Ultrastructural changes in Spirodela intermedia in response to osmotically-induced water shortage

The ultrastructural changes produced in the upper mesophyl cells of Spirode la intermedia W. Koch, by the inclusion of polyethylene glycol (PEG) in the nutrient solution, are related to the degree of the osmotically-induced wa ter shortage. The ultrastructural characteristics of the -0.08 MPa treated fronds differed from the untreated ones in the form of the chloroplasts. PE G up to -0.20 MPa induced considerable cell structural disorganization as t he swelling, breaking and disappearance of the outer membrane of the chloro plasts and the breakdown of the tonoplast into small vesicles.