Potential effects of rising tropospheric concentrations of CO2 and O3 on green-algal lichens

• Published in: The New phytologist 1996-04, Vol.132 (4), p.641-652
• Main Authors: Balaguer, L, Valladares, F, Ascaso, C, Barnes, J.D, Rios, A. de los, Manrique, E, Smith, E.C
• Format: Article
• Language: English
• Subjects: air pollution; Animal, plant and microbial ecology; Applied ecology; assimilation; Biological and medical sciences; carbon dioxide; carbon dioxide enrichment; cell ultrastructure; chlorophyll; chloroplasts; density; dose response; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Elevated CO2; elevated O3; fluorescence; Fundamental and applied biological sciences. Psychology; lichens; lipids; localization; Metabolism; mycobionts; ozone; Parmelia; parmelia sulcata; phenolic acids; photobionts; photosynthesis; Photosynthesis, respiration. Anabolism, catabolism; photosynthetic capacity; Plant physiology and development; pollutants; pyrenoblobuli; pyrenoids; respiration rate; ribulose-bisphosphate carboxylase; starch; ultrastructure
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.1996.tb01882.x

summary Pormelia 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’ [350μmol mol−1] and ‘elevated’ [700μmol mol−1] 24 h d−1) and two O3 regimes (‘non‐polluted’ air [CF, < 5 nmol mol−1] and ‘polluted’ air [15 nmol mol−1overnight 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 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 CO2and/or O3 was accompanied by a parallel decrease in the concentration of Rubiscoa 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 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 II photochemistry, 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 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.