Abstract
Previously we reported cell-specific anthocyanin expression patterns that originated at stomatal complexes in the abaxial leaf epidermis. We showed that anthocyanin distribution patterns are a common phenomenon in higher plants. In addition, we have observed that expression patterns of peroxidase showed a similar pattern. These results suggested that anthocyanins work as antioxidants in vivo. In this study, we conducted pH fluorescence imaging studies to test for a similar pattern of stomatal complex-based distribution in cellular pH. For pH imaging, HPTS (8-Hydroxypyrene-1,3,6-Trisulfonate), a pH-dependent fluorescence reagent was used. Because of its high water solubility, non-toxicity, and high quantum yield, the reagent is suitable for living cells. In addition, HPTS has a dual-excitation and a single emission, the ratiometric method can be applied for quantitative determination of pH change. Our pH imaging on leaf epidermis revealed cell-specific pH differences that originated at stomatal complexes, similar to that observed for anthocyanin and peroxidase distribution. We discuss these results in the context of anthocyanin and pH patterns within leaf epidermal cells.
