“`html
A researcher at Kobe University has revealed the function of a plant structure that inspired the name of a fungus-eating plant, 130 years after it was first named, uncovering a new way that plants achieve reproduction.
Makino Tomitaro, a prominent figure in Japanese botany, named around 1,000 species and identified about 600 new plants from 1887 to 1957. Among his significant finds was the small orchid Stigmatodactylus sikokianus, which he discovered in 1889. This plant earned its name due to its unique, tiny, finger-like extension on the stigma, the female part of the flower that receives pollen. Although it is well-regarded as one of Japan’s distinct orchids, the function of this structure remained unclear until now.
Suetsugu Kenji, a botanist at Kobe University with a focus on orchids that derive nutrients from soil fungi instead of sunlight, has studied Stigmatodactylus. He describes his research interests: “I’m particularly fascinated by their pollination mechanisms, using an approach that merges taxonomy, ecology, and evolutionary biology.” His curiosity led him to explore the purpose of the finger-like structure that gave the genus its name and its role in the environment. To investigate these questions, Suetsugu systematically observed insect visitation patterns and the conditions necessary for seed production in these plants. He also studied the flower’s structure at different growth stages to learn how pollination and fertilization take place.
His research, published in Plants, People, Planet, shows that these plants mostly rely on self-pollination, meaning they do not depend on insects for pollen transfer, and this process occurs roughly three days after the flowers bloom. This timing in self-pollination holds notable ecological implications. Since these plants grow in the dim environments of forests, often among decaying leaves and without nectar to attract pollinators, they rarely receive visits from potential pollinators. Suetsugu states: “Even though self-pollination helps ensure reproductive success, depending solely on this method raises the risk of inbreeding. This scenario may encourage the development of strategies that balance self-pollination with outcrossing. Delayed self-pollination, which happens after all chances for outcrossing have been explored, seems to be one such adaptive strategy—a backup mechanism.”
Further insights from microscopy revealed functions of the finger-like extension in self-pollination. By the third day after blooming, the stigma collapses, and the finger-like appendage meets the pollen-laden anther, allowing pollen tubes to grow through the appendage into the stigma and then into the ovary, facilitating fertilization. Suetsugu notes: “The movement of the stigma appendage is, to our knowledge, a unique self-pollination mechanism in orchids.” He adds: “The most thrilling part of this study was uncovering this previously unrecognized mechanism, showcasing the complex evolutionary routes plants can evolve to secure their survival.” Given that Stigmatodactylus comprises 28 species, many possessing this structure, this mechanism could also be found in other species.
The botanist from Kobe University concludes: “The importance of this discovery lies in its ability to link historical botanical studies with modern scientific research. It emphasizes the necessity of combining thorough taxonomic work with ecological and evolutionary studies to gain fresh insights. In a period when research tends to be more specialized, taxonomy and ecology are often explored separately. This study shows that traditional natural history research, which brings together taxonomy, evolution, and ecology, continues to hold the potential to reveal new phenomena today.”
This research was supported by the Japan Science and Technology Agency (grant JPMJPR21D6).
“`
