PARENT SESSION
Poster Session #19: Invasive Species Ecology: Deserts and Rangelands.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Influence of moisture and temperature on African rue (Peganum harmala) germination.
Lepak, Dominika*,1, Abbott, Laurie1, 1 New Mexico State University, Las Cruces, NM
ABSTRACT- African rue (Peganum harmala) is a suffrutescent shrub native to the Middle East. Originally introduced to North America in the 1920s at Deming, New Mexico, populations are now reported in New Mexico, Arizona, Texas, California, Nevada, Montana, Oregon, and Washington. Control and management are warranted because this species appears to dominate in most areas where it occurs. Little is known about African rue biology and ecology. Our preliminary data indicate that 1) seeds germinate readily at water potentials greater than −0.5MPa, but germination has not been observed at lower water potentials, and 2) germination rates increase as temperature increases from 22 to 32°C. We report results of two experiments investigating moisture and temperature effects on germination of African rue seed collected from two populations in southern New Mexico. In the first experiment, seeds will be exposed to three temperatures (15, 25, and 35°C) and five water potential levels ranging from 0 to −0.5MPa. A second experiment tests the effects of seed priming on germination. Seeds are exposed to subgermination matric potentials (−1MPa, −1.5MPa, −2MPa, and −4MPa) for 48 hours, subsequently dried, and rewetted at water potential levels at which seeds germinate (0MPa and −0.3MPa). In both experiments water potential levels are manipulated using varied concentrations of polyethylene glycol (PEG) solutions; seeds are suspended on dialysis membrane at the solution surface. Response variables are total percent germination, germination rate, and time to 50% germination. Both experiments are being conducted in a controlled environment chamber and will be concluded in June 2002. Results of these experiments will enable prediction of moisture and temperature conditions conducive to significant African rue seed germination events. This information is necessary to develop strategies to manage this invasive species.
KEY WORDS: invasive species