Date of Graduation

12-2011

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor

Garry V. McDonald

Committee Member

M. Elena Garcia

Second Committee Member

J. Brad Murphy

Third Committee Member

Carl A. Smith

Keywords

Biological sciences, Foliar symptoms, Native plants, Ozone injury, Perennials

Abstract

Twenty seven perennial species native to the Eastern Temperate Forests Level I Ecoregion were exposed to an acute ozone (O3) treatment consisting of a target peak O3 concentration of 2.0 ppm for 30 minutes in a closed chamber environment, during the summer of 2010. Plants were evaluated for visible foliar injury symptoms and symptoms were described and photographically documented. Ten of the 27 species developed visible foliar injury in which interspecific and intraspecific response to O3 was observed. A severity index was used to compare response to acute ozone exposure for the ten species displaying visible foliar injury. Species showing visible foliar injury in descending order of severity index were Coreopsis tripteris L. (tall tickseed), Coreopsis palmata Nutt. (stiff tickseed), Penstemon cobaea Nutt. (cobaea beardtongue), Solidago nemoralis Aiton (gray goldenrod), Monarda fistulosa L. (wild bergamot), Silphium integrifolium Michx (wholeleaf rosinweed), Oligoneuron rigidum (L.) Small var. rigidum (stiff goldenrod), Rudbeckia missouriensis Engelm. ex C.L. Boynt.(Missouri orange coneflower), Penstemon pallidus Small (pale beardtongue), and Solidago speciosa Nutt. (showy goldenrod). A range of symptoms was observed including red to purple stipple and tan to yellow or brown flecking; bronzing, leaf margin necrosis, and bifacial necrotic lesions. Subsequently, in June of 2011, four native Coreopsis species (C. lanceolata, C. palmata, C. tinctoria, and C. tripteris), were exposed to four acute ozone (O3) treatment levels with target peak O3 concentrations of 1.2, 1.7, 2.2, and 2.7 ppm, for 30 minutes in a closed chamber environment. Severity index was used as the criterion for comparing ozone susceptibilities among species. All four species showed foliar injury symptoms following the highest target peak exposure level (2.7 ppm). Two of the four species (Coreopsis palmata and C. tripteris) exhibited foliar injury symptoms at the lowest target peak exposure level (1.2 ppm). Symptoms varied among species in the study but were generally uniform within each taxon. Coreopsis lanceolata showed the highest degree of ozone tolerance relative to the other three species in the study. Both Coreopsis palmata and C. tripteris developed visible foliar symptoms at the lowest treatment level (1.2 ppm) indicating ozone susceptibility relative to the other species.

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