Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Long-term nitrogen fertilizer use disrupts plant-microbe mutualisms

24.02.2015

When exposed to nitrogen fertilizer over a period of years, nitrogen-fixing bacteria called rhizobia evolve to become less beneficial to legumes - the plants they normally serve, researchers report in a new study.

These findings, reported in the journal Evolution, may be of little interest to farmers, who generally grow only one type of plant and can always add more fertilizer to boost plant growth. But in natural areas adjacent to farmland, where fertilizer runoff occurs, or in areas where nitrogen oxides from the burning of fossil fuels settle, a change in the quality of soil rhizobia could have "far-reaching ecological and environmental consequences," the researchers wrote.


Soil microbes known as rhizobia supply much-needed nitrogen to legumes such as clover (Trifolium species). In return, legumes shelter the rhizobia in nodules on their roots and provide them with carbon.

Credit: Julie McMahon

"The nitrogen that we apply to agricultural fields doesn't stay on those fields, and atmospheric nitrogen deposition doesn't stay by the power plant that generates it," said University of Illinois plant biology professor Katy Heath , who led the study with Jennifer Lau , of Michigan State University. "So this work is not just about a fertilized soybean field. Worldwide, the nitrogen cycle is off. We've changed it fundamentally."

Not that long ago, before the advent of industrial fertilizers and the widespread use of fossil fuels, soil nitrogen was a scarce commodity. Some plants, the legumes, found a way to procure the precious nitrogen they needed - from rhizobia.

"The rhizobia fix nitrogen - from atmospheric nitrogen that we're breathing in and out all the time - to plant-available forms," Heath said. "Plants can't just take it up from the atmosphere; they have to get it in the form of nitrate or ammonium."

In return, legumes shelter the rhizobia in their roots and supply them with carbon. This partnership benefits the bacteria and gives legumes an advantage in nitrogen-poor soils. Previous studies have shown that nitrogen fertilizers can affect the diversity of species that grow in natural areas, Heath said. In areas polluted with fertilizer runoff, for example, legumes decline while other plants become more common.

In the new analysis, Heath and her colleagues looked at six long-term ecological research fields at Michigan State University's Kellogg Biological Station. Two experimental plots were located in each of six different fields. One plot in each field had been fertilized with nitrogen for more than two decades; the other, a control plot, had never been fertilized.

The researchers isolated rhizobia from the nodules of legumes in fertilized and unfertilized plots. In a greenhouse experiment, they tested how these bacteria influenced legume growth and health. The researchers found that the plants grown with the nitrogen-exposed rhizobia produced 17 to 30 percent less biomass and significantly less chlorophyll than plants grown with rhizobia from the unfertilized plots.

A genetic analysis of the microbes revealed that the composition of the bacterial populations was similar between fertilized and unfertilized plots: The same families of rhizobia were present in each. But rhizobia from the fertilized plots had evolved in a way that made them less useful to the legumes, Heath said.

"This study tells us something about mutualisms and how they evolved," she said. "Mutualisms depend on this balance of trade between the partners, this special nitrogen-carbon economy in the soil, for example. And when the economy changes - say when nitrogen is no longer scarce - these mutualisms might go away."

The research team also included Dylan Weese, of Michigan State University and St. Ambrose University; Bryn Dentinger, of the Royal Botanic Gardens, in Surrey, UK; and Jennifer Lau, of Michigan State University.

The National Science Foundation supported this research.

Editor's notes:

To reach Katy Heath, call 217-265-5473; email kheath@illinois.edu.

The paper, "Long-term nitrogen addition causes the evolution of less cooperative mutualists," is available online or from the U. of I. News Bureau.

Media Contact

Diana Yates
diya@illinois.edu
217-333-5802

 @NewsAtIllinois

http://www.illinois.edu 

Diana Yates | University of Illinois

More articles from Agricultural and Forestry Science:

nachricht Energy crop production on conservation lands may not boost greenhouse gases
13.03.2017 | Penn State

nachricht How nature creates forest diversity
07.03.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>