Structure and Development of Flowers and Inflorescences in Burmannia (Burmanniaceae, Dioscoreales)

Species of the genus Burmannia possess distinctive and highly elaborated flowers with prominent floral tubes that often bear large longitudinal wings. Complicated floral structure of Burmannia hampers understanding its floral evolutionary morphology and biology of the genus. In addition, information on structural features believed to be taxonomically important is lacking for some species. Here we provide an investigation of flowers and inflorescences of Burmannia based on a comprehensive sampling that included eight species with various lifestyles (autotrophic, partially mycoheterotrophic and mycoheterotrophic). We describe the diversity of inflorescence architecture in the genus: a basic (most likely, ancestral) inflorescence type is a thyrsoid comprising two cincinni, which is transformed into a botryoid in some species via reduction of the lateral cymes to single flowers. Burmannia oblonga differs from all the other studied species in having an adaxial (vs. transversal) floral prophyll. For the first time, we describe in detail early floral development in Burmannia. We report presence of the inner tepal lobes in B. oblonga, a species with reportedly absent inner tepals; the growth of the inner tepal lobes is arrested after the middle stage of floral development of this species, and therefore they are undetectable in a mature flower. Floral vasculature in Burmannia varies to reflect the variation of the size of the inner tepal lobes; in B. oblonga with the most reduced inner tepals their vascular supply is completely lost. The gynoecium consists of synascidiate, symplicate, and asymplicate zones. The symplicate zone is secondarily trilocular (except for its distal portion in some of the species) without visible traces of postgenital fusion, which prevented earlier researchers to correctly identify the zones within a definitive ovary. The placentas occupy the entire symplicate zone and a short distal portion of the synascidiate zone. Finally, we revealed an unexpected diversity of stamen-style interactions in Burmannia. In all species studied, the stamens are tightly arranged around the common style to occlude the flower entrance. However, in some species the stamens are free from the common style, whereas in the others the stamen connectives are postgenitally fused with the common style, which results in formation of a gynostegium

Comparative analysis of plastid genomes in the non-photosynthetic genus Thismia reveals ongoing gene set reduction

Heterotrophic plants provide intriguing examples of reductive evolution. This is especially evident in the reduction of their plastid genomes, which can potentially proceed toward complete genome loss. Several milestones at the beginning of this path of degradation have been described; however, little is known about the latest stages of plastome reduction. Here we analyze a diversity of plastid genomes in a set of closely related non-photosynthetic plants. We demonstrate how a gradual loss of genes shapes the miniaturized plastomes of these plants. The subject of our study, the genus Thismia, represents the mycoheterotrophic monocot family Thismiaceae, a group that may have experienced a very ancient (60–80 mya) transition to heterotrophy. In all 18 species examined, the plastome is reduced to 14–18 kb and is highly AT-biased. The most complete observed gene set includes accD, seven ribosomal protein genes, three rRNA, and two tRNA genes. Different clades of Thismia have undergone further gene loss (complete absence or pseudogenization) compared to this set: in particular, we report two independent losses of rps2 and rps18

Burmannia championii Thwaites 1864

1. Burmannia championii Thwaites (1864: 325) MT Vietnam (Dang et al. 2015)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 66, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia wallichii Hooker

15. Burmannia wallichii (Miers) Hooker f. (1888: 666) MT ≡ Gonianthes wallichii Miers (1841: 537) Cambodia (Cho et al. 2016) Laos (Newman et al. 2007a, 2007b) Vietnam (Gagnepain 1908, Jonker 1938, Pham-Hoang 2000, Nguyen et al. 2003)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 67, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia disticha Linnaeus 1753

6. Burmannia disticha Linnaeus (1753: 287) AT Cambodia (Gagnepain 1908, Cho et al. 2016) Laos (Gagnepain 1908, Newman et al. 2007a) Vietnam (Gagnepain 1908, Jonker 1938, Pham-Hoang 2000, Nguyen et al. 2003)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 66, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia cochinchinensis Gagnepain 1907

3. Burmannia cochinchinensis Gagnepain (1907: 463) PMT Vietnam (type location)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 66, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia subcoelestis Gagnepain 1907

13. Burmannia subcoelestis Gagnepain (1907: 464) PMT Cambodia (Gagnepain 1908, Cho et al. 2016) Laos (type location) Vietnam (Pham-Hoang 2000, Nguyen et al. 2003) Presence of B. subcoelestis in Cambodia is questionable: Gagnepain (1908) and Cho et al. (2016) listed the species for Cambodia without indicating any specimens or locations, whereas Zhang (1999) cited specimens of B. subcoelestis only from Laos and Vietnam.Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 67, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia itoana Makino 1913

7. Burmannia itoana Makino (1913: 1) MT Vietnam (this study)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 66, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia oblonga Ridley 1904

11. Burmannia oblonga Ridley (1904: 33) MT = Burmannia bifida Gagnepain (1907: 462) Cambodia (Gagnepain 1907, 1908, Cho et al. 2016) Vietnam (Gagnepain 1907, 1908, Jonker 1938, Pham-Hoang 2000, Nguyen et al. 2003)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 67, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141

Burmannia coelestis D. Don 1825

5. Burmannia coelestis D. Don (1825: 44) PMT Cambodia (Gagnepain 1908, Zhang & Saunders 2000, Cho et al. 2016) Laos (Gagnepain 1908, Zhang & Saunders 2000, Newman et al. 2007a) Vietnam (Gagnepain 1908, Jonker 1938, Pham-Hoang 2000, Zhang & Saunders 2000, Nguyen et al. 2003)Published as part of Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, pp. 61-70 in Phytotaxa 544 (1) on page 66, DOI: 10.11646/phytotaxa.544.1.5, http://zenodo.org/record/650141