ORIGINAL RESEARCH Partial nitrate nutrition amends photosynthetic characteristics in rice (Oryza sativa L. var. japonica) differing in nitrogen use efﬁciency Yali Zhang • Huajun Lv • Dongsheng Wang • Jingchao Deng • Wenjing Song • Kousar Makeen • Qirong Shen • Guohua Xu Received: 17 December 2009 / Accepted: 27 August 2010 / Published online: 17 September 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Partial nitrate nutrition (PNN) was found to improve rice (Oryza sativa L. var. japonica) growth. How- ever, how PNN is related to photosynthesis in rice cultivars with different nitrogen use efﬁciency (NUE) is still not clear. Two rice cultivars, Nanguang (high NUE) and Elio (low NUE), were grown under sole NH 4 ? and PNN at a total nitrogen concentration of 2.86 mM. The dry weight, leaf area, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and gas exchange parameters were measured. Nitrogen and Rubisco contents in the newly expanded leaves of cv. Nanguang were similar to those of cv. Elio when only NH 4 ? was supplemented in the nutrient solution. However, in cv. Nanguang, nitrogen and Rubisco contents increased under PNN than under sole NH 4 ? nutrition. Higher nitrogen and Rubisco contents were recorded in cv. Nanguang than in cv. Elio under PNN. The ratio of carboxylation efﬁciency (CE) to Rubisco content in cv. Nanguang was 11 and 14% higher than that in cv. Elio under NH 4 ? and PNN, respec- tively. CE was 14% higher in cv. Nanguang than that in cv. Elio. The results suggest that PNN causes an increase in photosynthesis in cv. Nanguang. It is concluded that differ- ences in Rubisco activity, rather than stomatal limitation, are responsible for the differences in photosynthesis between the two cultivars. The presence of nitrate increases Rubisco content in rice with a high NUE, which leads to faster bio- mass accumulation at later growth stages. Keywords Carboxylation efﬁciency  Gas exchange parameter  Nitrogen  Partial nitrate nutrition  Rice  Rubisco  Stomatal limitation Abbreviations A CO 2 assimilation rate A max Maximum photosynthetic rate CE Carboxylation efﬁciency C i Intercellular CO 2 concentration C o Ambient CO 2 concentration g s Stomatal conductance g m Leaf mesophyll conductance K C Michaelis–Menten constants for CO 2 K O Michaelis–Menten constants for O 2 l Stomatal limitation NUE Nitrogen use efﬁciency O Partial pressure of O 2 PNN Partial nitrate nutrition PPFD Photosynthetic photon ﬂux density Tr Transpiration rate V cmax Maximum Rubisco carboxylation rate a Apparent quantum yield C * CO 2 compensation point without dark respiration Introduction Since nitrogen (N) is one of the essential macronutrients for rice growth, it is one of the main factors to be Y. Zhang (&)  H. Lv  D. Wang  J. Deng  W. Song  K. Makeen  Q. Shen  G. Xu College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095 Nanjing, China e-mail: ylzhang@njau.edu.cn Y. Zhang State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 21008 Nanjing, China D. Wang Vegetable Science Institute, 210042 Nanjing, China 123 Plant Growth Regul (2011) 63:235–242 DOI 10.1007/s10725-010-9520-7