Abstract: | Buffering capacity and pH values of extracts of pine needles varied with age in the course of the ontogeny of needles. Significant differences between a resistant and a susceptible pine clone group in relation to resistance against Lophodermium pinastri could be shown in autumn and winter. Also the variability of the parasite influences the host-parasite interaction as shown by alteration of pH values by 3 L. pinastri strains in cultural trials on needle extract medium. |