Phenology, morphology, aboveground biomass and root-associated soil respiration of Arabidopsis thaliana down-regulated cell wall mutants of MYB75, KNAT7, and CCR1

Abstract

Abstract The growth pattern (phenology), resource allocation (morphology) and biomass accumulation of plant above-ground components is expected to have a feedback on root-associated processes in soil like water uptake, nutrient cycling and gas production. The aim was to see how above-ground plant characteristics (phenology, morphology and biomass) would impact water depletion, mineral nitrogen (N) concentration and carbon dioxide (CO2-C) and nitrous oxide (N2O-N) production from root-associated soil of Arabidopsis thaliana lines (wild ecotypes and down regulated mutants of MYB75, KNAT7 and CCR1 having altered lignin concentration in secondary cell walls) at various plant developmental stages. Phenology and morphology were determined on A. thaliana lines grown to maturity in peat moss-based substrate under controlled conditions. Plant biomass, water use, soil mineral N concentration and root-associated soil respiration were measured at various growth stages of A. thaliana lines grown in un-drained plastic pots containing clay-loam soil. The CCR1 mutant line had delayed maturation. While MYB75 and KNAT7 had similar morphology as the wild ecotype, the CCR1 line had fewer and smaller viable fruits, less crown cover of rosette leaves and lower biomass than the wild ecotype. The CCR1 mutant line had lower evapotranspiration than the wild ecotype. Respiration of root-associated soil planted with MYB75 and KNAT7 was similar to the wild ecotype. Higher N2O production from soil planted with CCR1 was attributed to higher soil moisture content and mineral N concentration of bulk and rhizosphere soil than the wild ecotype. Morphology and biomass exerts strong influence on water content, mineral N concentration and soil respiration. Due to prolonged vegetative growth phase, reduced fecundity and biomass, the CCR1 mutant lowered evapotranspiration and left more mineral N in root-associated soils, which explained the higher N2O emission from soil during its growth and development.