¹⁵N study on the partitioning of the nitrogen taken by soybeans from atmospheric dinitrogen, medium nitrate or ammonium

Partitioning and metabolism of nitrate, asparagine, and allantoin in the soybean shoots at the grain-filling stage

“…The fraction of asparagine-N distributed to the pods (grains+pod shells) was larger than that of nitrate-No The distribution pattern of allantoin-N was intermediate between that of nitrate-Nand asparagine-N: allantoin-N was distributed to both the leaves and pods. These results are in accordance with the previous observation (8) showing that in the intact plants at the reproductive stage, the large fraction of nitrate-N absorbed by the roots was distributed to the leaves, while the large fraction of fixed-N was distributed to the pods. Table 2 shows the distribution pattern of applied N in the N compounds of each plant part.…”

“…In the plants depending on the symbiotically fixed N, ureides are predominant N forms in the xylem sap, whereas the fraction of nitrate and/or amides increases in association with the decrease of ureides when combined forms of nitrogen (as nitrate, ammonium, or urea) are supplied (3,10). YONEYAMA and ISHlZUKA (8) have also shown that the patterns of primary distribution of N in soybean plants differed depending on the forms of N taken by plants. The form of N transported in the xylem stream is considered to be an important factor which controls the primary distribution of N (9).…”

“…Ten-day-old plants were transplanted to pots and grown in water culture in the greenhouse of NIAR up to the grain-filling stage. The culture medium was composed of the nutrients previously described (8), and nodules were well developed on the roots. Nine uniform plants were selected at the grain-filling stage, and cut at the stems (5 cm above the stem bases) under distilled water.…”

Relationships of dinitrogen fixation (acetylene reduction) with respiration, atp, and magnesium in soybean nodules

“…Akisengoku) were grown in water culture in a greenhouse, as described by YONEYAMA and ISHIZUKA (17). Two days before the assays of nitrogenase and respiratory activities were made, some plants were subjected to ringing operation at the stem base according to the method reported by YONEYAMA and IsHlZUKA (17) or treated with 200 ppm N as KNO a .…”

“…Akisengoku) were grown in water culture in a greenhouse, as described by YONEYAMA and ISHIZUKA (17). Two days before the assays of nitrogenase and respiratory activities were made, some plants were subjected to ringing operation at the stem base according to the method reported by YONEYAMA and IsHlZUKA (17) or treated with 200 ppm N as KNO a . From the plants at the podsetting stage (Experiment 1) and pod-filling stage (Experiments 2, 3, and 4), the nodules were separated one by one during the daytime (10:00 to 16:00), and used for the determination of acetylene reduction and CO 2 evolution by incubating them in small glass vials (5 ml) with addition of 20% C s H2 at room temperature.…”