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Glenbard East High School ESRP 2014

The Effects of Glyphosate on Growth, Metal Concentration and Distribution in Transgenic Soybean

Authors:

  • Students:
    • Thomas Faragoi
    • Wendy Guraziu
    • Jessica Jancaric
    • Bart Pecyna
  • Teachers:
    • Karen Beardsley
  • Mentors:
    • Antonio Lanzirotti (University of Chicago, Center for Advanced Radiation Sources)
    • Matthew G. Newville (University of Chicago, Center for Advanced Radiation Sources)

Advanced Photon Source Sector 13: GSECARS

Roundup Ready┬« transgenic soybeans have bacterial genes incorporated into their genome that provide an alternative biochemical pathway for the production of essential amino acids allowing the transgenic soybean to resist the effects of glyphosate(Roundup┬«).  In the nontransgenic plant this biochemical pathway is blocked by glyphosate, ultimately resulting in the death of the plant.  The complete effects of the genetic modification are unknown, particularly with respect to effects on metal homeostasis. This experiment measured plant growth and metal concentration and distribution in glyphosate-treated transgenic soybean (Glycine max) and nontransgenic or conventionally bred soybean (cv. Dwight) as a way to investigate some effects of this genetic modification.  Nontransgenic (which we refer to as wild type or WT) and transgenic (which we refer to as genetically modified or GMO) soybean were grown in greenhouse conditions. There were no statistically significant differences in the plant height or biomass of GMO and WT soybean, with or without applied glyphosate.  Metal concentration and intracellular metal distribution were analyzed by synchrotron X-ray fluorescence (sXRF) at beamline 13-ID-E.  Samples of stem and root were prepared for analysis by cryogenic embedding in OCT and sectioned by hand-held microtome.  Sections were preserved by dessication.  Leaves were analyzed in vivo directly sampled off living plants at the time of analysis. All samples were mounted on Kapton film for sXRF analysis.  Although statistically significant reduced levels of calcium were found in leaf vascular and mesophyll tissue in both WT and GMO soybean treated with glyphosate, the leaves of WT soybean sprayed with glyphosate display significantly larger overall decrease in Ca abundance in leaf mesophyll tissue.  It is hypothesized that glyphosate may affect the homeostasis of calcium within the soybean leaf and that the genetic modification that confers glyphosate resistance may partially provide an alternative pathway for Ca incorporation not seen in wild type.

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