RESPONSE OF SPIRODELA-INTERMEDIA KOCH,W TO OSMOTICALLY INDUCED WATER SHORTAGE

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.