Resistance of mosses to drying, measured by the intensity of gas exchange and the content of malate and citrate

Desiccation tolerance, the ability to lose virtually all of its free intracellular water and then restore normal function when rehydrated, is one of the most remarkable features of bryophytes. The aim of the study was to determine the resistance of two species of Plagiomnium undulatum (Hedw.) T.J.Kop. and Polytrichum commune Hedw. on drying to 50% relative water content of the air and rehydration. Changes in the intensity of photosynthesis and respiration as well as the content of malate and citrate in leafy moss stems were analysed. P. commune gametophores showed greater resistance to drought stress than P. undulatum. In both species, photosynthesis was much more sensitive to drought than respiration. Changes in the content of malate and citrate indicated a high plasticity of moss metabolism in conditions of water shortage and may be one of many important elements of the adaptation strategy to water deficit. The reactions of the tested mosses to dehydration and rehydration confirmed their adaptation to specific land conditions.