Absorption, translocation and metabolism of pyridate in chickpea (Cicer arietinum)

This work studied the tolerance mechanisms of chickpea (Cicer arietinum L.) to pyridate, a post-emergence herbicide used in other crops such as maize, peanut and wheat. Foliar absorption of pyridate in chickpea was limited and occurred mainly during the first 24 h after treatment. Over 83% of the herbicide absorbed remained in the treated leaf 72 h after treatment. Twelve hours after herbicide treatment, 50% of the total herbicide applied was converted to CL9673-N-Gly, an intermediate metabolite essential in the activation of the pyridazine ring for following conjugations. The N-glycoside was conjugated to form more-polar metabolites, C1 and C2: C1 was identified as CL9673-N-Gly-glutathione; and C2 was identified as CL9673-N-Gly-cysteine. C1 appeared 3 h after treatment and reached a maximum of around 40% of recovered radioactivity 72 h later, while C2 appeared 24 h after treatment and reached a maximum of 10% 72 h later. Chickpea glutathione transferases do not seem to be involved in the formation of C1, thus the final amount of this conjugate mainly depends on the amount of N-glycoside formation in vivo.