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Abstract Detail

Integrative Plant Physiology

Hugie, Josie [1], Zhu, Xin-Guang [2], Long, Stephen P. [2], Riechers, Dean [3].

Elucidating the Physiological Mechanism for Mesotrione-Atrazine Synergism in Triazine-Sensitive and Triazine-Resistant Redoot Pigweed (Amaranthus Retroflexus).

Biochemical and physiological overlap of processes affected by the herbicides mesotrione (a hydroxyl-phenylpryruvate dioxygenase (HPPD) inhibitor) and atrazine (a photosystem II inhibitor) have been hypothesized to be responsible for synergism between these two compounds. Potential overlap between mesotrione and atrazine involves competition of atrazine and plastoquinone for the QB binding site in photosystem II (PSII), while mesotrione inhibits the production of plastoquinone and also inhibits the production of protective carotenoids and tocopherols. The objective of this study is to provide insight regarding the mechanism of the interaction between mesotrione and atrazine in both sensitive and site of action-based atrazine-resistant redroot pigweed (Amaranthus retroflexus). First, both herbicides must exist in a leaf simultaneously in order to demonstrate biochemical and physiological overlap of the effected processes. In preliminary studies, chlorophyll fluorescence was used as a non-invasive means to monitor herbicide translocation and herbicide effects over time. Atrazine, which is translocated in the xylem, caused a significant decrease in Fv/Fm within 8 hours in newer leaves but within 2-4 hours in mature leaves. Mesotrione, which is phloem-mobile and accumulates in newly-developing tissue, induced a dramatic decrease in Fv/Fm only in newly-developed leaves between 24 and 48 hours after treatment. When the herbicides are applied together, induction curves will be used to differentiate between the effects of each herbicide within a single leaf. Complementary to Fv/Fm examination, fluorescence induction curves will be used to distinguish unique herbicide signatures and fluorescence imaging will be used to visualize herbicide effects across leaf surfaces.

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1 - University of Illinois, Crop Sciences, N335 Turner Hall MC046, 1102 S. Goodwin Ave, Urbana, Illinois, 61801, United States
2 - University of Illinois, Plant Biology
3 - University of Illinois, Crop Sciences

herbicide joint action
chlorophyll fluorescence
PSII inhibitor
HPPD inhibitor

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P04019
Abstract ID:2132

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