Peroxidase activity and peroxidase isoenzyme composition in self-pollinated, cross-pollinated and unpollinated styles of Nicotiana alata

By means of starch gel electrophoresis and peroxidase assays a detailed analysis was made of changes in peroxidase activities and variations in peroxidase isoenzyme composition in selfpollinated, cross-pollinated and unpollinated styles of the self-incompatible species Nicotiana alata. Pollination and subsequent pollen tube growth cause an increase of the total peroxidase activity and of several peroxidase isoenzymes. This increase is more pronounced in cross- than in self-pollinated styles, especially after four days when many compatible growing pollen tubes have reached the ovules. During the progamic phase only one clear difference was observed between the isoenzyme patterns of self- and cross-pollinated styles. One of the new peroxidases only appeared after cross-pollination. The significance of the observed differences is discussed in relation to the incompatibility reaction. The results are compared with data on changes in peroxidase activity after fungal infection in plant hosts.