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Orchids have developed fringed petals to support pollinators •

The wild orchid Habenaria struck outThe beautiful white petals of the flower resemble a white egret in flight – hence the colloquial name of the flower “white egret orchid”. Although this orchid has been loved by people since ancient times, the adaptive significance of the serrated shape of the flower has remained a mystery until recently.

For three years, a team of researchers led by Kobe University in Japan conducted field experiments in which the feather-like fringe was removed, and how this change influenced the orchid’s pollinators. has been examined. Experts have found that in their natural habitat, crested orchids without this fringe tend to produce fewer healthy seeds than intact plants. The question that remained was why.

Initially, scientists thought that the petals of orchids functioned primarily as visual attractants. In the case of H. struck offhawkmoths – the primary pollinators of this species – have been observed hovering in the air while drinking flower nectar, leading researchers to speculate that they are visually attracted to the fringe of the plant.

Since the flowers of other plants pollinated by hawkmoths (such as snake gourd) also have deeply divided fringed petals, these petals were thought to have adapted to effectively attract hawkmoths, probably because fringed flowers can retain more resources than those without fringes of the same diameter.

However, if the fringe functions primarily as a visual attractant, it can be predicted that specimens without fringes would have a reduced rate of fruit production (since fruit production is an indicator of the frequency of pollinator visits).

Scientists were surprised to find that, contrary to this prediction, there was no decline in fruit production in specimens without fringes, suggesting that fringe does not in fact play a significant role in the attraction of the sphinxes. However, flowers with the fringe removed had a lower rate of healthy seeds in their fruits.

By making detailed observations of the behavior of the sphinxes, the scientists noticed that this major pollinator did not hover continuously while drinking nectar, but sometimes clutched the fringe of the petals with its middle legs. This suggests that without the stability provided by the fringe, the hornworms cannot transmit as much pollen to the plant, causing plants without fringes to receive fewer pollen grains per visit and produce fewer healthy seeds.

“The White Egret Orchid got its name because its brilliant white petals resemble the bird in flight. According to legend, the soul of a deceased White Egret Orchid is reborn as the much-loved Egret Orchid,” said the study’s lead author, Kenji Suetsugu, an associate professor of botany at Kobe University.

“Nevertheless, it is now clear that the fringes primarily stabilize the posture of the hawkmoth (the primary pollinator), increasing pollen transfer. I’m glad we’ve revealed the unexpected adaptive significance that lies at the heart of its distinctive fringe,” said he concluded.

The study is published in the journal Ecology.

By Andrei Ionescu, Personal editor