Long-term responses of the green-algal lichen Parmelia caperata to natural CO2 enrichment

L Balaguer; E Manrique; A de Los Rios; C Ascaso; K Palmqvist; M Fordham; J D Barnes

doi:10.1007/s004420050773

Long-term responses of the green-algal lichen Parmelia caperata to natural CO₂ enrichment

Oecologia. 1999 May;119(2):166-174. doi: 10.1007/s004420050773.

Authors

L Balaguer¹, E Manrique², A de Los Rios³, C Ascaso³, K Palmqvist⁴, M Fordham⁵, J D Barnes⁵

Affiliations

¹ Departamento de Biología Vegetal I, Facultad de Biología, Universidad Complutense, Madrid, E-28040, Spain e-mail: balaguer@eucmax.sim.ucm.es, Tel.: +34-1-3945047, Fax: +34-1-3945034, , , , , , ES.
² Departamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense, Madrid, E-28040, Spain, , , , , , ES.
³ Centro de Ciencias Medioambientales (CSIC), Serrano 115 dup., Madrid, E-28006, Spain, , , , , , ES.
⁴ Department of Plant Ecology, Umeå University, S-90187 Umeå, Sweden, , , , , , SE.
⁵ Air Pollution Laboratory, Department of Agricultural and Environmental Science, Ridley Building, The University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK, , , , , , GB.

PMID: 28307965
DOI: 10.1007/s004420050773

Abstract

Acclimation to elevated CO₂ was investigated in Parmelia caperata originating from the vicinity of a natural CO₂ spring, where the average daytime CO₂ concentration was 729 ± 39 μmol mol^-1 dry air. Thalli showed no evidence of a down-regulation in photosynthetic capacity following long-term exposure to CO₂ enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate carboxylase/oxygenase (Rubisco) content, apparent quantum yield of CO₂ assimilation, and the light-saturated rate of CO₂ assimilation (measured under ambient and saturating CO₂ concentrations) were similar in thalli from the naturally CO₂ enriched site and an adjacent control site where the average long-term CO₂ concentration was about 355 μmol mol^-1. Thalli from both CO₂ environments exhibited low CO₂ compensation points and early saturation of CO₂ uptake kinetics in response to increasing external CO₂ concentrations, suggesting the presence of an active carbon-concentrating mechanism. Consistent with the lack of significant effects on photosynthetic metabolism, no changes were found in the nitrogen content of thalli following prolonged exposure to elevated CO₂. Detailed intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae located in the elongation zone of thalli originating from elevated CO₂, an effect associated with a reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced limitations to CO₂ assimilation in lichens originating from the CO₂-enriched site. The light-saturated rate of CO₂ assimilation measured at the average growth CO₂ concentration was found to be significantly lower in thalli originating from a CO₂-enriched atmosphere compared with that of thalli originating and measured at ambient CO₂. At lower photosynthetic photon flux densities, the light compensation point of net CO₂ assimilation was significantly higher in thalli originating from elevated CO₂, and this effect was associated with higher usnic acid content.

Keywords: Key words Elevated CO2; Lichenized green algae; Photobiont ultrastructure; Photosynthetic performance; Rubisco.