Leaf optical properties and photosynthesis of fern species with wide range of divergence time in relation to the mesophyll anatomy.

We obtained a strong coordination among the light capture, mesophyll anatomy, and photosynthesis rate in fern species for the first time. The thick mesophyll of the ferns of a newer divergence time does not necessarily relate to the high photosynthetic capacity on a leaf-area-basis. Rather, the thick mesophyll that is accompanied by thick cell walls allowed the ferns to adapt to wider environments through increasing the leaf toughness, which would contribute to the diversification of fern species.