Navigation Links
Pesticides choke pathway for nature to produce nitrogen for crops


Jennifer E. Fox, NIH/NRSA postdoctoral fellow at the University of Oregon, has shown that many pesticides interfere with the ability of legumes to recruit soil bacteria needed to provide a natural fertilizer to crops. Credit: University of Oregon
Many farmers applying pesticides to boost crop yields may instead be contributing to growth problems, scientists report in a new study.

According to years of research both in the test tube and, now, with real plants, a team of scientists reports that artificial chemicals in pesticides – through application or exposure to crops through runoff – disrupt natural nitrogen-fixing communications between crops and soil bacteria. The disruption results in lower yields or significantly delayed growth.

In a paper appearing online this week ahead of the regular publication by the Proceedings of the National Academy of Sciences (PNAS), the five-member team reports that agrichemicals bind to and block connections to specific receptors (NodD) inside rhizobia bacteria living in root nodules in the soil. Rotation legume crops such as alfalfa and soybeans require such interaction to naturally replace nitrogen levels that, in turn, benefit primary market crops like corn grown after legume rotations. __IMAGE_2

Legume plants secrete chemical signals that recruit the friendly bacteria, which work with the plants to convert atmospheric nitrogen into ammonia that, then, is used as fertilizer by the plants.

"Agrichemicals are blocking the host plant's phytochemical recruitment signal," said the study's lead author, Jennifer E. Fox, a postdoctoral researcher in the Center for Ecology and Evolutionary Biology at the University of Oregon. "In essence, the agrichemicals are cutting the lines of communication between the host plant and symbiotic bacteria. This is the mechanism by which these chemicals reduce symbiosis and nitrogen fixation."

Fox began the project as a doctoral student with John A. McLachlan, director of the Center for Bioenvironmental Research at Tulane University. She is working at the University of Oregon as a National Institutes of Health and National Research Service Award postdoctoral fellow under Joe Thornton, a professor of biology who focuses on phylogenomics and nuclear receptor genes.

Fox and colleagues began detailing their findings in the journal Nature (2001) and Environmental Health Perspectives (2004), testing more than 50 chemicals, including pentachlorophenol (PCP), in in-vitro assays. The paper in PNAS reports their in-vivo findings using real plants and bacteria.

None of the chemicals used in the research, including PCP, proved to be toxic to either the plants or bacteria, Fox said, "but PCP was unique in that it inhibited both seed germination and nitrogen fixation." More than 20 commonly used agricultural chemicals shared the same mechanism of action as PCP, but with varying amounts of signal disruption.

Fox, McLachlan and colleagues, in their PNAS paper, pointed to two published studies from 2000 that had found significant declines in both crop yield per unit of synthetic nitrogen fertilizer added and also a significant decline in overall symbiotic nitrogen fixation.

The most common explanation for the observations is an overuse of agrichemicals applied to legume crops. That practice sets up "a vicious cycle," Fox said, because it reduces a legume crop's natural need for nitrogen fixation but leaves a shortage of natural nitrogen in the soil for the next year's crop to utilize. Thus, she said, there is the need for yet more fertilizer.

Other reasons, Fox said, have been poor soil quality due to overuse, which strips nutrients such as nitrogen and phosphorous from the soil, and to tillage, which interrupts root structures and disturbs the nitrogen-fixing bacteria when soil is turned.

"Our research provide s another explanation for declining crop yields," Fox said. "We showed that by applying pesticides that interfere with symbiotic signaling, the overall amount of symbiotic nitrogen fixation is reduced. If this natural fertilizer source is not replaced by increased application of synthetic nitrogen fertilizer, then crop yields are reduced and/or more growing time is needed for these crops to reach the yields obtained by untreated crops. We feel that this is a previously unforeseen factor contributing to declining crop yields."

The researchers say that field-wide experiments now are needed, in addition to tests to determine the exact elements of pesticides that inhibit natural plant-bacteria interaction.


'"/>

Source:University of Oregon


Related biology news :

1. Pesticides in the nations streams and ground water
2. Pesticides need sunscreen to beat the heat
3. Scientists find missing enzyme for tuberculosis iron scavenging pathway
4. Scientists identify genetic pathways essential to RNA interference
5. Opposing fat metabolism pathways triggered by a single gene
6. Viral protein influences key cell-signaling pathway
7. Newly discovered pathway might help in design of cancer drugs
8. Scientists identify genetic pathways essential to RNA interference
9. Genpathway and Baylor College of Medicine Identify New Genes in Breast Cancer
10. Scientists discover genetic pathway responsible for breast cancer cell growth
11. Bacteria that cause tooth decay able to survive without important biochemical pathway

Post Your Comments:
*Name:
*Comment:
*Email:


(Date:4/19/2017)... ALBANY, New York , April 19, 2017 /PRNewswire/ ... highly competitive, as its vendor landscape is marked by ... in the market is however held by five major ... and Safran. Together these companies accounted for nearly 61% ... majority of the leading companies in the global military ...
(Date:4/13/2017)... 2017 According to a new market research report ... Identity Administration, and Authorization), Service, Authentication Type, Deployment Mode, Vertical, and Region ... expected to grow from USD 14.30 Billion in 2017 to USD 31.75 ... ... MarketsandMarkets Logo ...
(Date:4/11/2017)... , April 11, 2017 NXT-ID, Inc. ... technology company, announces the appointment of independent Directors Mr. ... to its Board of Directors, furthering the company,s corporate governance ... Gino ... we look forward to their guidance and benefiting from their ...
Breaking Biology News(10 mins):
(Date:10/11/2017)... ... October 11, 2017 , ... ... Andi Purple announced Dr. Suneel I. Sheikh, the co-founder, CEO and chief research ... Inc. has been selected for membership in ARCS Alumni Hall of Fame ...
(Date:10/11/2017)... ... October 11, 2017 , ... Proscia Inc ... hosting a Webinar titled, “Pathology is going digital. Is your lab ready?” with ... adoption best practices and how Proscia improves lab economics and realizes an increase ...
(Date:10/11/2017)... ... October 11, 2017 , ... ... implantation and pregnancy rates in frozen and fresh in vitro fertilization (IVF) ... and maternal age to IVF success. , After comparing the results from the ...
(Date:10/10/2017)... Philadelphia, PA (PRWEB) , ... October 10, 2017 ... ... University City Science Center’s FirstHand program has won a US2020 STEM Mentoring Award. ... accept the award for Excellence in Volunteer Experience from US2020. , US2020’s mission ...
Breaking Biology Technology: