Pedosphere 16(6): 707--717, 2006
ISSN 1002-0160/CN 32-1315/P
©2006 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Nitrate effect on rice growth and nitrogen absorption and assimilation at different growth stages |
DUAN Ying-Hua , ZHANG Ya-Li, SHEN Qi-Rong and WANG Song-Wei |
| College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China). E-mail: yhduan@163.com |
| ABSTRACT |
| The effect of nitrate (NO3-) on rice (Oryza sativa L.) growth as well as N absorption and assimilation during different growth stages was examined using three typical rice cultivars. Dry weight, yield, N uptake, nitrate reductase activity (NRA) in leaves, and glutamine synthetase activity (GSA) in roots and leaves during their entire growth periods, as well as the kinetic parameters of ammonium (NH4+) uptake at the seedling stage, were measured with solution culture experiments. Results indicated that addition of NH4+-N and NO3--N at a ratio of 75:25 (NH4++NO3- treatment) when compared with that of NH4+-N alone (NH4+ treatment) increased the dry weight of ‘Nanguang' cultivar by 30% and ‘Yunjing 38' cultivar by 31%, and also increased their grain yield by 21% and 17%, respectively. For the four growth stages, the total N accumulation in plants increased by an average of 36% for ‘Nanguang' and 31% for ‘Yunjing 38', whereas the increasing effect of NO3- in the ‘4007' cultivar was only found at the seedling stage. In the NH4++NO3- treatment compared to the NH4+ treatment, NRA in the leaves increased by 2.09 folds, and GSA increased by 92% in the roots and 52% in the leaves of the three cultivars. NO3- supply increased the maximum uptake rate (Vmax) in the ‘Nanguang' and ‘Yunjing 38' cultivars, reflecting that the NO3- itself, not the increasing N concentration, increased the uptake rate of NH4+ by rice. There was no effect on the apparent Michaelis-Menten constant (Km) of the three cultivars. Thus, some replacement of NH4+ with NO3- could greatly improve the growth of rice plants, mainly on account of the increased uptake of NH4+ promoted by NO3-, and future studies should focus on the molecular mechanism of the increased uptake of NH4+ by NO3-. |
| Key Words: growth stages, N absorption and assimilation, nitrate, N uptake, rice |
| Citation: Duan, Y. H., Zhang, Y. L., Shen, Q. R. and Wang, S. W. 2006. Nitrate effect on rice growth and nitrogen absorption and assimilation at different growth stages. Pedosphere. 16(6): 707-717. |
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