Root and leaf anatomy of some terrestrial representatives of the Cranichideae tribe (Orchidaceae)

Abstract

The Orquidaceae family has more than 25,000 species, of which 20 % are terrestrial Cranichideae mainly belonging to the tribe, which is inserted in Orchidoideae, one of the five subfamilies of the Orchidaceae. This group of terrestrial orchids presents a confusing taxonomy and is a poorly known group in terms of their vegetative anatomy in opposition to the epiphytic representatives that have been extensively investigated. This paper describes the root and leaf anatomy of ten species of Cranichideae tribe found in Brazil, belonging to subtribes Cranichidinae, Goodyerinae, and Spiranthinae, comparing their organization to those of the epiphytic plants. We also point out some features that can be useful for the characterization of each subtribe. The roots have studied characteristics that may assist in the absorption and retention of water as the occurrence of velamen and exodermis system, and in the presence of tilossomos Cranichidinae and Spiranthinae. The leaves are narrow with a homogeneous mesophyll, covered by uniseriate epidermis and covered by thin cuticle. The xylem cells are arranged in pairs or inverted V-shape, as in the other orchids Cranichideae tribe.

Anatomy and Histochemistry of the Vegetative System of Brachystele guayanensis (Lindl.) Schltr. (Orchidaceae), a Potential Medicinal Species

“…The cells of the exodermis are slightly thickened (Figure 4b,c) and the endodermis cells have evident Casparian strips (Figure 4k). Similar patterns can be observed in other terrestrial orchids, particularly in the subfamily Orchidoideae, such as in Orchideae [27] and Cranichideae [16,20,21].…”

“…The cortex of B. guayanensis is surrounded by a fiber ring (Figure 3a,b,h) and consists of 16-22 layers of rounded parenchyma cells of varying sizes (Figure 3a,b) with small triangular intercellular spaces. Some of the parenchyma cells contain raphides (Figure 3e) and tiny starch grains enveloped by two limiting membranes and gathered in spiranthosomes (Figure 3f)-spherical specialized amyloplasts found in Cranichideae and interpreted as a synapomorphy of the tribe and are associated with nutrients storage [16,20,32]. While it is not entirely clear, some authors [33,34] attribute the polyhedral form of spiranthosomes to intracellular density.…”

“…by Bona et al [16]. According to Stern et al [8], Andreota et al [20], and Bernal et al [15], simple trichomes provide better attachment to the substrate and increase contact with that surface, thereby facilitating the absorption of water and mineral salts.…”

Anatomy and Histochemistry of the Vegetative Organs of Brachystele guayanensis (Lindl.) Schltr. (Orchidaceae), a Potential Medicinal Species

“…Ormerod and Zeuxine strateumatica (L.) Schltr.) by Andreota et al [17] and Bona et al [20] and described for Aa paleacea (Kunth) Rchb. f. and Pterichis multiflora (Lindl.)…”

“…Anatomical descriptions of the vegetative organs of Orchidoideae Lindl., the subfamily in which Brachystele is included, are still incipient and have mainly focused on species not occurring in Brazil [e.g., [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Anatomical studies of Brachystele are currently limited to the work of Bernal et al [18], who examined the root trichomes of representatives of Spiranthinae Lindl.…”