Variation of the osmotic potential and its effects on water balance in diferente species of bryophytes

ABSTRACT The primitiveness of bryophytes in relation to water balance promotes quick responses. When subjected to conditions of variation in the availability of water in their surroundings. Such responses (resistance or sensitivity to desiccation) can allow them to survive in different types of environments. In this work, the effect of varying the osmotic potential of the medium on the water balance of three species (Campylopus filifolius (Hornsch.) Mitt., Philonotis cernua (Wilson) Griffin & W.R.Buck, Amblystegium varium (Hedw.) Lindb.) of bryophytes was evaluated. For that, specimens (n = 150 gametophytes) were placed in environments (Petri dishes) containing different osmotic concentrations (0 MPa; -0.2 MPa; -0.4 MPa; -0.6 MPa; -0.8 MPa; -1.0 Mpa). As expected, a negative effect of water potential on the water content was observed in the three species evaluated, although each with its own characteristics. Significant differences were found between different species, between different osmotic potentials and over time. C. filifolius was more sensitive to water loss, while P. cernua and A. varium were more resistant. Morphostructural characteristics of each species, probably, were responsible for such responses, which justifies, including the environment of their occurrence (C. filifolius - epiphyte in a highly variable environment in relation to water availability, while P. cernua and A varium - rupicolous near a water source). Thus, the rapid responses in relation to the variation of the osmotic potential of the medium make B. filifolia a species well adapted to water stress conditions.