DIFFERENTIAL INDUCTION OF RESISTANCE AND ENHANCED ENZYME-ACTIVITIES IN CUCUMBER AND TOBACCO CAUSED BY TREATMENT WITH VARIOUS ABIOTIC AND BIOTIC INDUCERS

Systemic-induced resistance was established in tobacco and cucumber pl ants by treatment with various inducers. Extracts from Reynoutria sach alinensis, silica preparations (Hornkiesel P 501), or aspirin, when ap plied 1-3 days before the challenge inoculation, more effectively inhi bited disease development than inducers from bacterial or fungal cultu res. The inducers did not reduce disease development by directly inhib iting the growth of pathogens. Treatment with inducers led to an incre ase in activities of chitinase, beta-1,3-glucanase, peroxidase, polyph enol oxidase, phenylalanine ammonia lyase in cucumber and tobacco leaf tissue and additionally in tobacco to an increase in lysozyme activit y. However, the extent and the time-course of the increase varied acco rding to the inducer and host plant. The increase in resistance and th e activity of particular enzymes were not closely correlated. The time -course of resistance and increased enzyme activities in cumcumber was also correlated with increased formation of papillae in epidermal cel ls.