A single leaf of Camellia oleifera has two types of carbon assimilation pathway, C3 and crassulacean acid metabolism

Abstract

C4 plants, whose first product of photosynthetic CO2 fixation is a four-carbon acid, have evolved independently many times. Crassulacean acid metabolism (CAM) is a biological mechanism known to exhibit some C4 characteristics such as the C3 cycle during daylight and demonstrates the C4 cycle at night. There are also various C3-CAM intermediates, whose CAM pathway can be induced by environmental changes. However, neither fungus-induced CAM nor Theaceae CAM have been reported previously. Here, we show that CAM could be generated by fungus infection in Camellia oleifera Abel. young leaves, even at a location of a single leaf where the upper part had been transformed into a succulent one, while the lower part remained unchanged. The early photosynthetic products of dark-grown C. oleifera succulent leaves were malate, whereas C. oleifera normal leaves and light-grown succulent leaves incorporated most of 14C into the primary photosynthetic product 3-phosphoglycerate. Camellia oleifera succulent leaves have a lower absolute δ13C value, much lower photorespiration rates and lower transpiration rates during the day than those of C. oleifera normal leaves. Like a typical CAM plant, stomata of C. oleifera succulent leaves closed during the daylight, but opened at night, and therefore had a detectable CO2 compensation point in darkness. Net photosynthetic rates (P n) fluctuated diurnally and similarly with stomatal aperture. No light intensity saturation could be defined for C. oleifera succulent leaves. C4 key enzymes in C. oleifera succulent leaves were increased at both the transcriptional/translational levels as well as at the enzyme activity level. © The Author 2011.