Physico-chemical properties of maize (Zea mays L.) mucilage differ with the collection system and corresponding root type and developmental stage of the plant

Purpose: Mucilage plays crucial roles in root-soil interactions. Collection systems for maize (Zea mays L.) use primary and seminal roots of aeroponically-grown seedlings (CS_A), or brace roots of soil-grown plants (CS_B). While each method represents specific plant developmental stages, and root types growing in specific (micro-)environments, these factors are rarely considered. It is unclear whether mucilage exhibits distinct physico-chemical properties related to collection system-inherent factors. Methods: Mucilage of maize genotype B73 was collected from systems CS_A and CS_B. Chemical composition was assessed by pH, nutrient contents, neutral sugar composition, and polysaccharide polymer length. Viscosity, surface tension and contact angle represented physical properties. Results: The share of hexoses among total polysaccharides was 11% higher in CS_B than in CS_A, whereas pentoses were predominant in CS_A, together with higher nutrient concentrations and pH values. Mannose was detected only in CS_B, which also exhibited higher surface tension, viscosity and contact angle compared to CS_A. Conclusions: Physico-chemical differences between the two mucilages are related to root type functions, environmental root growth conditions, and plant developmental state. Higher fractions of pentoses in CS_A mucilage seem related to semi-sterile system conditions. Higher viscosity of CS_B mucilage might reflect the need for enhanced water holding capacity of brace roots growing in drier conditions. A strong influence of environmental factors on mucilage properties even for a single genotype might play additional roles e.g. in the attraction of microbiomes. These aspects are relevant when assessing the role of mucilage in the rhizosphere, or when developing models of rhizosphere processes.