Early defence responses in plants infected with pathogenic organisms.

Plant organisms possess a complex set of defence mechanisms that are responsible for preventing unfavourable interactions with other living organisms in their natural environment or for reducing negative effects of such interactions. They can be classified into two groups: early responses that occur immediately or shortly after contact with a pathogenic organism, usually in the proximity of the infection site, and late, usually transcription- and translation-dependent responses that take part in minimizing the long-term effects of the infection and in preventing further infections. Early responses are a mixture of distinct biochemical processes, leading to quick activation of enzymes, structural changes in components of the living cell, alteration of biochemical pathways and synthesis of intra- and intercellular signals. An important part of early responses are redox processes, especially the synthesis of large amounts of reactive oxygen species.