Identifier

etd-03262009-132122

Degree

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

Document Type

Dissertation

Abstract

Ozone (O3), one of the most powerful oxidants known, is phytotoxic at high levels in the troposphere, or ground-level. Effects of acute ozone exposure for two consecutive days was examined on Bermudagrass (Cynodon dactylon), centipedegrass (Eremochloa ophiuroides), zoysiagrass (Zoysia japonica), St. Augustinegrass (Stenotaphrum secundatum), Liriope muscari ‘Big Blue’, Liriope muscari ‘Aztec’, and Ophiopogon japonicus. Zoysiagrass, St. Augustinegrass, Liriope muscari ‘Big Blue’ were used in the second study based on the differential responses found in the study. Ozone induced severe visual damage to St. Augustinegrass with symptoms appearing as chlorotic streaks. St. Augustinegrass and Liriope muscari had a significant reduction in the maximum quantum yield of PSII electron transport as measured by Fv:Fm ratio, which would indicate no correlation between the visual injury and Fv:Fm. Zoysiagrass and centipedegrass proved to be tolerant to ozone. The objectives of the second study were to evaluate: 1) response to ozone due to cutting; 2) the use of the SPAD-502 chlorophyll meter as an objective measure of ozone-induced injury; 3) xanthophyll cycle involvement in dissipating light energy due to increased oxidative stress; 4) the relationship of chlorophyll fluorescence coefficients, chlorophyll content, and xanthophyll cycle in the regulation and protection of photosynthesis. Cutting had no significance on any of the parameters in this study. Centipedegrass with significantly more â-carotene and a quicker engagement of the xanthophylls cycle than the other species in this study was tolerant to increased ozone. This suggests that closing the stomata to exclude ozone is important but does not repair or detoxify the ozone and/or reactive oxygen species that have already entered the leaf. Visual injury differences in the ozone sensitive St. Augustinegrass may be due to the large thin leaves. Liriope with thick fibrous leaves is sensitive to increased ozone but lacked visual injury.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Edward Bush

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