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Potential effects of rising trpopheric concentrations of CO2 and O=3 on green-algal lichens

AuthorsBalaguer, L.; Valladares Ros, Fernando ; Ascaso, Carmen ; Barnes, J. D.; Ríos, Asunción de los ; Manrique, Esteban ; Smith, Elizabeth C.
KeywordsElevated CO2
Elevated O3
Photosynthetic capacity
Issue Date1996
PublisherBlackwell Publishing
CitationNew Phytologist 132(4): 641-652 (1996)
AbstractPormelia sulcata Taylor was used as a model to examinate the effects of elevated CO2 and/or O3 on green algal lichens. Thalli were exposed for 30 d in duplicate controlled-environment chambers to two atmospheric concentrations of CO2 ("ambient" (350umol mol-1) and "elevated" (700umol mol-1) 24 h d-1) and two O3 regimes ("non-polluted" air (CF, menos 5nmol mol-1) and polluted" air (15 nmoi mo-1 overnight rising to a midday maximum of 75 nmol mol-1)), in a factorial design. Elevated CO2 or elevated O3 depressed the light saturated rate of CO2, assmilitaion Asat) measured at ambient CO2, by 30% and 18%, respectively. However, despite this effect ultrastructure) studies revealed increased lipid storage in cells of the photobiont in response to CO2-enrichment. Simultaneous exposure to elevated O3 reduced CO2-induced lipid accumulation and reduced Asat in an additive manner. Gold-antibody labelling revealed that the decline in photosynthetic capacity induced by elevated CO2 and/or O3 was accompanied by a parallel decrease in the concentration of Rubiscoa in the algal pyrenoid (I=.0.93), interestingly, differences in the amount of Rubisco protein were not correlated with changes in pyrenoid volume. Measurements of in vivo chlorophyll-fluorescence induction kinetics showed that the decline in Asat induced by elevated CO2, and/or O2, was not associated with significant changes in the photochemical efficiency of photosystem (PS) II. Although the experimental conditions inevitably imposed some stress on the thalli, revealed as a significant decline in the efficiency of PS IIphotochemistry, and enhanced starch accumulation in the photobiont over the fornication period, the study shows that the green-algal lichen symbiosis might be influenced by future changes in atmospheric composition. Photosynthetic capacity, measured et ambient CO2, was found to be reduced after a controlled 30 d exposure to elevated CO2, and/O3 and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal choroplasts.
Description12 pages, figures, and tables statistics.
Appears in Collections:(ICA) Artículos
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