Rapid N transport to pods and seeds in N-deficient soybean plants.
Non-nodulated soybean (Glycine max (L.) Merr.) plants were cultivated hydroponically under N-sufficient (5 mM NaNO(3)) or N-deficient (0.5 mM NaNO(3)) conditions. (13)N- or (15)N- 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 (13)N 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)NO(3) to cut soybean shoots for 1 h. The fact that the N translocation into the pods from NO(3) 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)NO(3) in nodes was suggested in both N-sufficient and N-deficient plants. In one (13)NO(3) pulse-chase experiment, radioactivity in the stem declined rapidly after transferring the shoot from the (13)NO(3) solution to non-labelled NO(3); in contrast, the radioactivity in the node declined minimally during the same time period.
Faculty of Agriculture, University of Niigata, 2-8050 Ikarashi, Niigata-city, Niigata 951-2181, Japan. ohtake@agr.niigata-u.ac.jp
N
N
Ohtake
T
T
Sato
H
H
Fujikake
K
K
Sueyoshi
T
T
Ohyama
N S
NS
Ishioka
S
S
Watanabe
A
A
Osa
T
T
Sekine
S
S
Matsuhashi
T
T
Ito
C
C
Mizuniwa
T
T
Kume
S
S
Hashimoto
H
H
Uchida
A
A
Tsuji
D000596:Amino Acids / Q000032:analysis; D005638:Fruit / Q000378:metabolism; D018527:Hydroponics; D007553:Isotope Labeling; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000008:administration & dosage / Q000172:deficiency / Q000493:pharmacokinetics*; D009590:Nitrogen Radioisotopes / Q000493:pharmacokinetics; D018520:Plant Shoots / Q000737:chemistry / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000378:metabolism*; D013025:Glycine max / Q000737:chemistry / Q000378:metabolism*; D014055:Tomography, Emission-Computed
D000596:Amino Acids; D009566:Nitrates; D009590:Nitrogen Radioisotopes; D009584:Nitrogen