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Allelopathy Journal
Year : 2009, Volume : 23, Issue : 1
First page : ( 85) Last page : ( 94)
Print ISSN : 0971-4693. Online ISSN : 0973-5046.

Identification of pollen allelochemical in Hieracium x dutillyanum Lepage and its ecological impacts on Conyza canadensis (L.) Cron. and Sonchus arvensis L. dominated community in southern Ontario, Canada

Murphy Stephen D.*, Flegel Sherri, Smedes Joanna, Finney Nigel, Zhang Beipeng, Walton Katharina, Henstra Steve

Department of Environment and Resource Studies, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.

*Correspondence Author: E-mail: sd2murph@uwaterloo.ca

Revised:  11  November,  2008.

Abstract

During repeated and long term experiments using in vitro and field tests, we examined the identity of the pollen allelochemical in Hieracium x dutillyanum Lepage & its ecological impacts on a Conyza canadensis and Sonchus arvensis dominated community in southern Ontario, Canada. We found that H. x dutillyanum had significant numbers of pollen grains transmitted to both Conyza canadensis and Sonchus arvensis in the field. Further, we determined that the field impacts matched the in vitro tests and that the number of pollen grains or equivalent extract concentrations was ecologically relevant. We confirmed that the chemical responsible for the pollen allelopathic effect is phenylacetic acid - similar to Ana Luisa Anaya lab's finding for a cultivar of Zea mays. During 1997–2008, flowering populations of H. x dutillyanum caused declines in populations of both Conyza canadensis and Sonchus arvensis. In contrast, if we manipulated fields by bagging H. x dutillyanum inflorescences, then the populations of Conyza canadensis and Sonchus arvensis rose significantly during this time period. Because the fields were otherwise similar and not manipulated further, we conclude that the long-term population responses in Conyza canadensis (L.) Cron. and Sonchus arvensis L. are explained solely by the presence or absence of allelopathic pollen (using phenylacetic acid) from Hieracium x dutillyanum. This is the first comprehensive and long term study examining the identity of the pollen allelopathic chemical, the in vitro response, the in situ response, and the population and community responses.

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Key words

Hieracium x dutillyanumConyza canadensisSonchus arvensis, pollen allelopathy.

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