Scientists' Contributions

Copper impact on lichen physiology

Cristina Branquinho¹, Dennis H. Brown² and Fernando Catarino¹

    The role of lichens as sensitive indicators and monitors of atmospheric pollution is of undeniable importance. Despite the great number of publications dealing with the interaction of lichens with heavy metals, a detailed knowledge on the physiology of metal absorption in these organisms, i.e. uptake, accumulation, retention, localisation, release, tolerance and toxicity of metals, is needed before lichens can be extensively and reliably used for monitoring metal deposition patterns .

    In this abstract a critical review of the more pertinent aspects of the interaction between lichens and metals, will be discussed with emphasis on: effects of metals on physiological performance; their tolerance mechanisms; uptake and location of metals.

    Under field conditions, metals are delivered to the lichens dissolved in precipitation and in particulate form. Until now, only a few in practical biomonitoring studies using lichens have discriminated between soluble and insoluble metals, as well as intra- and extracellular location of the soluble metals. In this presentation some of data concerning metals in lichens in particulate and soluble will be presented and related to probable sources.

    The data in this work supported the hypothesis that the absence of the lichen Ramalina fastigiata near copper mine site was related with toxic levels of Cu-dust near the centre of the mine. Total inhibition of PSII photochemical reactions occurred in R. fastigiata both under field and controlled conditions, when intracellular Cu concentrations exceeded a threshold of ca. 2.0 æmol g-1. No samples of this species were found under field conditions beyond the Cu threshold, suggesting that the absence of the lichen R. fastigiata might be used as an indicator of intracellular Cu concentrations above 2.0 æmol g-1 in the surroundings of the copper-mine. The intracellular location of Cu allowed to explain the physiological changes and the survival of the species in the surroundings of the copper-mine.