Assimilation and transport of nitrogen in tulip (Tulipa gesneriana) as pursued by 15N
1991
Ohyama, T. (Niigata Univ. (Japan). Faculty of Agriculture)
Characteristics of assimilation and transport of nitrogen (N) in tulip plants were investigated mainly by a 15N tracer technique. Tulip roots accumulate a large amount of N (ca. 90 mgN/gDW) during winter, if N is available in the medium. The accumulated N in the roots originated mainly in absorbed N from the medium rather than from the bulb storage N. During the winter season, the accumulated N in some roots was not readily translocated to the other roots, suggesting that the nitrogen accumulated independently in each root. The accumulated N remained in soluble forms, especially glutamine was a major constituent. After sprouting in spring, the accumulated N in the roots was rapidly consumed for growth of leaves and stems. Some part on this N was redistributed to bulblets as the plants matured. The behavior of N accumulated in the roots during winter was basically similar to that of the bulb storage N. Thus, it may be concluded that the physiological role of the N accumulation in roots is to provide a sufficient amount of N required for a rapid growth of leaves immediately after sprouting. During this period, 4-methyleneglutamine was a major amino compound in leaves, stems and roots. The presence of this amide appeared to be a temporary storage of N in vegetative organs of tulip plants. The transport form of N in xylem was mostly glutamine, and 4-methyleneglutamine was not detected. A high accumulation (20-120 mg/gDW) of a novel organic acid, 2-oxo-4-methyl-3-pentene-1,5-dioic acid was found in leaves and stems. This acid seems to be a deamidation and deamination product of 4-methyleneglutamine
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