ECOLOGICAL PHYSIOLOGY OF THE LICHEN HYPOGYMNIA PHYSODES

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Abstract
SUMMARY: The effect of constant saturation with water upon Hypogymnia physodes for periods of up to 7 days was investigated in either light or dark, at either 20°C (representative of most laboratory experiments on lichen physiology) or 5°C (more representative of field conditions). In all cases the capacity for photosynthesis, phosphate uptake, and total polyol content declined over 7 days; the decline was greater at 20°C than 5°C, and usually greater in the dark than in the light. In general, both alga and fungus reacted similarly to the treatments.Previously fixed 14C mostly remained in the polyol pool during the treatments, with relatively little entering the insoluble fraction. The substantial loss of previously fixed 14C during 7 days saturation was almost entirely from the methanol soluble fraction. Within the insoluble fraction, there was also no loss of 14C during the 7‐day period if protein had been previously labelled with 14C‐leucine.Two other lichens, Xanthoria aureola and Peltigera horizontalis, also showed broadly similar declines to Hypogymnia physodes in various physiological characteristics.