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Nymphaea thermarum

life science Maturity 5-7 Next article →

Nymphaea thermarum is a tiny species of water lily. It is endemic to Rwanda, meaning it grows nowhere else on Earth. This plant is highly significant to the scientific community. Because of its small size and rapid lifecycle, researchers use it as a model species. It is specifically used to study basal angiosperms, which are ancient flowering plants. Scientists also study its small genome, which is the complete set of genetic instructions for the plant. This genome size is 498.78 Mb. By studying this lily, researchers can better understand how seeds evolved over time.

The plant has a very specific way of blooming. It is a tropical day bloomer that follows a protogynous flowering pattern. This means the flower changes its reproductive function over two days. On the first day, the flower opens early in the morning to act as a female. It closes again in the early afternoon. On the second day, the flower opens to act as a male. This cycle helps manage how the plant reproduces. After blooming, the flower stalk bends downward. This movement ensures the fruit makes direct contact with the mud.

The physical structure of Nymphaea thermarum is quite delicate. It is a diminutive, aquatic, rhizomatous herb. A rhizome is an underground stem that grows horizontally. These rhizomes are only 1 to 5 cm long. The leaves are orbicular, which means they are circular in shape. Each leaf has a diameter between 2.8 and 3.2 cm. The leaves are peltate, meaning the stem attaches to the center of the leaf. The petals are white and measure about 1.5 to 1.6 cm long. The flower also contains four green, lanceolate sepals. These sepals are 1.7 to 1.8 cm long and have a round apex.

The reproductive parts of the flower are complex. The androecium, or the male part, consists of up to 16 stamens. These stamens decrease in size from the outer edges to the inner parts. The outer stamens are 9 to 10 mm long, while the inner ones are 5 to 6 mm long. The gynoecium, or the female part, contains 7 to 9 carpels. These carpels are fused at the base and are 4 to 5 mm long. The fruit itself is quite small, measuring 1.2 to 1.5 cm wide. Inside this fruit, you can find 300 to 400 bright red or brown, arillate seeds.

The history of this plant is a story of near loss and discovery. The German botanist Eberhard Fischer first collected a type specimen on April 25, 1987. He found them in hot springs south of Nyakabuye, Rwanda. He published the description of the species in 1988. By 2008, the plant was thought to be extinct in the wild. Local farmers in Mashyuza had diverted the freshwater hot springs for agriculture. This caused the tiny habitat, which was only a few square meters, to dry up. Fischer had previously sent specimens to the Bonn Botanic Gardens in Germany to protect them.

In 2009, a major breakthrough occurred at the Royal Botanic Gardens, Kew. A scientist named Carlos Magdalena solved the problem of growing the plants from seed. He placed seeds and seedlings into pots of loam. He kept the water level surrounding the pots consistent. Within weeks, eight plants began to flourish and mature. By November 2009, the water lilies flowered for the first time in cultivation. This success proved the species could be saved. Even more surprising, a previously unknown wild population was discovered in 2023.

Today, Nymphaea thermarum remains a subject of intense scientific interest. It has a diploid chromosome count of 2n = 28. Interestingly, its chloroplast genomes are identical to those of Nymphaea heudelotii. These genetic details help scientists map the relationships between different water lily species. While the plant is fragile in the wild, it is easy to grow in controlled settings. Some experts suggest it could even be used as a houseplant. It continues to serve as a vital link to understanding the evolution of flowering plants.

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