Chlorophyll Fluorescence Potential and Photosynthetic Capacity of Isodon rubescens Leaf back

The upper side of the Isodon rubescens leaf normally faces the sun. The back of the leaves occasionally face upwards because of wind, rain or animal activity. The light response curves, photosynthetic rates and rapid light curves of the chlorophyll fluorescence of the leaf back and front were analysed with a Li-6400 photosynthesis system analytical instrument and a PAM-2500 portable chlorophyll fluorescence instrument to study the photosynthetic capacity of the leaf back. The results evidenced that the leaf back possessed high photosynthetic capacity. In general, the apparent quantum yield and the light saturation point of the leaf back were respectively lower than that of the corresponding leaf front. The light compensation points of the leaf backs were slightly higher than that of the corresponding leaf fronts. The photosynthetic capacity of the leaf back was slightly lower than that of the corresponding leaf front at the same light intensity. I. rubescens can normally photosynthesize and grow when the leaf back is facing upward.