PARENT SESSION
Contributed Oral Session 28: Plant Physiology: Effects of Ozone CO2, and Cavitation
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal
Reduced reproductive effort in ozone sensitive cutleaf coneflower (Rudbeckia laciniata var. digitata) clones in Great Smoky Mountains National Park.
Neufeld, Howard*,1, Woods, Melissa1, Davison, Alan2, Chappelka, Arthur3, Burkey, Kent4, Sachs, Susan6, 1 Appalachian State University, Boone, NC2 University of Newcastle-Upon-Tyne, Newcastle, UK3 Auburn University, Auburn, AL4 USDA-ARS Air Quality Research Unit, Raleigh, NC6
ABSTRACT- ®Ozone is the most important gaseous pollutant in Great Smoky Mountains National Park, and may cause foliar injury on nearly 6% of the flora in the Park. For the past five years, we have been studying the impacts of ozone in the Park on cutleaf coneflower (Rudbeckia laciniata var. digitata) and have documented the presence of foliar injury in the field that correlates with decreases in photosynthesis and stomatal conductance. Populations of coneflower are comprised of sensitive and insensitive individuals, with sensitive plants developing foliar injury earlier in the season, and to a greater extent by the end of the season. In 2004, we measured reproductive effort in 20 sensitive and 20 insensitive individuals at the Appalachian Highlands Science Learning Center at Purchase Knob, near Waynesville, NC. Sensitive plants produced 36% fewer flower heads than insensitive plants (5.35 vs 8.60, p < 0.01), 52% fewer seeds per plant (153 vs 101, p < 0.001), and 29% less seed mass (0.20 vs 0.28, p < 0.001). Mean seed weights did not differ between the groups (0.002 g). Thus, sensitive plants had greatly reduced reproductive effort compared to insensitive plants. Two nonexclusive hypotheses arise from these results: (1) sensitive plants may have intrinsically lower reproductive effort than insensitive plants, even in the absence of ozone, and (2) reproductive effort in sensitive plants is reduced more by ozone than for insensitive plants. Field studies of reproductive effort in filtered vs ambient air will eventually be needed to distinguish between these two hypotheses.
Key words: Rudbeckia laciniata, Ozone, Smoky Mountains, Reproduction