You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Potential Effects of Rising Tropospheric Concentrations of CO2 and O3 on Green-Algal Lichens
Luis Balaguer, Fernando Valladares, Carmen Ascaso, Jeremy D. Barnes, Asuncion de Los Rios, Esteban Manrique and Elizabeth C. Smith
The New Phytologist
Vol. 132, No. 4 (Apr., 1996), pp. 641-652
Stable URL: http://www.jstor.org/stable/2558883
Page Count: 12
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
Parmelia sulcata Taylor was used as a model to examine 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' [350 μmol mol-1] and `elevated' [700 μmol mol-1] 24 h d-1) and two O3 regimes (`non-polluted' air [CF, < 5 nmol mol-1] and `polluted' air [15 nmol mol-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 assimilation (Asat) measured at ambient CO2 by 30% and 18%, respectively. However, despite this effect ultrastructural 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 Rubisco in the algal pyrenoid (r = 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 O3 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 II photochemistry, and enhanced starch accumulation in the photobiont over the fumigation period, the study shows that the green-algal lichen symbiosis might be influenced by future changes in atmospheric composition. Photosynthetic capacity, measured at ambient CO2, was found to be reduced after a controlled 30 d exposure to elevated CO2 and/or O3 and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal chloroplasts.
The New Phytologist © 1996 New Phytologist Trust