The Giant Orchid That Has No Leaves And Subsists On Fungi May Eat Itself Out Of Existence

An extremely rare giant orchid species that creeps up the trunks of very tall trees like a vine could literally be eating itself out of existence.

Erythrorchis altissima is already designated on the Environment Ministry’s red list as “critically endangered,” meaning it is at grave risk of extinction.

The flower has a bizarre biology and is only found in Kagoshima and Okinawa prefectures. It thrives on nutrients from various fungi that grow on trees, which in turn rot the host plant.

This “diet” means the orchid can survive for only limited periods until the fungi finish decomposing the trees, said Yuki Tsujita, an associate professor of applied biological sciences at Saga University here, noting that a new generation can only take over if a large number of other tall trees are available nearby.

“Areas like that are becoming rarer, as primeval forests are dwindling,” Tsujita said. “Plants of this type will perish when these forests vanish.”

Bizarrely, the orchid lacks leaves that would allow photosynthesis to take place. Yet, it typically can grow to up to 10 meters in height.

While there are a number of plants that do not photosynthesize and obtain nutrients instead from fungi that live in symbiosis in their roots, most only grow to several centimeters or just a few dozen centimeters.

It remained a mystery how Erythrorchis altissima, which is believed to be the world’s biggest plant in that group, manages to maintain its bulk.

Tsujita and her colleagues identified 37 fungal species in the roots of Erythrorchis altissima. Most of them were wood-decaying fungi, such as members of the Polyporaceae family, which decompose the trees that the giant orchid climbs.

Other plants of the group live in symbiosis only with limited types of wood-decaying fungi. No plant of that category was previously known to partner with such a wide range of wood-decaying fungi as Erythrorchis altissima does, Tsujita said.

The giant climbing orchid apparently needs a huge mass of fungi to maintain its colossal body.

It remains unknown how the giant orchid manages to live in symbiosis with so many fungi that feed on trees.

“Erythrorchis altissima could be compared to a trainer of wild animals, who knows how to handle not just tigers but also lions and bears,” said Tsujita, alluding to the risk of a mauling.

Tsujita is intrigued by the idea that the orchid species relies on meager circumstances, nutrients from a broad variety of wood-decaying fungi, to flourish.

But she noted that since the plant grows to great heights, it has the ability to scatter its seeds over a considerable area. Even so, it needs a huge pool of fungi to survive.