Abstract
In order to study the response to water deficit of the moss Racomitrium crispipilum (Taylor) A. Jaeger, a bryophyte typical of open sites and expose to water shortage, measurements of its soluble protein and proline contents, and enzymatic activity of catalase and peroxidase were made. Sampling was done in the Páramo de Chingaza, eastern mountain range of Colombia, in the zone of Lagunas de Buitrago during the dry season. We determined that R. crispipilum diminish its relative water content (RWC) from 50% to 4% of its dry mass (DM) (i.e. to <10% of its capacity), without losing the ability to synthesize proteins in the rehydration. Declining RWC was associated with declining soluble protein content and increased activities of catalase and peroxidase. Enzyme activities peacked in the hours at which R. crispipilum exhibited its minimum RWC (21.02 U mg protein-1 min-1 for catalase and 172.66 for peroxidase). Proline was found to be high during the hours of maximum RWC and the earliest hours of diminishing RWC, between 60 and 87.07 mg g dry mass-1 and declines to 18.98 during the afternoon. The results reported in this study give the first evidence that the activities of catalase and peroxidase increase in this species in response to conditions of water deficit. This is likely to be an important component in the mechanism by which this moss tolerates drought periods.