Lignification and related enzymes in Glycine max root growth-inhibition by ferulic acid

Changes in soluble and cell wall bound peroxidase (POD, EC 1.11.1.7) activity, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity, and lignin content in roots of ferulic acid-stressed soybean (Glycine max (L.) Merr.) seedlings and their relationships with root growth were investigated. Three-day-old soybean seedlings were cultivated in half-strength Hoagland nutrient solution containing 1.0 mM ferulic acid for 24-72 hr. Length, fresh weight, and dry weight of roots decreased, while soluble and cell wall bound POD activity, PAL activity, and lignin content increased after ferulic acid treatment. These enzymes probably participate in root growth reduction in association with cell wall stiffening related to the formation of cross-linking among cell wall polymers and lignin production.