Objective   Light responses of potato plants bearing colored tubers were studied.

  Method   Gas exchanges of potato leaves on 2 common varieties of yellow and white tubers and 4 of different colored tubers were determined. Collected data were fitted to the simulation models of rectangular hyperbola (RH), non-rectangular hyperbola (NRH), modified rectangular hyperbolic (MRH), and exponential function (EM). Photosynthetic parameters including maximum photosynthetic rate (P_n-max), light saturation point (LSP), light compensation point (LCP), dark respiration rate (R_d), and apparent quantum yield (AQY) on the plants were analyzed.

  Result  (1) All 4 models could adequately simulate the responses under low light, and RH, NRH, and EM failed to predict on photoinhibition. On the other hand, MRH accurately covered the entire light spectrum with a correlation coefficient (R²) greater than 0.99, as well as the smallest root mean square error and mean absolute error, among all models. (2) P_n-max of the colored potatoes were lower than those of the common varieties. They were 6.7%–34.2% lower than that of Favorita and 14.8%–40.0% than that of Minshu 1. Aside from Hongmei, the other 3 colored potatoes showed LSP below 1 000 μmol·m⁻²·s⁻¹, which was much less than those of the common varieties. No significant difference on the utilization under low light by the two categories of potatoes was observed. (3) Among the 4 colored varieties, Hongmei had the highest P_n-max and LSP, but lowest on the ability to use low light, while Mincaishu 3 exhibited the highest low light utilization. (4) The light response processes of stomatal conductance (G_s) and transpiration rate (T_r) were similar to that of net photosynthetic rate (P_n). They rose rapidly as the light intensity increased and then leveled off or declined. In contrast, the intercellular CO₂ concentration (C_i) showed a sharp decline before stabilization.

  Conclusion  The P_n-max and LSP of potato varieties that bore colored tubers were significantly lower than those of the common varieties indicating a lower photosynthetic potential and apparent photoinhibition. The information might lead to improved breeding and cultivation practices of colored potatoes.