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Pak. J. Bot., 47(3): 877-882, 2015.

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ImproveD performance of photosynthetic light response equations with unified parameters for rice leaves with different SPAD values

Junzeng Xu^1,2*, Yanhua Wang ², Shihong Yang², Shizhang Peng¹ AND Weili Kong^2,3

Abstract: The rectangular hyperbola (RH), Mitscherlich (M) and YE equation were applied to describe the photosynthetic light response (PLR) curves measured from rice leaves with different SPAD values, to reveal the relationship between SPAD values and parameters in different equations, and to establish the modified PLR equations. The parameters in PLR equations are largely varied. SPAD value, as an indicator of leaf N contents, was highly correlated to the parameter of P_nmax in RH, M and YE equations. Incorporating the factor SPAD into PLR equations, the modified equations (MRH, MM, and MYE) were established which were feasible to describing the PLR curves for leaves with different SPAD values using the identical parameters for the ten PLR curves as a whole, and perform much better than the general PLR equations (GRH, GM, and GYE). It indicated that incorporating easy available indicators of leaf physiological and morphological traits in the PLR equations, such as SPAD as an indicator of leaf N or Chlorophyll contents, is an easy way to overcome the shortcoming of parameters variation in PLR equations between individuals of the same specie growing in different environments. Further validation should be done for different crops with both SPAD and other possible factors.

Key words: Photosynthetic light response equation, Photosynthesis, Leaf nitrogen content, SPAD, rice.

¹State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China

²College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China

³Quzhou Water Conservancy and Hydropower Investigation and Design Co., Ltd., Quzhou 324002, China

*Corresponding author e-mail: xjz481@hhu.edu.cn Tel.:  +86 25 83786016;