Pinanga subterranea: The Palm That Flowered Underground

by | Botany

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This morning, a news story broke that a rare palm was found to flower and fruit underground. This is an incredible story of a modern scientific discovery in several ways:

The New Discovery 

This story comes with two new discoveries. First, a species of palm that is newly described to science. Secondly, a flowering and fruiting phenomenon that has never been observed in palms before.
 
Let’s talk first about the new species of palm. Typically, because of the short growth pattern of these plants, they are often mistaken as seedlings of other species. Palms in this region are exceptionally difficult to identify in surveys and the identification of this new species was the result of researchers’ efforts to compare these plants with all other known species of Pinanga palm. (1)
 
This palm is called Pinanga subterranea, a native palm to the tropical islands of Borneo. It is well-known to the locals as they enjoy its bright red, juicy fruits as a forest snack, and it is commonly sought after by hungry bearded pigs.The team who discovered the plants are researchers with the Royal Botanic Gardens at Kew who partnered with indigenous communities in Borneo to learn about the native flora. In their paper, they noted four different local common names:

“It is known in at least three Bornean languages by four different names: Pinang Tanah (Malay, West Kalimantan), Pinang Pipit, Muring Pelandok (both Kadorih, Central Kalimantan), and Tudong Pelandok (Iban, Sarawak) (Randi et al., 2023).”

Why Does It Fruit Underground?

In short, we have no idea yet. While rare, there are plants that develop their fruits underground, though the primarily flower above-ground first. The most famous example is that of the common peanut. This phenomenon is called geocarpy.
 
Geoflory, on the other hand, is when a plant flowers underground, which is exceedingly rare. The authors of the paper note that these phenomena are only known to occur in an underground orchid in the Rhizanthella genus. Similarly, the author notes that an underground pitcher plant (Nepenthes pudica) was recently newly-described in Borneo, which is another first description for science.
 
Additionally, the phenomenon of developing fruits underground usually only occurs in arid or desert environments where it’s important that the seed is protected from dangerous heat and desiccation. There are many questions that remain about how this palm’s full geocarpy (underground fruiting) and geoflory (underground flowering) affects its ability to find pollinators, or why it evolved in that fashion.
 
The authors pose many questions in the discovery, such as what pollinates the plant’s underground flowers, and what disperses the seeds to prevent competition with the mother plant?
 
Currently, it is suspected that bearded pigs play a role in the dispersal of seeds, as they’ve been observed digging up and retrieving the fruits. Seeds that were later retrieved from the bearded pigs’ droppings were cultivated successfully. Additionally, the authors write, beetles have been observed pollinating other Pinanga species palms, which may point to them as a potential vector.
Pinanga subterranea. (a) Mature, fruiting individual, with leaf litter and soil partially removed around base to expose tip of infructescence; (b) base of plant, with top layer of soil removed to expose ripe red fruits (left) and unripe green-brown fruits (right); (c) ripe fruits. Scale bar = 1 cm; (d) partially excavated infructescence bearing young fruits; (e) bearded pig (Sus barbatus), a seed disperser of Pinanga subterranea. Localities: (a–c) Gunung Niut Natural Reserve, West Kalimantan, Indonesia, (d) Lanjak Entimau Wildlife Sanctuary, Sarawak, Malaysia, (e) Bako National Park, Sarawak, Malaysia. Photographs: (a–c) Agusti Randi, (d) William J. Baker, (e) Benedikt G. Kuhnhäuser. Image and Caption Source: https://doi.org/10.1002/ppp3.10393

Image credit: https://nph.onlinelibrary.wiley.com/doi/full/10.1002/ppp3.10393

Why Is This a Big Deal for Palms?

Palms are considered angiosperms, or flowering plants, so you could expect them to flower and produce seeds (whereas a gymnosperm, naked seed, such as a cycad would only produce cones.) What scientists have never seen before, however, is a palm that flowers and fruits entirely underground. This is a novel discovery not just for plants, but especially for palms. 
 
“Both discoveries highlight Borneo as a hotspot for biodiversity, which may hold many more as yet undescribed species that may change the way we think about the biological world surrounding us.”
Benedikt G. Kuhnhäuser

Most palms are under threat of extinction because of land development and changing climate patterns. This is particularly true in Borneo, which is known as a hotspot for biodiversity on Earth. Still, this is a wonderful discovery of ecosystem relationships in action that makes an inspiring story. Perhaps not every corner of the world has been mapped yet, and there’s still plenty of discoveries for all of us to make with enough dedication and motivation.

As a final note, the authors of the paper which was published yesterday, are listed as Benedikt G. Kuhnhäuser, Agusti Randi, Peter Petoe, Paul P. K. Chai, Sidonie Bellot, and William J. Baker. This is an open-access paper available for anyone to read, and it is presented in an excellent format for a wider range of audiences, not just for the scientific. See the references list to get the link to the paper. (2)

References
References
https://phys.org/news/2023-06-hidden-plain-sight-rare-palm.html
Kuhnhäuser, B. G., Randi, A., Petoe, P., Chai, P. P. K., Bellot, S., & Baker, W. J. (2023). Hiding in plain sight: The underground palm Pinanga subterraneaPlants, People, Planet, 1– 6. https://doi.org/10.1002/ppp3.10393

 

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About Destynnie K. Berard
I am a lifelong naturalist who believes a good sense of humor is essential to staying happy. ★ After traveling for years, I settled in New England, falling in love with the diverse landscape the Northeast has to offer, and began pursuing conservation in earnest. ★ My career background is in enterprise marketing and communications, which provides me with a unique perspective of ecological relationships.

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