北方粳稻光合速率、气孔导度对光强和CO2浓度的响应

 以东北地区主栽的粳稻（Oryza sativa var. japonica）品种为对象，用美国LI-cor公司生产的Li 6400光合作用测定仪控制光强、CO2浓度和温度等环境条件，阐述了光合作用和气孔导度对光和CO2浓度的响应特征及其耦合关系。结果表明，光合速率随光强或CO2浓度的提高而增大，均遵循米氏响应；在不同CO2浓度下，表观量子效率随CO2浓度的提高而增大，但CO2浓度达到800 μmol•mol－1以上时，表观量子效率有所减小；在不同光强下，表观羧化效率也随光的增强而增大，但光强达到1 600 μmol•m-2•s-1以上时，表观羧化效率也有所减小；在光强和CO2浓度协同作用下，光合速率的响应遵循双底物的米氏方程，在光强和CO2浓度均趋于饱和时，北方粳稻（品种：辽粳294）剑叶的潜在最大光合速率为71.737 8 μmol•m-2•s-1，表观量子效率为0.056 0 μmolCO2•μmol-1 photons，表观羧化效率为0.103 1 μmol•m-2•s-1/μmol•mol－1。气孔导度也随光的增强而增大，对光强的响应规律也可以用Michaelis-Menten曲线模拟，而叶面CO2浓度的提高会使气孔导度减小，气孔导度（Gs）对叶面CO2浓度（Cs）的响应可以用Gs=Gmax,c/(1+Cs/Cs0)的双曲线方程模拟。在光强(PFD)和CO2浓度协同作用下，气孔导度可以用式Gs=Gmax(PFD/PFDc)/［(1+PFD/PFDc)(1+Cs/Cs0)］+Gct估算，当CO2浓度趋于0而光强趋于饱和时，北方粳稻的潜在最大气孔导度（Gmax）为0.670 9 mol•m-2•s-1。在光强和CO2浓度协同作用下，Ball-Berry模型及其修正形式依然能很好地表达气孔导度-光合速率的耦合关系，并且用叶面饱和水汽压差（Ds）修正耦合关系中的相对湿度可以提高模拟精度。

RESPONSE OF PHOTOSYNTHETIC RATE AND STOMATAL CONDUCTANCE OF RICE TO LIGHT INTENSITY AND CO2 CONCENTRATION IN NORTHERN CHINA

The response of photosynthetic rate and stomatal conductance of rice (Oryza sativa var. Japonica) to changes in light intensity and CO2 concentrations was studied using a Li-6400 in Northern China. In general, photosynthetic rates increased with light intensity and CO2 concentrations and could be expressed by a Michaelis-Menten function. Apparent quantum yield increased with CO2 concentrations but decreased slightly when CO2 concentrations exceeded 800 mol•mol-1. Similarly, apparent carboxylation efficiency increased with light intensity but decreased slightly when light intensity exceeded 1 600 mol•m-2•s-1. The response of stomatal conductance to light intensity can also be expressed by a Michaelis-Menten function, whereas the response to CO2 concentrations can be expressed by a hyperbola. If the combined effects of light intensity and CO2 concentrations are considered, the photosynthetic rate can be estimated by a Michaelis-Menten equation with a maximum photosynthetic rate of 71.74 mol•m-2•s-1. Apparent quantum yield was 0.056 0 mol CO2•mol-1 photons and carboxylation rate was 0.1031 mol•m-2•s-1/mol•mol-1. The response of stomatal conductance (Gsw) to light intensity can be expressed by a Michaelis-Menten function too, but the response to CO2 concentrations (Cs) can be simulated by the equation: Gsw=Gmax,c/(1+Cs/Cs0) where Gmax,c is maximum stomatal conductance of stomatal response to CO2 under a defined light intensity and Cs0 is a constant, because the stomatal conductance decreases with increases in CO2 concentrations, stomatal conductance can be estimated by Gsw=Gmax(PFD/PFDc)/［(1+PFD/PFDc)(1+Cs/Cs0)］+Gct in response to the combined effects of CO2 concentration and light intensity (I). The potential maximum stomatal conductance, Gmax, can reach 0.670 9 mol•m-2•s-1 under saturated light levels and CO2 near 0 mol•mol-1. Ball-Berry model and its revised form can still be used to express the coupled relationship of stomatal conductance and photosynthesis. The simulation precision will be improved if saturation vapor pressure deficit, Ds, at the leaf surface was used in the Ball-Berry model instead of relative humidity.