An orchid that never blooms

January 11, 2018, Kobe University
An orchid that never blooms
Figure 1: L. nigricans in Iwata, Nishimuro County, Wakayama prefecture. The flowers never bloom, but the plant still fruits . Credit: Kobe University

A flower identified as Lecanorchis nigricans has been revealed to be a different identity, Lecanorchis nigricans var. patipetala. Both species are self-pollinating, but the flowers of the true L. nigricans never open.

The findings were made by Associate Professor SUETSUGU Kenji (Kobe University), FUKUNAGA Hirokazu (independent botanical researcher), SHIMAOKA Chie and Professor SAWA Shinichiro (both Kumamoto University). The research was published in the online edition of Phytokeys on January 10.

Some have evolved to be parasites, feeding off host fungi. These plants are known as mycoheterotrophs. They don't photosynthesize, so they only show themselves above ground for brief periods when fruiting or in flower. This makes them hard to find and classify, and the true identities of many species remain a mystery. Professor Suetsugu works with other researchers to document mycoheterotrophic plants in Japan.

Professor Suetsugu's research team noticed that L. nigricans (found in Japan's Miyagi prefecture and Kochi prefecture) bears fruit without blooming at all. The flower has spatula-shaped purple-tipped petals that don't branch. From these characteristics the team were able to identify it as L. nigricans or a close relative. However, the species known as L. nigricans is documented as having that fully open. This open-flower (chasmogamous) L. nigricans is found in many parts of Japan.

An orchid that never blooms
Figure 2: L. nigricans var. patipetala in Kochi city, Haruno. The flowers open fully. Credit: Kobe University

L. nigricans was first discovered in 1931 by HONDA Masatsugu in Japan's Wakayama prefecture. In the plant description, he wrote "The flowers are not open, and the petals are connected to form a cylindrical tube." From this description, it seems that the original L. nigricans did not bloom (cleistogamous). Professor Suetsugu's team went to the place where L. nigricans was first discovered and verified that the species of L. nigricans in this region never opens its flowers (fig. 1). In other words, the original L. nigricans is the variety that does not bloom. After further examination, the team found that this variety has other features that distinguish it from the open-flower L. nigricans: the closed-flower variety has smaller flowers, the colored area of the petals is larger, and the hairs at the end of the petals are branched.

So what should we call the more common open-flower variety, if it is not L. nigricans? In 1981, SAWA Yutaka presented the open-flowering variety found in Kochi prefecture as L. nigricans var. patipetala. However, his description of the plant was very brief, and it was hard to go against the general assumption that L. nigricans is an open-flowering plant.

L. nigricans var. patipetala is generally the more common variety in Japan (in Kochi prefecture the closed-flower L. nigricans is more common). This may have led to the widely-held misconception that the L. nigricans var. patipetala is L. nigricans. It is now clear that the species discovered by SAWA Yutaka is the same as the open-flower L. nigricans in other locations (see fig. 2).

As well as abandoning photosynthesis, the L. nigricans also self-pollinates – its flowers remain buds until they fall. Non-photosynthesizing plants such as L. nigricans often grow on the dark forest floor, an environment that bees and butterflies rarely visit. Because of this, L. nigricans and L. nigricans var. patipetala are both self-pollinating species. L. nigricans may have stopped opening its flowers because this used up too many resources. Similar evolutionary patterns are occurring in other mycoheterotrophic plants.

"When plants give up photosynthesis, this changes their relationship with other organisms, such as the insects who may pollinate them," comments Professor Suetsugu. "Through taxonomic and ecological research on mycoheterotrophs, I will continue to study the changes that take place when plants make the extreme decision to abandon photosynthesis."

Explore further: New non-photosynthesizing plant species discovered on Ishigaki island, Japan

More information: Kenji Suetsugu et al. The taxonomic identity of three varieties of Lecanorchis nigricans (Vanilleae, Vanilloideae, Orchidaceae) in Japan, PhytoKeys (2018). DOI: 10.3897/phytokeys.92.21657

Related Stories

Plant discovered that neither photosynthesizes nor blooms

October 14, 2016

Project Associate Professor Kenji Suetsugu (Kobe University Graduate School of Science) has discovered a new species of plant on the subtropical Japanese island of Kuroshima (located off the southern coast of Kyushu in Kagoshima ...

The origin of flower-making genes

January 11, 2018

Flowering plants have evolved from plants without flowers. It is known that the function of several genes, called MADS-box genes, creates shapes peculiar to flowers such as stamens, pistils and petals. Plants that do not ...

New plant species discovered on Yakushima

February 19, 2016

Suetsugu Kenji, a Project Associate Professor at the Kobe University Graduate School of Science, has discovered a new species of plant on the subtropical Japanese island of Yakushima (located off the southern coast of Kyushu ...

Two new species of orchids discovered in Okinawa

April 10, 2017

Two new species of parasitic plants have been discovered on the main island of Okinawa, Japan. The discovery was made by Project Associate Professor SUETSUGU Kenji (Kobe University Graduate School of Science), who named them ...

Recommended for you

Strep bacteria compete for 'ownership' of human tissue

December 10, 2018

A well-accepted principle in the animal kingdom—from wasps to deer—is that creatures already occupying a habitat nearly always prevail over competitors from the same species that arrive later. Such infighting for the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.