Mineral Uptake and Release by Lichens: An Overview

Background and enhanced levels of elements in lichens are re- viewed, and the Fe/Ti content ratio is shown to reflect the presence of trapped particulates. The following uptake and release mechanisms are critically ex- amined: extracellular ion-exchange processes, extracellular electrolyte sorp- tion, particulate trapping and subsequent solubilization, metal hydrolysis, intracellular uptake and release and the rewetting and 'resaturation respira- tion' phases. A brief survey of the nutritional requirements and nutritive value of lichens is also provided. Finally, it is concluded, after an examination of the mineral sources available to lichens and of mineral translocation and turnover rates in lichen thalli and mats, that lichen morphology and physi- ology favor their participation in mineral cycling.