Abstract
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.
Highlights
The Goodyerinae, one of the eight Cranichideae subtribes (Orchidoideae, Orchidaceae), is characterised by terrestrial herbs with fleshy roots either clustered or scattered along a rhizome and leaves usually arranged in a basal rosette
Species of Goodyerinae are described with similar anatomy to other taxa of Cranichideae, some anatomical characteristics appear to be specific to the subtribe
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
Summary
The Goodyerinae, one of the eight Cranichideae subtribes (Orchidoideae, Orchidaceae), is characterised by terrestrial herbs with fleshy roots either clustered or scattered along a rhizome and leaves usually arranged in a basal rosette. Aspidogyne (18 spp.) and Microchilus (19 spp.), are recorded in Brazil and are found in the phytogeographic domains of the Atlantic rainforest, Amazon rainforest and Cerrado biomes (Brazilian Neotropical Savannah) (BFG 2015; Meneguzzo 2012; Smidt et al 2016), in addition to the Asian introduced species Zeuxine strateumatica (Menini-Neto et al 2011; Engels et al 2016). This group of humicolous herbs grows in humid cloud forests. The species are morphologically characterised by their distinctive erect leafy stem and a less-developed horizontal, root bearing portion of the stem (Engels et al 2016) or rhizome (Pridgeon et al 2003) (Fig. 1)
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