Journal of Experimental Botany, Vol. 52, No. 355, pp. 277-283,
February 2001
© 2001 Oxford University Press
Original Papers |
Rapid N transport to pods and seeds in N-deficient soybean plants
1 Faculty of Agriculture, University of Niigata, 2-8050 Ikarashi, Niigata-city, Niigata 951-2181, Japan
2 Department of Radioisotopes, Japan Atomic Energy Research Institute, Gunma 370-1207, Japan
3 Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Gunma 370-1207, Japan
4 Central Research Laboratory, Hamamatsu Photonics Co., Shizuoka 434-0041, Japan
Non-nodulated soybean (Glycine max (L.) Merr.) plants were cultivated hydroponically under N-sufficient (5 mM NaNO3) or N-deficient (0.5 mM NaNO3) conditions. 13N- or 15N- labelled nitrate was fed to the cut end of the stems, and the accumulation of nitrate-derived N in the pods, nodes and stems was compared. Real-time images of 13N distribution in stems, petioles and pods were obtained using a Positron Emitting Tracer Imaging System for a period of 40 min. The results indicated that the radioactivity in the pods of N-deficient plants was about 10 times higher than that of N-sufficient plants, although radioactivity in the stems and nodes of N-deficient versus N-sufficient plants was not different. A similar result was obtained by supplying 15
to cut soybean shoots for 1 h. The fact that the N translocation into the pods from
fed to the stem base was much faster in N-deficient plants may be due to the strong sink activity of the pods in N-deficient plants. Alternatively, the redistribution of N from the leaves to the pods via the phloem may be accelerated in N-deficient plants. The temporal accumulation of 13
in nodes was suggested in both N-sufficient and N-deficient plants. In one 13
pulse-chase experiment, radioactivity in the stem declined rapidly after transferring the shoot from the 13
solution to non-labelled NO3; in contrast, the radioactivity in the node declined minimally during the same time period.
Key words: Soybean, nitrogen deficient, nitrogen requirement, nitrate translocation, PETIS.
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