Comparative vegetative anatomy of Neotropical Goodyerinae Klotzsch (Orchidaceae Juss.: Orchidoideae Lindl.)

Abstract

The Neotropical genera Aspidogyne and Microchilus (Goodyerinae, Cranichideae, Orchidaceae) comprise ca. 200 rainforests terrestrial species. Although species of Goodyerinae are described with similar anatomy to other taxa of Cranichideae, some anatomical characteristics appear to be specific to the subtribe. Our goal was to characterise the anatomical structure of the vegetative organs of Aspidogyne and Microchilus to identify specific characters of Goodyerinae. Root, stem and leaf samples from eleven species were analysed using light and scanning electron microscopy. The leaves are hypostomatic and glabrous with predominantly anisocytic or tetracytic stomata, thin cuticle, homogeneous mesophyll with chromoplast and raphides, and collateral vascular bundles with parenchyma sheath and collenchyma in the midrib. Spiranthosomes were cofirmed for all species and some specific characteristics were identified in the root, such as the presence of collenchyma in both the cortex and the stele, vascular tissue with fibre-tracheids in the centre of the vascular cylinder, and the presence of a true endodermis with Casparian strips in the stem. Therefore, the root and stem were the organs that showed more taxon-specific characteristics for Goodyerinae, which can be used to better delimited the subtribe.

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 arrangement of the fundamental tissue is similar to that described by Stern [8] and by Stern and Judd [36,37] for the aerial stems of other Orchidaceae groups (such as Vanilloideae [36,37]; Orchidoideae, tribes Diseae Dressler and Orchideae Small; and Epidendroideae Lindl., tribes Sobralieae Pfitzer and Triphoreae Dressler [8,38]), as well as other groups of Monocotyledons [39]. Although the endodermis (with Casparian strips) and/or pericycle are not very distinct, unlike other Cranichideae [8,16] as described here (Figure 3b), they may participate in the genesis of adventitious roots and therefore exhibit meristematic activity [39]. The arrangement of the fundamental tissue is similar to that described by Stern [8] and by Stern and Judd [36,37] for the aerial stems of other Orchidaceae groups (such as Vanilloideae [36,37]; Orchidoideae, tribes Diseae Dressler and Orchideae Small; and Epidendroideae Lindl., tribes Sobralieae Pfitzer and Triphoreae Dressler [8,38]), as well as other groups of Monocotyledons [39].…”

“…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 Andreota et al [20]; and for 11 species of Aspidogyne Garay and Microchilus C. Presl. 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.…”

“…Plants 2023, 12, 2635 2 of 16 In anatomical terms, Orchidoideae is poorly studied since most of the species sampled in previous studies [8,10] occur outside the neotropical region-one of its centers of diversity-where many of its species are endemic [1,2] and are subject to conditions and environmental factors that differ from other parts of the world. Although the phytochemistry of some species is relatively known, especially those occurring in the Old World [5,7,11], they are used in the treatment of various diseases because they have compounds with biological activities (e.g., anti-inflammatory, anti-Hepatitis B, neuroprotective, anti-tumor, antioxidant, among others), thus highlighting their potential as medicinal plants.…”