Do soil microbes help plants to adapt to their local environment?

MNA’s mission includes studying Michigan’s natural history. While every visit to a sanctuary brings a chance of expanding your knowledge and appreciation of nature, MNA also seeks to support dedicated scientists who try to understand our world and its fascinating flora and fauna. When done in a way that is compatible with conservation, MNA encourages scientific research on sanctuaries.

This post, which will be first in a series, was written by Tomomi Suwa, who is a graduate student in Dr. Jen Lau’s lab at Michigan State University’s Kellogg Biological Station. She is studying hog peanut, a wildflower native to Michigan that occurs on Palmer Memorial Nature Sanctuary in Southwest Kalamazoo County. To learn more about her research, visit tomomisuwa.com or Dr. Jen Lau’s website

Tomomi Suwa. Photo: Kate Webbink

Tomomi Suwa. Photo: Kate Webbink

Plants have developed many great ways to cope with harsh environmental stresses such as drought, heat and salinity. Because plants can’t move, one coping strategy is to produce a lot of seeds that can disperse far and hope that at least few of them will land on a suitable spot. A second strategy is to evolve traits that help plants deal with the stressful environment over time. This is called adaptation. Evolution of adaptive traits, however, may take a long time, as you can imagine. So the third strategy is to get “help” from other organisms. For example, if plants end up on a poor nutrient soil, they might be able to associate with fungi and bacteria that can facilitate finding nutrients.

My research focuses on how soil bacteria make it possible for plants to live in different habitats. Rhizobia, a type of soil bacteria, live inside the roots of some plants and act like natural fertilizer. Rhizobia can convert nitrogen in the atmosphere into ammonia, a form of nitrogen plants can use. In turn, plants can provide sugar to the rhizobia. This beneficial interaction is called mutualism. Rhizobia can help plants grow in areas where they might not live otherwise. Just like human relationships though, plants and rhizobia may not be compatible, or one of the partners may not even be available! For example, rhizobia may not survive or convert nitrogen effectively in certain environmental conditions, like in shade or areas that have high nitrogen in the soil.

flowering hog peanut

Flowering hog peanut. Photo: Tomomi Suwa

Using a native plant called the hog peanut (Amphicarpaea bracteata), I am looking at how the rhizobia in its roots can make it possible for plants to live in different habitats. Hog peanut is an annual legume species, closely related to soybean. What’s neat about hog peanut is that the plants can set seeds aboveground and belowground!

Hog peanut tends to grow in small patches in the forest and wetlands but it’s unclear why they grow in certain microhabitats. Is it because rhizobia are distributed in a patchy way, or is it because rhizobia benefit plants differently in various environmental conditions? I am currently doing field and greenhouse experiments to test this hypothesis. I started this project about two years ago and so far, I conducted some field observational studies in southwest Michigan, including at Kalamazoo Nature Center, Pierce Cedar Creek and MNA’s Palmer Memorial Nature Sanctuary. I don’t have answers to these questions yet, but I should be able to tell you more about it in a couple more years… so stay tuned!