The Research:

Background Information for Teachers

Urban environments are clearly heavily impacted by human activities. There are a lot of species that live in cities, and the conditions they experience can be quite different than the conditions they would experience if they lived in rural environments. For example, cities tend to be noisier than rural areas, and birds that live in cities tend to be more aggressive. Animals also often have different diets in urban than rural areas (think of all the food in garbage cans). Urban-rural differences also affect plants – not only are city plants often mowed, but summer temperatures in cities are hotter than temperatures in nearby areas, and temperature is an important determinant of plant growth. Both observational and experimental approaches can be used to understand how the ecology and evolution of organisms is affected by urban environments. Peter Tiffin, a professor at the University of Minnesota, and his collaborators Mohamed (Mo) Yakub and Amanda Gorton, have been interested in characterizing how plant growth and evolution is affected by urban environments. We also thank Mo for having developed an earlier incarnation of the Symbiosis in the Schools community science activities.

Data you collect, analyze, and share with students from other schools will contribute to understanding of how plant ecology and evolution is affected by urban environments. Having a lot of classes and students collect data will allow for a broader picture of the diversity of habitats – and the plants found in those habitats – than could be achieved by just a few researchers.

Research Goals:
Determine if plant growth in urban areas differs from plant growth in rural areas
Characterize the local habitats in which those plants are found growing
Determine whether the urban and rural populations have adapted (evolved in response to natural selection) to these environments

You will be working with a plant species that is commonly found in cities: Trifolium repens (common name: White clover), as well as a bacteria (Rhizobium leguminosarum or R. leguminosarum) that forms a symbiotic relationship with this plant.

This symbiotic relationship is an interesting one. Nitrogen is the nutrient that most often limits plant growth. Most plants can obtain nitrogen only when it is available in certain, specific forms in the soil. Air is 78% nitrogen, but plants can’t use that form of nitrogen. When clover and other legume plants are growing in soils with limited available nitrogen, they form a symbiosis with rhizobia bacteria. When the bacteria are growing inside the plant, in a special root structure called a nodule, the bacteria are able to convert nitrogen in the air into a form the plant can use. In exchange, the bacteria get food from the plant and a nice place to live and reproduce. Given the importance of these bacteria for plant growth and reproduction, Peter Tiffin and colleagues are researching how this plant-bacteria pairing differs in frequency, benefits, and rhizobia between urban and rural environments.

Data you collect, analyze, and share with students from other schools will contribute to understanding of how plant ecology and evolution is affected by urban environments. Having a lot of classes and students collect data will allow for a broader picture of the diversity of habitats – and the plants found in those habitats – than could be achieved by just a few researchers.

Research Goals:
Determine if plant growth in urban areas differs from plant growth in rural areas
Characterize the local habitats in which those plants are found growing
Determine whether the urban and rural populations have adapted (evolved in response to natural selection) to these environments

You will be working with a plant species that is commonly found in cities: Trifolium repens (common name: White clover), as well as a bacteria (Rhizobium leguminosarum or R. leguminosarum) that forms a symbiotic relationship with this plant.

This symbiotic relationship is an interesting one. Nitrogen is the nutrient that most often limits plant growth. Most plants can obtain nitrogen only when it is available in certain, specific forms in the soil. Air is 78% nitrogen, but plants can’t use that form of nitrogen. When clover and other legume plants are growing in soils with limited available nitrogen, they form a symbiosis with rhizobia bacteria. When the bacteria are growing inside the plant, in a special root structure called a nodule, the bacteria are able to convert nitrogen in the air into a form the plant can use. In exchange, the bacteria get food from the plant and a nice place to live and reproduce. Given the importance of these bacteria for plant growth and reproduction, Peter Tiffin and colleagues are researching how this plant-bacteria pairing differs in frequency, benefits, and rhizobia between urban and rural environments.