Effect of Nitrogen Starvation on the Responses of Two Rice Cultivars to Nitrate Uptake and Utilization

• Published in: Pedosphere Vol. 24; no. 5; pp. 690 - 698
• Main Authors: YIN, Xiao-Ming, LUO, Wei, WANG, Song-Wei, SHEN, Qi-Rong, LONG, Xiao-Hua
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2014; College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095(China)
• Subjects: nitrate reductase activity; nitrate transpoters; nitrogen use efficiency; NR活性; Oryza; Oryza sativa; Oryza sativa L; remobilization; 吸收; 氮素利用效率; 氮饥饿; 水稻品种; 硝酸盐; 硝酸还原酶; Oryza sativa L; nitrogen use efficiency; nitrate reductase activity; nitrate transpoters; remobilization
• ISSN: 1002-0160; 2210-5107
• DOI: 10.1016/S1002-0160(14)60055-2

Ammonium（NH＋4） is the main nitrogen（N） form for rice crops, while NH＋4near 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-3stored 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-3transporter genes（NRTs）, and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity 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-3uptake（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-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.