Enzymatic and biochemical alterations in relation to lignin deposition at different growth stages of tall fescue

Abstract

Lignin is a phenolic biopolymer that limits the intake potential and energy availability of forage crops. In order to understand the lignification process, enzymatic and biochemical studies were conducted at four different growth stages of tall fescue (Festuca arundinacea Schreb.). An increase in phenylalanine ammonia lyase and tyrosine ammonia lyase activity was observed with advancement of growth from first node palpable stage to third node palpable stage with a decrease at spikelet emergence stage. Cinnamoyl-CoA reductase and peroxidase exhibited a continuous significant (p < .05) increase and positive correlation with lignin concentration. Cinnamyl alcohol dehydrogenase exhibited a significant (p < .05) positive correlation with lignin concentration, suggesting its probable exclusive role in tall fescue lignification. Cellulose and total phenol exhibited a 13.0 and 71.8% increase, whereas pectin and crude protein exhibited a significant (p < .05, p = .0001) decrease of 65.1 and 15.4%, respectively, with the growth advancement from first node palpable to spikelet emergence stage. Klason lignin also exhibited a dramatic 9.4-fold increase from vegetative to reproductive stage. The enzymatic and biochemical alterations were closely associated with the lignification process. This study provides an integrated picture of the enzymatic and biochemical alterations that accompany changes in lignin deposition in tall fescue. INTRODUCTIONLignin (Latin word lignum meaning "wood"), a phenolic polymer, is one of the major components of forage cell walls and accounts for 30% of total organic carbon content of the biosphere (Liu et al., 2018). Lignin exists as undigestible lignocellulosic biomass and is an inhibitor of cell