The Effect of Desiccation on Cation Location in Lichens

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Abstract
Experiments were performed on 15 lichen species from a range of different habitats, to compare the cellular location of cations in desiccation stressed and unstressed material. It was shown that desiccation caused a significant loss of intracellular potassium and magnesium in some species and that the loss can be related to the water availability in the natural habitat. During leakage some immobilization of cations occurs on to the cell wall cation exchange sites. The proportion immobilized depends on the nature of the cation released and the nature of the cations already present on the exchange sites. Desiccation-stressed lichens can partially or wholly recover their original cation distribution by incubation in a humid environment. Desiccation resistance and recovery indices are proposed for lichens. These allow comparisons to be made with bryophytes and conclusions to be drawn about their respective micro-environments.