling in soybean (Glycine max [L.] Merrill). However, the role of distributed nitrogen from leaves on the seed yield production are not clear. The functions of nitrogen accumulation and redistribution in leaves and its contribution to the seed yield were evaluated. The redistributed nitrogen was estimated by the difference in the nitrogen contents between R5 and R7 stage. The nitrogen content in leaves began decreasing after R5 stage in all cultivars, indicating the start of nitrogen redistribution. About 13.8% to 37.9% of the total nitrogen in the seeds was estimated being redistributed from the leaf tissues among ten cultivars. The seed yield was correlated positively with the amount of redistributed nitrogen from leaves but with neither the nitrogen concentration in the leaves at R5 nor the proportion of redistributed nitrogen in the seeds. However, in high seed yielding year, the seed yield is not likely associated with nitrogen redistribution, even the lowest nitrogen redistribution was associated with relatively higher seed yield in Tamahomare. Furthermore, enhanced nitrogen concentration increased the seed yield before seed filling in Sachiyutaka, which is dependent on the nitrogen redistribution, whereas after seed filling in Tamahomare, which is independent of the nitrogen redistribution. The results indicated that large nitrogen redistribution does not always contribute to high seed yielding, implying the direct nitrogen uptake during seed filling could be more important factor for high seed yielding depend on the cultivars.