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:4/19/2016)... 2016 The new GEZE SecuLogic ... web-based "all-in-one" system solution for all door components. It ... the door interface with integration authorization management system, and ... The minimal dimensions of the access control and the ... installations offer considerable freedom of design with regard to ...
(Date:4/13/2016)... -- IMPOWER physicians supporting Medicaid patients in Central ... in telehealth thanks to a new partnership with higi. ... patients can routinely track key health measurements, such as ... when they opt in, share them with IMPOWER clinicians ... retail location at no cost. By leveraging this data, ...
(Date:3/23/2016)... WAKEFIELD, Massachusetts , March 23, 2016 ... kombiniert im Interesse erhöhter Sicherheit Gesichts- und ... Xura, Inc. (NASDAQ: MESG ... heute bekannt, dass das Unternehmen mit SpeechPro ... insbesondere aus der Finanzdienstleistungsbranche, wird die Möglichkeit ...
Breaking Biology News(10 mins):
(Date:5/23/2016)... (PRWEB) , ... May 23, 2016 , ... The need for blood donations in South ... week by the South Texas Blood & Tissue Center, blood donations are on the decline. ... years, and they are down 21 percent in South Texas in the last four years ...
(Date:5/23/2016)... England , May 23, 2016 ... May 25 th at 10:15 a.m. ET before the ... the role genetically engineered mosquitos can play in controlling the ... carrier of the Zika virus.      (Logo: ... engineered male mosquito with a self-limiting gene. Trials in ...
(Date:5/23/2016)... Alto, CA (PRWEB) , ... May 23, 2016 ... ... and public interest organization focused on molecular nanotechnology, announced the winners for the ... of pioneer physicist Richard Feynman, are given in two categories, one for experiment ...
(Date:5/20/2016)... ... May 20, 2016 , ... Kablooe Design, a leading provider of product ... official 25th anniversary of the business. “We have worked hard to build long-term relationships,” ... for the privilege and honor of serving their product design and development needs through ...
Breaking Biology Technology: