Chemical diversity of crop root mucilages: Implications for their maximal water content and decomposition

The biophysical functioning of the rhizosphere can act on plant water use efficiency through root mucilage release and their stimulation of microorganisms' activity. Mucilage characteristics and roles are still poorly studied for the diversity of agronomic plant species. We compared mucilages collected from roots of germinated seeds (aerohydroponics technique) of eight plant species (four Eudicotyledons, four Monocotyledon) in terms of total sugars content, Medium Infrared (MIR) spectra, mucilage maximal water content and induced respiration in contrasting soils. Our results suggest that the "chemical fingerprint" of these mucilages could be discriminated according to the phylogenetic proximity of the plant species. In addition, the maximal water content that mucilage retain seems to be linked to their chemical composition and seems more related to the presence of high molecular weight sugars than their total sugar amounts. If mucilage-induced respiration by soil microbiota appeared to be independent from phylogeny, some mucilages induced more respiration than others regardless of the soil studied. Microbial communities and soil physico-chemical properties interact in decomposition with variations in mucilage's chemical composition.