Abstract: A comparative study was conducted on the photosynthetic characteristics of seven peppers with different purple levels with CS3 hybrid F2 generation segregation population. The seven peppers were named as Z-1，Z-2，Z-3，Z-4，Z-5，Z-6 and Z-7，respectively，as the color changed from dark purple to green. Four models（i.e.，rectangular hyperbolic model，non-rectangular hyperbolic model，exponential model and modified rectangular hyperbolic model）were adopted to fit the light response curves for photosynthesis of the seven peppers. The difference among the four models was determined by comparing the parameters，such as determining coefficient（R2），apparent quantum efficiency（α），maximum net photosynthetic rate（Pn,max），light compensation point（LCP），light saturation point（LSP）and dark respiration rate（Rd）. The light response curves among the 7 types of peppers were significantly different under high photosynthetic effective radiation（PAR），i.e.，the light response of net photosynthetic rate（Pn） for the peppers with higher purple levels remained rising after PAR greater than 1 200 μmol · m-2 · s-1，without saturation and light inhibition phenomena. Meanwhile，stomata conductance（Gs）and transpiration rate（Tr）increased rapidly，the inter-cellular CO2 concentration（Ci）and water use efficiency kept in a high level. Under the photosynthetic effective radiation of 2 000 μmol · m-2 · s-1，the highest Pn value was （20.16 ± 0.58）μmol · m-2 · s-1 for Z-4，while the highest water use efficiency value（CO2/H2O）was（2.02 ± 0.01）μmol · μmol-1 for Z-5. Four models were applicable to fitting the Pn–PAR curve of multiple peppers varying in purple degree，with the R2 between 0.964 and 1.000. According to R2，the model performance decreased in the order of modified rectangular hyperbolic model，non-rectangular hyperbolic model，rectangular hyperbolic model and exponential function model. Nevertheless，the light saturation point（LSP）was only obtained by the modified rectangular hyperbolic model for the five types of purple peppers，i.e.，Z-2，Z-4，Z-5，Z-6 and Z-7. The maximum values of LSP were found in Z-4 through the modified rectangular hyperbolic model，valued（2 958.41 ± 923.48）μmol · m-2 · s-1. Our findings suggested that（1）purple pepper has an excellent weak light utilization capability，and could well adapt to strong light conditions without saturation or light inhibition phenomenon. At the same time，purple pepper has a lower dark respiration，which in turn benefits organism matter accumulation.（2）Purple pepper like Z-5 facilitates the selection of water-saving material.（3）The modified rectangular hyperbolic model is more suitable for fitting the purple pepper Pn–PAR curve as it could provide more parameters comparable to the measured ones.

Key words: pepper, purple leaf, photosynthesis, light response curve, light response model, curve fitting