As Missouri enters the fall, one last wave of wildflowers are blooming now, before the winter frosts start. Throughout the state, asters, goldenrods, and other late-bloomers paint Missouri’s varied woodlands, prairies, meadows and glades in shades of yellow, pink, purple and white. But hidden among the tall grasses and undergrowth this time of year you can sometimes find something rarer – native orchids. People often associate orchids with tropical areas, but Missouri is home to more than 30 species of orchids, and while their flowers are typically pretty showy, a lot of the crucial action with orchids happens underground.
Malissa Briggler is a Missouri Department of Conservation botanist who specializes in rare plants, and orchids typically fall into that category. "Most of our orchids are considered rare in the state," Briggler said. "Any orchid you find across the state are not going to be very common; they’re pretty scattered and you never find a whole lot in one area," she added.
The reason? Orchids, more than other plants, are very particular about the conditions they’ll grow in. If you were to try to transplant an orchid from the wild, which you shouldn’t do anyway, because they’re so rare, it probably wouldn’t survive the process because of one crucial factor.
"The orchids do require a mycorrhizal fungal association. That means that there’s fungus growing in the ground, that is required for that orchid to survive," Briggler explained. The fungus grows on the roots of plants, and forms specific, often symbiotic relationships with plants. With orchids, it’s fair to say that relationship is complicated. Briggler said, "It is a very lesser-known field of study."
I made my way to Tucker Greenhouse at the University of Missouri to find someone who works in that field. Sarah Unruh is a doctoral student who studies the orchid-mycorrhiza dynamic. Unruh said orchids need help from the outset. "If you think of a corn kernel, corn has all that starchy goodness that we like to eat but it’s actually food for the seed to give it energy so it can pop up above the surface," Unruh explained. "Orchids don’t have that little seed leaf."
Instead, orchids rely on the fungus – with specific species of fungi having corresponding orchid species. The fungi produce sugars and other foods orchids need in those developmental stages. In most other plant-fungus relationships, plants are the ones that provide food to the fungi through photosynthesis, and the fungi in turn provide water or certain minerals.
At first, the orchid's relationship with mycorrhiza puzzled researchers. "It seemed like maybe the orchid was a parasite or a predator of some kind, because it wasn’t obvious what the fungus was getting out of it at first, but it looks like maybe some kind of nitrogen compound," Unruh said. Her work aims to better understand that exchange, and to do that, she uses genome sequencing.
"Basically, I grow a lot of fungi, I grind them up in liquid nitrogen, and then put chemicals back and forth to get the DNA out of the nucleus." Genes can serve as clues to understand the relationship between mycorrhiza and plants – if the fungi are missing certain genes, they might need to rely on plants to carry out corresponding functions. "And then we can see what it has, what it doesn’t, how it’s related to other fungi," Unruh said.
So far, Unruh has two genomes, but still has more data to generate before she can begin analyzing it. Her work could shed light not only on the nature of the orchid-mycorrhiza relationship, but how that relationship came to be in the first place.
If you want to see some orchids yourself, without a microscope, your best bet this time of year is the Spiranthes genus. Known commonly as ladies tresses orchids, these diminutive plants are distinguished by their spiraling white flowers, which grow up along a leafless green stem. They’re sometimes found on lawns or in old fields, but in the wild grow on prairies and glades.
