Water movements associated to hydrostatic and osmotic gradients in the storage root of sugar beet (Beta vulgaris).

GABRIELA AMODEO, RICARDO DORR, AUGUSTO VALLEJO, MOIRA SUTKA Y MARIO PARISI.

Vancouver, Canadá

Congreso; Plant Biology 1997 Meeting.; 1997

ASPB

Water is essential for plant growth and development and the recently discovery of water channels (or aquaporins) is opening a new debate whether its role in water movements implies its participation in the overall hydraulic conductivity or is specific for physiological processes such as cell expansion or responses to water stress. The purpose of our work is to understand the role of water channels in water absorption and water movements in root tissues. With this goal we adapted experimental techniques, currently used to study water permeability in animal tissues and monolayers of cultured cells. Tissues sections were mounted as a diaphragm between two barrel Lucite chambers and the measurement of net water flux (Jw) was recorded in real time, minute by minute, in a computer based data acquisition system. Isolated vacuoles of the storage root of sugar beet were studied by following volume changes in response to an osmotic challenge. The root sections were obtained through longitudinal or transversal cuts so that the effect of an hydrostatic (and/or osmotic) pressure could be applied specifically to different sides of the tissue. The chambers were filled with an isoosmotic solution (600 mOsm.kg­-1) in both sides. When an osmotic gradient was needed, solutions were supplemented with 300 mOsm.kg-1 mannitol. In longitudinal sections but not in transversal sections a net water flux increase was observed when an osmotic gradient was applied (p<0.05, n=7). In paired experiments, the effect of mercurial compounds was  studied, and the tissue section was exposed to 1 mM HgCl­­­­2 versus an experimental control. Both Jw before and after 15 min of an applied osmotic gradient were compared to control Jw values. The addition of HgCl2 inhibited the osmotic response (p<0.01, n=7). These results will be compared with those observed in the isolated vacuoles.