Role of active oxygen species and NO in plant defence responses

Research in the area of active oxygen species is going through a reflective stage. There is controversy whether multiple mechanisms for active oxygen species generation exist and some data may need reassessing since the disco very of a role for NO in defence responses. Important work concerning upstr eam and downsteam signalling in this area is emerging, and the stage is set for approaches utilising transgenic knockouts and mutants to resolve many questions.