Decomposition in soil and chemical changes of maize roots with genetic variations affecting cell wall quality

Summary Roots of brown-midrib (F2bm1 and F292bm3) maize mutants and their normal isogenic counterparts (F2 and F292) were used to evaluate the changes in chemical cell wall features with regard to polysaccharides, lignin composition and interconnecting phenolic acids during root degradation in soil. To this end, the chemical variability of roots of brown-midrib mutants and their normal counterparts was compared and its subsequent impact on carbon (C) mineralization determined under controlled conditions. The bm1 mutation mainly caused an increase in lignin content and a decrease in polysaccharide content of maize roots whereas the bm3 mutation caused only a decrease in polysaccharide content. The lignin composition of bm roots differed from that of normal lines and the proportion of cell wall ester-linked hydroxycinnamic acids was also different. C mineralization kinetics differed markedly between the genotypes. Certain relevant factors concerning root decomposition in soil were studied from the relationships between the chemical characteristics of maize roots at different stages of decomposition and C mineralization rates. The Klason lignin-to-glucose ratio (KL/Glu), the Klason lignin-to-arabinoxylans ratio (KL/AX) and the arabinose-to-xylose ratio (A/X) were proposed as promising predictive indicators of C mineralization kinetics. Future estimations of soil residue decomposition could be improved by taking these initial chemical criteria into account on a wider range of residues.