Studies of petiolar anatomy in ferns: structural diversity and systematic significance of the circumendodermal band

Abstract

In ferns, leaf traces in the petioles are sometimes surrounded by a circumendodermal band (CB), a cell layer of varying structure and arrangement. We studied the CB of 89 fern species from 53 genera and 28 families, and its correlation with leaf trace configuration, leaf dissection and life form, to explore its anatomical diversity, possible origin and suitability for fern systematics. The cells of the CB always contain tannins in their lumina and their walls, but lack lignin and suberin. Cell wall thickness varies among species and may prove to be useful for fern systematics. The occurrence of the CB correlates with a larger number of vascular strands in the leaf trace and a lower degree of leaf dissection, but not with life form. Cystopteridaceae is the earliest branching family with a CB. The exclusive presence of the CB in nine of the most derived fern families supports the hypothesis of a single origin before the divergence of the two major clades of eupolypods. The discontinuity or absence of the CB in some species of derived families (e.g. Polypodiaceae, subfamily Polypodioideae) is interpreted as a secondary loss. Possible functions of the CB are discussed. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 596–610.

The Structure and Function of Xylem in Seed-Free Vascular Plants: An Evolutionary Perspective

“…In a phylogenetically extended survey, Hernandez-Hernandez et al ( 2012 ) indicated an increased presence of the circumendodermal band in more derived ferns. Resembling a thick casparian strip, this band encapsulates the xylem and phloem tissues ( Fig.…”

“…A number of hypotheses have been proposed to explain the presence of this structure. For example, this waxy layer may increase frond structural rigidity (Hernandez-Hernandez et al 2012 ), an important trait in many epiphytes in which fronds are displayed at steep angles and vulnerable to damage by falling canopy debris. Epiphytic ferns may also be capable of foliar water absorption, so biomechanical needs may trump xylem-mediated water transport in humid habitats.…”

Foliar epidermal micromorphology and its taxonomic implications in some selected species of Athyriaceae

“…According to the study of Kato () on Athyriaceae, the vascular structures of rhizomes, stipes and rachis of Athyrium, Diplazium and their relatives are very similar to those of Acystopteris, Gymnocarpium, onoclea and Woodsia . Beside these treachery elements is used for taxonomic purpose in this family (Xu & Wang, ) stomata types (Yan‐Ping & Jian‐Meng, ) vascular bundles (Karafit, Rothwell, Stockey, & Nishida, ) and the petiole anatomy (Hernandez‐Hernandez, Terrazas, Mehltreter, & Angeles, ) have been used for the taxonomic purpose in Athyriaceae. However, on the basis of morphological and few earlier anatomical studies the grouping of the taxa looks very artificial some of the phylogenetic studies were performed which can possibly help in the delimitation of genera and species within Athyriaceae (Chunxiang, Shugang, Xiaoyan, & Qun, ; Liu et al, ; Sano et al, ; Wang, Xie, & Zhao, ; Wei et al, ).…”

Estudio morfo-anatómico comparado en pecíolos de las especies de Asplenium (Aspleniaceae) de Argentina

“…La banda circumendodermal (BC), ubicada en la zona más interna de la corteza de los pecíolos, es característica de varias familias de helechos (Hernández-Hernández et al, 2012). Esta consiste en células con paredes engrosadas no lignificadas (compuestas de celulosa y taninos), con el mismo origen que la endodermis pero sin depósitos de suberina ni lignina.…”