Living in the shadows: Gastrodia orchids lack functional leaves and open flowers

Abstract

Non‐photosynthetic plants dependent on fungi have long fascinated botanists and mycologists. The genus Gastrodia (Orchidaceae) contains more than 100 achlorophyllous species, including some species recently discovered in Japan and Taiwan which produce only closed self‐pollinating flowers. To date, Gastrodia is probably the only genus containing species with only closed flowers, which has been verified by a decade of monitoring hundreds of individuals. Here, the unique characteristics of the genus Gastrodia have been reviewed, emphasizing the reproductive biology of these newly described species that neither photosynthesize nor bloom. Investigation of such species that scarcely resemble other plants may paradoxically enhance our understanding of plants more broadly.

Transcriptomic heterochrony and completely cleistogamous flower development in the mycoheterotrophic orchid Gastrodia

“…By contrast, complete cleistogamy – the production of entirely cleistogamous flowers – may be risky, because plants with complete cleistogamous flowers are more likely to accumulate deleterious mutations and slow down their rate of adaptation, owing to the lack of outcrossing (Culley & Klooster, 2007; Pannell, 2009). Darwin (1877) doubted the reports of complete cleistogamy, recommending further study under natural conditions to verify that no chasmogamous flowers are ever produced; however, complete cleistogamy has now been recognized in some species (Culley & Klooster, 2007; Suetsugu, 2022).…”

Resurrection and emended description of Gastrodia foetida (Orchidaceae)

“…This notion is also based on the biological species concept, which defines a species as members of populations potentially interbreeding in nature because the completely cleistogamous status of G. takeshimensis blocks gene flow with its sympatric species G. foetida (Suetsugu 2022;Suetsugu et al 2023). Notably, G. foetida and G. nipponica are also reproductively isolated by their disjunct distribution (Fig.…”

“…Gastrodia Brown (1810: 330;Gastrodieae, Epidendroideae) is a mycoheterotrophic orchid genus across a large geographical area that includes Asia, Oceania, Madagascar, and Africa (Cribb et al 2010;Suetsugu 2022). The key characteristic of Gastrodia species includes fleshy tubers, absence of normal leaves, united sepals and petals, and two mealy pollinia without caudicles (Cribb et al 2010;Hsu & Kuo 2010;Hsu et al 2012;Suetsugu 2021Suetsugu , 2022. However, the genus Gastrodia has been a source of systematic confusion due to its wide distribution, phenotypic plasticity, convergent morphological features, and short flowering duration (Suetsugu et al 2018).…”

“…Despite these limitations, several recent studies have reported many new Gastrodia species (Ong & O'Byrne 2012;Tan et al 2012;Hsu et al 2016;Pelser et al 2016;Tsukaya & Hidayat 2016;Metusala & Supriatna 2017;Aung & Jin 2018;Ma et al 2019;Suetsugu 2019Suetsugu , 2021Bandara et al 2020). Consequently, the genus comprises more than 100 species, making it the most species-rich mycoheterotrophic genus (Suetsugu 2022). However, more extensive taxonomic studies will be required to precisely characterize the diversity of this group, for which the precise identification of individual species remains problematic.…”

“…1B). Intriguingly, several new taxa within the G. nipponica species complex have been described in recent years (Hsu & Kuo 2010;Suetsugu 2013Suetsugu , 2014Suetsugu , 2016Suetsugu , 2017Suetsugu , 2021, and the G. nipponica species complex is now recognized as an ideal model for understanding speciation and diversification of mycoheterotrophic plants (Kishikawa et al 2019;Ogaki et al 2019;Suetsugu 2022;Suetsugu et al 2023). Therefore, although a relatively long, narrow perianth tube (ca.…”