Induction of disease resistance in plants by heat-shock

The fungus Cladosporium cucumerinum infects cucumber and causes disease in the plant. However, if seedling of cucumber is immersed in water at 50° C for 40 seconds prior to experimental inoculation with the fungus, the disease symptoms are reduced by 60%. Resistance develops in 24 to 30 hours after the hot water treatment and remains effective for at least 2 days. One of the earliest observable effects of this treatment is a rise in ethylene production. Soluble peroxidase enzyme associated with the cucumber cell wall also increases in close correlation with the increase in resistance.