Halliwell—Asada pathway

The lines of research that led us to believe that elevated levels of the Halliwell-Asada pathway have primary responsibility for increased tolerance to active oxygen are as follows ... 

Table V. Herbicide Cross Tolerances to Oxidative Stresses and Relations with -the Halliwell-Asada pathway...

Figure 5 (A) Evidence that paraquat transiently affects chloroplasts of resistant Conyza and (B) that there are constitutively elevated levels of the Halliwell-Asada active oxygen detoxification pathway in the chloroplasts. A. Resistant and susceptible plants of Conyza bonariensis were sprayed to runoff with 0.1 mM paraquat and whole leaves were removed for measurement of photosynthesis at times thereafter as an estimation of paraquat arriving at, and affecting chloroplasts. Simultaneous measurements of stomatal aperture were made to ascertain that the stomates remained open. Source Data redrawn from (60). B. Normal enzyme levels (without paraquat treatment) in resistant and susceptible Conyza bonariensis. Source Collated and drawn from (57, 61).

Paraquat resistance in Conyza was traced to an elevated level of the Halliwell-Asada enzyme pathway responsible for the degradation of active oxygen species [36]. Resistance in Conyza is controlled by a single dominant nuclear gene that pleiotropically increases the level of the whole pathway [38]. 

Table 1. Herbicide cross tolerances to oxidative stresses and relations with enzymes of the Halliwell-Asada active oxygen detoxification pathway [cf. 36-39]...

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