Update (October 8, 2021): A September 19 paper in New Phytologist challenges the idea that cantils are a distinct organ, instead suggesting that the structures are a quirk of aneuploidy.

To any devoted reader of The Scientist, it should come as no surprise that even the most intensely studied organisms have organs, tissues, and cell types unknown to science. Just last week, neuroscientists described a pair of novel brain cell types in mice. And in recent years, scientists identified for the first time a lymphatic system in the brain that’s present in both mice and humans.

See “New Discoveries in Human Anatomy

The newly described cantil is the horizontal arm projecting from the left side of the stem of this Arabidopsis thaliana specimen.
T. Gookin

Yesterday (June 15), plant biologists reported in Development that the much-studied model plant Arabidopsis thaliana possesses an organ that had been overlooked by researchers and naturalists for centuries. The cantil—named for its cantilever-like form—reaches out horizontally from the stem and supports the pedicel, a stalk that grows vertically and is topped off by a flower.

“I think this is going to be one of those papers where people will look at it and go, Oh, I saw that once! I didn’t know what it meant!” Dominique Bergmann, a plant biologist at Stanford University who wasn’t involved with the study, tells National Geographic.

Those Arabidopsis researchers who hadn’t noticed it before have a good excuse. The authors demonstrate that cantils only form under certain conditions—in particular, when daylight hours are kept short. Typically, as plants experience longer days while spring transitions to summer, they go from shoring up resources to producing flowers. Cantils arise when springlike conditions, and therefore flowering, are delayed. But labs studying Arabidopsis usually maintain longer days to stimulate flowering, according to Science News, and some fast-growing varieties have lost the ability to grow cantils, making them rarities in the lab.

Timothy Gookin, who led the work as a postdoc at Penn State, first spotted the structures when he was experimenting with plants whose leaves wilt under short-day conditions. He didn’t think much of it—after all, these were mutant Arabidopsis—until he saw them again on plants harvested from the wild, National Geographic reports.

His subsequent investigations pegged several genes involved in cantil formation, although the function of cantils remains unknown.

“If you told me of a new organ in a weird plant in Amazonia, I wouldn’t be surprised at all,” François Parcy, a plant biologist at CNRS in Paris who was not involved in the study, tells Science News. “What struck me is this happened in Arabidopsis. This is something that’s really surprising.”