Root morphology, histology and chemistry of nine fern species (pteridophyta) in a temperate forest

The variability patterns of fern root characteristics have seldom been studied. Here we explored variability in root morphology, histology and chemistry among fern species of temperate forest, and compared the observed patterns with those of seed plants. We sampled nine herbaceous fern species from temperate forest in northeastern China, and measured root morphological, histological and chemical characteristics across branch orders for each species. All nine fern species had 3 or 4 root orders. With increasing root order, diameter, tissue density, cortical thickness and vascular cylinder diameter increased, while specific root length (SRL) and tissue nitrogen concentration decreased. These were similar to the variability patterns that have been reported for seed plants, except for cortex. Like seed plants, nine fern species showed close relationships among root morphological, histological and chemical characteristics in first-order roots, such as diameter and cortex, tissue density and nitrogen concentration, suggesting that the general linkage between root structure and function exists in all vascular plants. The observed variation within fern root systems is comparable to the reported variation in seed plants, indicating that the same functional constraints control the evolution and development of root systems in vascular plants belonging either to the fern or seed plant lineages.