Quantifying light response of photosynthesis: addressing the long-standing limitations of non-rectangular hyperbolic model

Light intensity (I) fluctuates rapidly and is the most important environmental factor affecting photosynthesis. Accurate characterization of light-response curve of leaf-scale photosynthesis (P-N-I curve) is fundamental for understanding P-N-I relations at the whole-plant and ecosystem scales. A robust P-N-I model should be accurate in reproducing P-N-I curves over light-limited, light-saturated, and photoinhibitory I levels, and ideally returning key quantitative traits defining the curves, including initial slope of increase (alpha), dark respiration rate (R-D), the maximum net photosynthetic rate (P-Nmax), and the corresponding saturation intensity (I-sat). We need to improve a model reproduction of (1) P-N-I responses over low I levels and (2) the widely reported decline of P-N at photoinhibitory I levels. Our observation-modelling comparison, shown by the widely used non-rectangular hyperbolic model, led to (1) underestimation of RD, (2) overestimation of P-Nmax, and (3) failure in reproducing the photoinhibitory response when I surpassed the cultivar-specific I-sat. In contrast, our model addressed the above limitations extremely well. The results highlighted the accuracy and robustness of our model, especially in (1) returning key traits defining the curve and (2) reproducing the curve over both low [i.e., 0-50 mu mol(photon) m(-2) s(-1)] and photoinhibitory I levels (i.e., beyond I-sat).

Automated summary

The intensity of light has a significant impact on photosynthesis. Developing an accurate P-N-I model is crucial for understanding the relationship between light, photosynthesis, and plant growth. Current research shows the need for improvement in modeling low light and photoinhibitory conditions.