Researchers report finding the first bidirectional color-changing flower variety

An enlarged view that clearly shows the alternating orange and pink colors of the flower petals. Credit: ©2022 H. Tsukaya CC-BY

We all love flowers, and one of the most appealing things about flowers is probably the wide variety of shapes, sizes, and of course the colors they come in. But did you know that some flowers can change color? While not all flowers, this trait has been observed in hundreds of different species for at least a few decades.

It is thought that the color-changing flowers do this because they signal to pollinating insects that the flower is ready to provide the nectar or pollen that rewards them. This is considered an “honest” signal.

However, the reverse can also be seen; some plants show a “dishonest” signal, some of their flowers show their default color while others show their signal color. This behavior is thought to increase the overall visibility of the plant from a distance to possible pollinators.

Whatever the strategy of the plant in question, all specimens of color-changing flowers found were one-sided: once the color is changed, it does not return. So imagine the surprise that University of Tokyo Professor Hirokazu Tsukaya must have felt when he saw a flower of the Causonis japonica plant change color and then change again and again.

“Although I studied this plant in detail after discovering it had at least two cultivars in 2000, the bidirectional color-changing flowers were a completely unexpected find,” Tsukaya said.

“My colleague Professor Nobumitsu Kawakubo from Gifu University is an expert in time-lapse, long-term video recordings of pollinating flowers. He and his student initially sought to explore pollination behaviors between different species of Causonis japonica, and hoped to see what they recognized changed from its default orange color to bright pink. But when they viewed the time-lapse video, and they couldn’t believe it when they saw this change go back and forth between the two states. They gave me the information. This finding forced us to find out why, and we started a collaboration.”

The unique bidirectional color-changing petals could only be observed now because in nature the plant was a chaotic bunch of buds, leaves and flowers growing quite fast. Therefore, it was not really possible to track individual flowers over time. But thanks to carefully controlled time-lapse video recording, individual flowers can now be viewed, thus leading to observations like this one. Credit: ©2022 H. Tsukaya CC-BY

Through careful time-lapse videos from the field and detailed observations in the lab, Tsukaya was able to find out what physiological changes occur simultaneously with the color changes of the flowers.

“The initial orange state coincides with the male stage of the flower’s maturation, in which it secretes nectar,” Tsukaya said.

“The flowers turn pink when the stamen – the male part – ages and breaks off. After just a few hours the pistil – the female part – begins to mature, secretes nectar and the flower turns orange again. When this stage is over, the flower turns pink. The main chemical responsible for the color change is the orange-yellow carotenoid; its “The accumulation and decay cycle is also the fastest known to date. This fact was another surprise for us.”

The chemical name carotenoid sounds a bit like the word “carrot.” This is no coincidence as it is the same chemical that gives typical carrots their orange hue. It’s a good source of vitamin A, and given that the color-changing flowers show the fastest accumulation of carotenoids ever seen, it’s not surprising that the researchers think their discovery may have some application in the future in developing faster-ripening or higher-containing carotenoid-containing vegetables. yield of useful vitamins.

“Our next step will be to find out what drives the behaviors we observe,” Tsukaya said.

“The big question we have is: At what level are the phases of the cycles regulated? Is it due to proteins caught in the feedback loop or is something going on at the genetic level? We will continue to explore this and hope to find a solution. Due to the vigorous nature of the agriculturalists in Japan a few hundred years ago, Causonis japonica It’s strange to think that you hate . But a novelist named Kyoka Izumi has written about them so positively that I wonder if it helps keep the interest in protecting them. Whatever the reason, I’m glad they’re here to share their secrets with us. I wonder what we’ll discover next.”

The research appears in the journal Scientific Reports.

More information:
Released flower color changes of Causonis japonica (Thunb.) Raf. (Vitaceae) due to sexual phase changes, Scientific Reports (2022). DOI: 10.1038/s41598-022-24252-z

Provided by the University of Tokyo

Quotation: Researchers reported on December 1, 2022 that they had found the first bidirectional color-changing flower variety (2022, December 1), retrieved from

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