Absorption, Distribution, and Translocation of Nitrogen at Growth Stages in Oilseed Rape Plant

Abstract

The differences of concentration and distribution of nitrogen in crop depend on organs and growth stages, and nitrogen redistribution in different organs will be occurred at different stages; these differences are related to the transfer of growth center. Consequently, the high crop yield depends not only on the high amount of nitrogen absorption, but also on the high efficiency of nitrogen redistribution. The objective of this study was to reveal the law of nitrogen absorption, distribution, and translocation in oilseed rape plant at different growth stages using two winter oilseed rape cultivars with the 15N labeling method in sand culture under Hoagland complete nutrient solution conditions. The results (average value from the two cultivars) indicated that 83.5% of nitrogen absorbed at the seedling stage, and 67.3% of nitrogen absorbed at the stem elongation stage, were distributed to leaves; 79.1% of the nitrogen absorbed at flowering stage was contained in leaves and stems, with 42.8% of it in the leaves. However, 42% of the nitrogen absorbed at siliquing stage was distributed to siliquae which is just the organ directly distributed the highest proportion of nitrogen absorbed at this stage. The nitrogen absorbed at four growth stages (seedling, stem elongation, flowering, and siliquing) translocated from the vegetative to the reproductive organs at 34.4%, 44.3%, 41.2%, and 31.7%, i.e. 203.2, 325.8, 218.0, and 82.0 mg plant-1, respectively. The translocated nitrogen from vegetative organs to the total nitrogen in seed accounted for 65.1%; among with 25.8% absorbed at the stem elongation stage, 16.9% absorbed at flowering stage, 15.9% absorbed at seedling stage, and 6.4% absorbed at siliquing stage, respectively. The proportion of nitrogen loss, after being absorbed at the four growth stages, was 24.0%, 10.5%, 11.7%, and 7.3 %, i.e. 141.6, 79.2, 43.2, and 16.2 mg plant-1, respectively. To sum up, nitrogen absorbed by roots at the earlier growth stages in oilseed rape was mainly translocated to leaves first, and then to the reproductive organ at the later growth stages.