Nymphaea thermarum

Description

Vegetative characteristics

It is a diminutive, aquatic, rhizomatous herb with 1–2(–5) cm long rhizomes. The peltate, petiolate, glabrous, orbicular to suborbicular leaves have a 2.8–3.2 cm long, and 2.5–3 cm wide lamina. The lobes of the lamina are overlapping each other, or are almost parallel. The petiole is 4–6(–8) cm long.

Generative characteristics

The up to 2 cm wide, hermaphroditic, incompletely protogynous, white flowers have 1.5–3 cm long peduncles. The four green, lanceolate sepals with a round apex are 1.7–1.8 cm long, and 0.6–0.7 cm wide. The 6–8 white petals are 1.5–1.6 cm long, and 4 mm wide. The androecium consists of up to 16 stamens with a sterile apical appendage and they gradually decrease in size from the 9–10 mm long outer stamens to the 5–6 mm long inner stamens. The filament is up to 5–6 mm long, likewise, the connective is 5–6 mm long, and the anthers are 1.5–4 mm long. The gynoecium consists of 7–9 basally fused, 4–5 mm long carpels with a 2mm long, and 1 mm wide stigma forming a stigmatic disk. The up to 1.2–1.5 cm wide fruit bears hundreds of bright red to brown, arillate seeds.

Cytology

The diploid chromosome count is 2n = 28. The genome size is 498.78 Mb. The chloroplast genomes of Nymphaea thermarum and Nymphaea heudelotii are identical.

Taxonomy

Nymphaea thermarum was published by the German botanist Eberhard Fischer in 1988. The type specimen was collected by Fischer in hot springs South of Nyakabuye, Rwanda on the 25th of April 1987. Is is placed within the subgenus Nymphaea subg. Brachyceras.

Etymology

The specific epithet thermarum refers to the hot spring and temperature that provided its native habitat.

Breeding

They can self-pollinate, and after blooming the flower stalk bends so the fruit contacts the mud. The fruit contains 300 to 400 seeds. The sepals are slightly hairy, and as large as the flower's petals. The plant is a tropical day bloomer displaying protogynous flowering patterns, opening early in the morning on the first day with female floral functioning, closing in early afternoon, and opening on the second day with male functionality. It is in the Nymphaea subgenus Brachyceras, though the leaves are more typical of the subgenus Nymphaea. It apparently does not form tubers. Seeds are large for plants in subgenus Brachyceras. The lifespan of Nymphaea thermarum can be greater than 10 years.

Conservation

The plant's native habitat was damp mud formed by the overflow of a freshwater hot spring in Mashyuza, southwest Rwanda. It was thought to have become extinct in the wild around 2008, when local farmers began using the spring for agriculture. The farmers cut off the flow of the spring, which dried up the tiny area—just a few square metres—that was believed to be the entire habitat. Before the extinction of the first known population, Fischer sent some specimens to Bonn Botanic Gardens in Germany when he saw that their habitat was fragile. The plants were kept alive at the gardens, but botanists could not solve the problem of propagating them from seed.

The first published occurrence of N. thermarum germination was by Carlos Magdalena, at the Royal Botanical Gardens, Kew. By placing the seeds and seedlings into pots of loam surrounded by water of the same level in a 25 C environment, eight began to flourish and mature within weeks and in November 2009, the waterlilies flowered for the first time. During this time, a rat had eaten one of the last two cultivated plants in Germany. With the germination problem solved, Magdalena says that the tiny plants are easy to grow, giving it potential to be grown as a houseplant. In January 2014, a surviving water lily was stolen from the Royal Botanic Gardens. Botanic gardens have been criticised for not providing plant material to repatriate to Rwanda.

Uses

It has been proposed to be used as a model species for basal angiosperms, due to its small size, rapid lifecycle, and small genome. For instance, together with Nymphaea dimorpha it has been used to study seed evolution.

References

References

1. Abeli, T.. (2024). "''Nymphaea thermarum''".
2. "''Nymphaea thermarum'' Eb.Fisch.".
3. Ghosh, Pallab. (2010-05-18). "Waterlily saved from extinction". BBC News.
4. Magdalena, Carlos. (November 2009). "The world's tiniest waterlily doesn't grow in water!". Water Gardeners International.
5. Rwanda, National Herbarium of. "International Team of Botanists Rediscover Extinct Water Lily in Rwanda".
6. "''Nymphaea thermarum''". Royal Botanic Gardens, Kew.
7. (2010). "690. Nymphaea Thermarum". Curtis's Botanical Magazine.
8. Roestel, J. A., Wiersema, J. H., Jansen, R. K., Borsch, T., & Gruenstaeudl, M. (2024). [https://onlinelibrary.wiley.com/doi/pdf/10.1111/cla.12584 On the importance of sequence alignment inspections in plastid phylogenomics–an example from revisiting the relationships of the water‐lilies.] Cladistics.
9. (1988). "Beiträge zur Flora Zentralafrikas. I. Eine neue ''Nymphaea'' sowie ein neuer ''Streptocarpus'' aus Rwanda". Feddes Repertorium.
10. (2017). "Water lilies as emerging models for Darwin's abominable mystery". Horticulture Research.
11. (2022). "The complete chloroplast genome of ''Nymphaea thermarum'' (Nymphaeaceae) from Rwanda, Africa". Mitochondrial DNA Part B.
12. Fischer, Eberhard. (1993). "Taxonomic results of the BRYOTROP-Expedition to Zaire and Rwanda". Tropical Bryology.
13. Magdalena, Carlos. "Nymphaea thermarum". Kew Gardens.
14. (2018-03-14). "In Harvard studies of plant tug-of-war, mom wins".
15. (2015). "Floral biology and ovule and seed ontogeny of ''Nymphaea thermarum'', a water lily at the brink of extinction with potential as a model system for basal angiosperms". Annals of Botany.
16. Publishing, Bloomsbury. (2014-08-14). "Going, Going, Gone: 100 animals and plants on the verge of extinction". Bloomsbury Publishing.
17. (2010-05-19). "Smallest waterlily in the world saved from extinction – by Kew Gardens".
18. McCarthy, Michael. (2010-05-19). "Smallest lily saved from extinction". [[The Independent]].
19. [http://www.australiangeographic.com.au/journal/extinct-waterlily-back-from-the-dead.htm/ "'Extinct' Waterlily back from the dead"] {{webarchive. link. (2011-07-16 , ''[[Australian Geographic]]'', May 21, 2010.)
20. Smyth, Chris. (2010-05-19). "World's smallest water lily comes from Rwanda to your window sill". [[The Times]].
21. (2014-01-13). "World's smallest waterlily stolen after being dug up". [[ITV (TV network).
22. Thomas, M. B., Sibomana, P., & Dumbo, B. (2024). [https://www.researchgate.net/publication/379607846_Celebrating_an_Extinct_in_the_Wild_Waterlily_Rescue_in_Rwanda Celebrating an "Extinct in the Wild" Waterlily Rescue in Rwanda.] Water Garden Journal, 39(1).
23. Povilus, R. A., Martin, C. A., & Gehring, M. (2024). [https://www.biorxiv.org/content/biorxiv/early/2024/03/17/2024.03.15.585284.full.pdf Imprinting and DNA methylation in water lily endosperm: implications for seed evolution.] bioRxiv, 2024-03.