Anatomical and morphological leaf traits of three evergreen ferns (Polystichum setiferum, Polypodium interjectum and Asplenium scolopendrium)

Leaf mass per area (LMA) is one of the key features that correlates with the ecological performance both of seed plants and ferns. For ferns LMA is at the lower end of the range for seed plants and increases with leaf longevity. Data concerning morphological and anatomical traits of ferns and their relationship with LMA are quite limited. The objectives of this study were to (1) break down LMA into anatomical components; and (2) analyze the trade-offs between anatomical and morphological leaf traits, which determine LMA variations for three evergreen ferns. Seven morphological and 16 anatomical leaf traits of Polystichum setiferum, Polypodium interjectum and Asplenium scolopendrium growing outdoors in the Botanical Garden of Rome were analyzed using light microscopy. LMA was not significantly different between the considered species (4.55±0.55, 4.34±0.47, 4.28±0.41 mg cm-2 respectively) and it was in the range of other evergreen fern species. The morphological and anatomical structure of all species was significantly different and reflected environmental adaptation of species to their natural habitats. In particular, total lamina thickness was163±16.1 μm (P. setiferum), 244±33.7 μm (P. interjectum) and 336±32.2 μm (A. scolopendrium); leaf tissues density ranged from 127±16.9 mg cm-3 (A. scolopendrium) to 277±37.1 mg cm-3 (P. setiferum); intercellular air space varied between 23.2±2.07% (P. interjectum) and 41.8±1.61% (A. scolopendrium). The overall results highlight that LMA is an integral feature that can be obtained by different anatomical structure.