PARENT SESSION
Organized Oral Session 16: Allelopathy: Biochemical interactions among plants affecting community structure, exotic invasions and evolutionary theory
Organizer(s): A Mallik and R Callaway
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal

Measurement of allelochemical dynamics in the rhizosphere.

Weidenhamer, Jeffrey^*,1, ¹ Ashland University, Ashland, OH

ABSTRACT- Polydimethylsiloxane (PDMS) sorbents have been used to trap and quantify the photosynthesis inhibitor sorgoleone exuded into the undisturbed rhizosphere of sorghum-sudangrass plants. Stir bars coated with PDMS (stir bar sorptive extraction), technical grade optical fiber coated with a thin film of PDMS (matrix-solid phase microextraction), and PDMS tubing were buried in pots at planting and removed at 29, 55 and 88 days after planting. As analyzed by HPLC, the amount of sorgoleone recovered increased with time. One barrier to testing hypotheses of allelopathic effects has been the general lack of information on qualitative and quantitative dynamics of allelochemicals in the rhizosphere. When soils beneath suspected allelopathic plants are analyzed, concentrations are typically low, and this has been cited as evidence that these compounds are not important in plant-plant interactions. However, static concentrations in the environment reflect the current balance of input vs. output rates for a compound. Because plant roots compete with microorganisms and other processes that remove allelochemicals from soil solution, flux rates are likely to be a key component of toxicity. PDMS probes may provide an inexpensive, non-destructive method for analyzing allelochemical dynamics in soil. Information on chemical dynamics in the rhizosphere is crucial for evaluating specific hypotheses of allelopathic effects, understanding allelopathic mechanisms and assessing the importance of allelopathic processes in plant communities. Work is ongoing to optimize parameters for the use of PDMS, evaluate its potential as a sorbent for a broad range of allelochemicals in soil, and employ PDMS probes in the field.

Key words: Allelopathy, rhizosphere, analysis, sorgoleone