Effects of elevated CO2 and O3 on aspen clones of varying O3 sensitivity

Autor: Asko Noormets, Jaak Sober, Elina Oksanen, David F. Karnosky, B. A. Wustman, J. G. Isebrands, George R. Hendrey, Kurt S. Pregitzer, G. K. Podila
Rok vydání: 2003
Předmět:
DOI: 10.1016/s1474-8177(03)03022-5
Popis: To determine whether elevated CO 2 reduces or exacerbates the detrimental effects of O 3 on aspen ( Populus tremuloides Michx.). Aspen clones 216 and 271 (O 3 tolerant), and 259 (O 3 sensitive) were exposed to ambient levels of CO 2 and O 3 or elevated levels of CO 2 , O 3 , or CO 2 + O 3 in the FACTS II (Aspen FACE) experiment, and physiological and molecular responses were measured and compared. Clone 259, the most O 3 -sensitive clone, showed the greatest amount of visible foliar symptoms as well as significant decreases in chlorophyll, carotenoid, starch, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) concentrations and transcription levels for the Rubisco small subunit. Generally, the constitutive (basic) transcript levels for phenylalanine ammonia-lyase (Pal) and chalcone synthase (Chs) and the average antioxidant activities were lower for the ozone sensitive clone 259 as compared to the more tolerant 216 and 271 clones. A significant decrease in chlorophyll a, b and total (a+b) concentrations in CO 2, O 3 , and CO 2 + O 3 plants was observed for all clones. Carotenoid concentrations were also significantly lower in all clones; however, Chs transcript levels were not significantly affected, suggesting a possible degradation of carotenoid pigments in O 3 -stressed plants. Antioxidant activities and Pal and 1-aminocyclopropane-1-carboxylic acid (ACC)-oxidase transcript levels showed a general increase in all O 3 treated clones, while remaining low in CO 2 and CO 2 + O 3 plants (although not all differences were significant). Our results suggest that the ascorbate-glutathione and phenylpropanoid pathways were activated under ozone stress and suppressed during exposure to elevated CO 2 . Although CO 2 + O 3 treatment resulted in a slight reduction of O 3 -induced leaf injury, it did not appear to ameliorate all of the harmful affects of O 3 and, in fact, may have contributed to an increase in chloroplast damage in all three aspen clones.
Databáze: OpenAIRE