Pedosphere 24(5): 690--698, 2014
ISSN 1002-0160/CN 32-1315/P
©2014 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effect of nitrogen starvation on the responses of two rice cultivars to nitrate uptake and utilization |
YIN Xiao-Ming, LUO Wei, WANG Song-Wei, SHEN Qi-Rong and LONG Xiao-Hua |
| College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China) |
| ABSTRACT |
| Ammonium (NH+4) is the main nitrogen (N) form for rice crops, while NH+4 near the root surface can be oxidized to nitrate (NO-3) by NH+4 oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3 stored in the tissue and vacuolar between two rice (Oryza sativa L.) cultivars, Yangdao 6 (YD6, indica) with a high N use efficiency (NUE) and Wuyujing 3 (WYJ3, japonica) with a low NUE and measured the uptake of NO-3, expression of nitrate reductase (NR), NO-3 transporter genes (NRTs), and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1 NO-3. The results showed that both tissue NO-3 concentration and vacuolar NO-3 activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3 uptake (maximum uptake velocity, Vmax) than the cultivar WYJ3. Furthermore, YD6 had significantly higher leaf and root maximum NR activity (NRAmax) and actual NR activity (NRAact) as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3 re-utilization from the vacuole, and higher capacity for NO-3 uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3. |
| Key Words: nitrate reductase activity, nitrate transpoters, nitrogen use efficiency, Oryza sativa L., remobilization |
| Citation: Yin, X. M., Luo, W., Wang, S. W., Shen, Q. R. and Long, X. H. 2014. Effect of nitrogen starvation on the responses of two rice cultivars to nitrate uptake and utilization. Pedosphere. 24(5): 690-698. |
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