Photosynthesis capacity and chlorophyll fluorescence characteristics of the Isodon rubescens (Hemsley) H. Hara stem

The biomass of Isodon rubescens stems is greater than that of the leaves. The stems possess a considerable surface area, although less than that of the leaves. The photosynthetic rates, light response curves and chlorophyll fluorescence characteristics of the stems were determined in this study to clarify their photosynthetic capacity and photosynthetic potential. The results showed that the I. rubescens stems possessed considerable photosynthetic capacity, although less than that of the leaves. The shape of the light response curve of the I. rubescens stem was different from that of leaf. The light response curve of stems slowly increased during the intermediate growth period. The light saturation point of the stems was significantly greater than that of the leaves. There was clear, strong light suppression in both stems and leaves. However, I. rubescens stems could effectively photosynthesize, and the stem has a high light saturation point and can adapt to intense light.