Metribuzin herbicide induced a defense mechanism in normal and NaCl-stressed castor bean and maize plants

摘要

Indices of stress including changes in activity of phenylalanine -ammonia lyase, (PAL) and tyrosine ammonia lyase; (TAL) as well as the contents of ascorbate (ASA), glutathione (GSH) and anthocyanin pigment, were determined in metribuzin and NaCl-treated Ricinus communis and Zea mays plants. Addition of 0.5 #mu#g centrd dot g~(-1) and 2.5 #mu#g centre dot g~(-1) of metribuzin into Hoagland nutrient media, either alone, or in combination with NaCl, induced significant decreases in PAL and TAL activities, whereas significant increases in these activities were apparent in castor bean and maize seedlings and plants treated with high concentrations (5 and 10 #mu#g centre dot g~(-1)) of the herbicide, again either alone or in combination with NaCl. Thecontents of anthocyanin, ascorbic acid and glutathione of both castor bean and maize seedlings (7-day-old) and plants (25-day-old) treated with low concentrations of herbicide, either alone or supplemented with NaCl, were significantly decreased, whereasat high concentrations of the herbicide a significant increase in these indices of stress was found.