Abstract
The accumulation of nitrite in nodules was investigated to elucidate the mechanism of inhibition of nitrogen fixation in nodules of soybean (Glycine max. [L.] Merr.) plants supplied with nitrate. Acetylene-reducing activity (ARA) in nodules fell within 24 h as a result of the supply of exogenous nitrate, accompanied by an increase in the accumulation of nitrite in the cytosol but not in the bacteroids of nodules. Nitrate reductase (NR) activity in the nodule cytosol remained high, irrespective of the supply of nitrate. Nitrosylleghemoglobin (LbNO) was detected spectrophotometrically in the extract from nodules in which nitrogen fixation was inhibited by nitrate. In experiments in vitro, it was found that LbNO was easily formed from leghemoglobin in the presence of nitrite and dithionite.Thus, it is suggested that nitrogen fixation was inhibited primarily by a decrease in the function of leghemoglobin, attributable to the formation of LbNO, which was caused by the accumulation of nitrite generated from nitrate by NR in the nodule cytosol.
| Original language | English |
|---|---|
| Pages (from-to) | 341-346 |
| Number of pages | 6 |
| Journal | Plant and Cell Physiology |
| Volume | 31 |
| Issue number | 3 |
| Publication status | Published - 1990 |
| Externally published | Yes |
Keywords
- Leghemoglobin
- Nitrate reductase
- Nitrogen fixation
- Nitrosylleghemoglobin
- Nodule
- Soybean
ASJC Scopus subject areas
- Physiology
- Plant Science
- Cell Biology