Relationship between metal and pigment concentrations in the Fe-hyperaccumulator moss Scopelophila ligulata.

Scopelophila ligulata is known to be a Fe-hyperaccumulator moss; however, its mechanism of accumulation and the effects of Fe on pigments remain unclear. To clarify the effects, we measured its metal and pigment concentrations. The Fe concentration in S. ligulata was 10-61 times higher than that in normal mosses, confirming that the moss is a Fe-hyperaccumulator. The black samples of S. ligulata had the highest Fe concentration (2.9 wt%) and the second in the order of decreasing Fe concentration (2.2 wt%), which explains their color and indicates that the excess amount of Fe is distributed through the plant body. Moreover, we observed that the concentration of Ca is negatively correlated with the concentrations of pigments and, conversely, that the concentration of K is positively correlated with the concentrations of pigments. This inverse relationship between Ca and K can be explained by the reduced uptake of K in S. ligulata in response to Ca stress, which is supported by the fact that the concentration of Ca is negatively correlated with that of K. These findings provide a better understanding of the relationships between metals and pigments in the Fe-hyperaccumulator moss S. ligulata.