Translocation of labelled nitrogen in oilseed rape

Summary

Plants of oilseed rape (Brassica napus L., cv. Loras) were grown hydroponically under controlled greenhouse conditions. Plants were treated with labelled nitrogen (¹⁵NH₄ ¹⁵NO₃) for four days at the beginning of stem elongation. Beginning at the day of flowering, plants were harvested at 12-day intervals. Total nitrogen (Kjeldahl) and labelled nitrogen (emission spectrography) were determined in young leaves, old leaves, hulls and seeds. Older leaves exhibited a continual decrease of labelled nitrogen while younger leaves and hulls accumulated ¹⁵N before it was exported. Most of the labelled nitrogen in leaves and hulls was ultimately translocated to seeds, which increased steadily in labelled nitrogen.