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Abstract Detail


Environmental Physiology

Rudrappa, Thimmaraju [1], Justin, Bonsall [2], Gallagher, John L. [3], Seliskar, Denise M. [4], Harsh, Bais [5].

Root-secreted allelochemical in the noxious weed Phragmites australis deploys a reactive oxygen species response and microtubule assembly disruption to execute rhizotoxicity.

An experimentally proven phenomenon described as “novel weapons hypothesis” (NWH) relates to the growth suppression of the native species by secretion or production of allelochemicals from exotic and introduced plants. Phragmites australis is considered the most invasive plant in marsh and wetland communities in the eastern United States. Although, allelopathy was superficially suggested as the main displacing mechanism in P. australis, there has been minimal success in characterizing the responsible allelochemical. We tested the occurrence of NWH in the invasion of P. australis. To this end, the root exudates of two P. australis genotypes, BB (native) and P38 (an exotic) were tested for phytotoxicity on different plant species. The treatment of P. australis root exudates on the susceptible plants resulted in acute rhizotoxicity. The root exudates of P38 were more effective in causing root death in susceptible plants compared to the native BB exudates. The active ingredient in the P. australis exudates was identified as 3,4,5-trihydroxybenzoic acid (Gallic acid: hereafter GA). We tested the phytotoxic efficacy of GA on various plant systems including the model plant Arabidopsis thaliana. Most of the tested plants succumbed against the GA treatment with an exception of P. australis itself. Mechanistically, GA treatment generated elevated levels of reactive oxygen species (ROS) in the treated plant roots. Further, the triggered ROS mediated the disruption of the root architecture of the susceptible plants by damaging the microtubule assembly. The present study also showcases the involvement of in soil growth inhibitory effects of P. australis against A. thaliana with the increased persistence of the exuded GA in the P. australis’s rhizosphere.


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1 - University of Delaware, Delaware Biotechnology Institute, Department of Plant and Soil Sciences, 15 Innovation Way, Newark, DE, 19711, USA
2 - University of Delaware, Delaware Biotechnology Institute,, Department of Plant and Soil Sciences
3 - University of Delaware College of Marine and Earth Studies, University of Delaware College of Marine and Earth Studies, 700 Pilottown Road Lewes, Delaware 19958.
4 - University of Delaware, University of Delaware College of Marine and Earth Studies, 700 Pilottown Road Lewes, Delaware 19958.
5 - University of Delaware, Delaware Biotechnology Institute,, Department of Plant and Soil Sciences, 15 Innovation Way, Newark, DE, 19711, USA

Keywords:
Phragmites australis
root exudation
allelopathy
gallic acid
reactive oxygen species
microtubule.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P01023
Abstract ID:991


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