Plant cell death and cellular alterations induced by ozone: key studies in Mediterranean conditions.

An account of histo-cytological and ultrastructural studies on ozone effect on crop and forest species in Italy is given, with emphasis on induced cell death and the underlying mechanisms. Cell death phenomena possibly due to ambient O3 were recorded in crop and forest species. In contrast, visible O3 effects on Mediterranean vegetation are often unclear. Microscopy is thus suggested as an effective tool to validate and evaluate O3 injury to Mediterranean vegetation. A DAB-Evans blue staining was proposed to validate O3 symptoms at the microscopic level and for a pre-visual diagnosis of O3 injury. The method has been positively tested in some of the most important crop species, such as wheat, tomato, bean and onion and, with some restriction, in forest species, and it also allows one to gain some very useful insights into the mechanisms at the base of O3 sensitivity or tolerance.