Distribution Characters of Absorption Nitrogen in Oilseed Rape (Brassica Napus L.) at Different Growth Stages

Abstract

Two winter oilseed rape varieties grown in sand culture were labeled with 15Nitrogen (15N) at different growth stages to show the route of nitrogen (N) absorption, distribution, and transfer in oilseed rape (Brassica napus L.). Averaged over the two varieties, 84% of the N absorbed at the seedling stage, and 67% of the N absorbed at the stem elongation stage were distributed into the leaves. Of the N absorbed at flowering stage, 43% was distributed into the leaves and 36% into stems. However, 42.4% of the N absorbed at siliquing stage was directly found into the silique. The proportion of the N redistributed from vegetative organs into reproductive organs was 34%, 44%, 41%, and 32%, at seedling, stem elongation, flowering, and siliquing stages, respectively. The amounts of N transferred were 203, 326, 218, and 82 mg per plant, respectively. This corresponded to 65% of the total in the grain. The proportions of N lost after absorption were 24%, 11%, 12%, and 7% at the four growth stages, respectively. The amounts lost were 142, 79, 43, and 16 mg per plant, respectively. N absorbed at early growth stages in oilseed rape was mainly distributed to the leaves first, and then redistributed to the reproductive organs later. This route provided most of the N for the reproductive organs.