| Abstract: | Eight Hevea species have been shown to be cyanogenic. They all liberated HCN following mechanical tissue injury. Infection of Hevea leaves with conidia of the plant pathogen Microcyclus ulei leads to a large reduction of hydrocyanic acid potential, while only small amounts of HCN are set free from the leaves into the atmosphere. HCN production by infected leaves follows a reproducible pattern with a maximum between 40 and 60 hours after infection. During the entire time of infection free HCN can be detected in the leaves. From leaves of susceptible clones high amounts of HCN are liberated whereas from resistant clones only very little HCN is released. In Hevea infections with M. ulei, cyanogenesis does not lead to defense of the fungal pathogen but impairment of the resistance reaction. |
