The aim of this work was to study the response of the aquatic plant Sp
irodela intermedia W. Koch to osmotically-induced water shortage, caus
ed by the inclusion of polyethylene glycol (PEG) in the nutrient solut
ion. Osmotic potentials under -0.60 MPa were lethal for S. intermedia,
-0.40 MPa inhibited vegetative reproduction, -0.20 and -0.10 MPa redu
ced and -0.06 and -0.04 MPa enhanced frond multiplication. Osmotic pot
entials ranging between -0.04 and -0.20 MPa increased the number of fr
onds per colony. Frond surface area declined at -0.10 and -0.20 MPa. P
EG treated fronds diminished their water content. Neither epidermal ce
ll and stomatal frequency nor stomatal size were affected by the reduc
ed water potentials. Mesophyllic cell arrangement changed when plants
grew in PEG-containing nutrient solution.