Leaf anthocyanin content changes in Zea mays L-grown at low temperature:: Significance for the relationship between the quantum yield of PSII and the apparent quantum yield of CO2 assimilation

The quantum yield of non-cyclic electron transport from PS II (Phi PS II) and the apparent quantum yield of CO2 fixation (Phi CO2) were measured in the maize genotype, R-CH HOPI, which shows a high leaf anthocyanin content when grown at a temperature slightly below 20 degrees C. Thus, the leaf anthocyanin content was thirty-five times higher in plants grown at 18 degrees C when compared to plants grown at 23 degrees C. The relationship between Phi PS II and Phi CO2 obtained at different CO2 partial pressure was linear for plants with both high and low leaf anthocyanin content. The Phi PS II/Phi CO2 ratio was about 16 in plants with high leaf anthocyanin content and about 10 in plants with low leaf anthocyanin content. The leaf light absorptance in the 400-700 nm region was higher in plants with higher leaf anthocyanin content. Since leaf absorptance between 400 and 600 nm and leaf anthocyanin content also resulted in a strict linear relationship, an indirect estimation of the absorbed light by leaf anthocyanins and thus at chloroplasts was derived. Using the correct estimation of the absorbed light at chloroplasts, to obtain Phi CO2, differences in Phi PS II/Phi CO2 ratios between plants with different leaf anthocyanin content were eliminated. The modulation of leaf anthocyanin content by growth temperature is regarded as an effective strategy to modulate the light available at the chloroplasts.