Effect of environmental conditions on physical properties of maize root mucilage.

Abstract

High viscosity, low surface tension and hydrophobicity are specific properties of maize root mucilage which contribute to modulate the spatial configuration of the liquid phase in soil pores. Being a hotspot for nutrient absorption, root exudation and microbial activity, the rhizosphere soil solution is suspected to chemically vary strongly upon time. Although the physical properties of maize root mucilage have been repeatedly measured in the last years, their variation upon a changing chemical environment and understanding of the chemical mechanisms governing these properties remain unexplored. Therefore, we investigated how flow and surface properties of maize root mucilage varied by changes in pH, CaCl2 and lecithin concentrations. Results reveal that the physical properties of mucilage can strongly vary depending on the environmental conditions. Low surface tension of maize root mucilage at pH7 was increased by addition of calcium. Upon pH change and lecithin addition, hydrophobic mucilage turned hydrophilic. Viscosity of mucilage decreased with increasing Ca concentration above 2.5 mM, the addition of 0.5 mg/L lecithin and a pH rise to 9. Such variations strongly suggest that the role of mucilage in hydraulic processes in the rhizosphere depends on changes of solutes concentration and composition, which themselves vary according to plant growth and soil water content. It seems that mucilage can best serve as a hydraulic bridge only under certain chemical environments, whose spatio-temporal occurrence in the changing rhizosphere remains to be defined.

Effect of changing chemical environment on physical properties of maize root mucilage

“…Post-hoc testing of pairwise comparisons for the boxplots was performed either by Tukey test in case Shapiro-Wilk normality test and Levene test were not significant (p > 0.05) or by a Games-Howell test. Raw data of all measurements are reported on Mendeley Data (Knott 2021).…”

“…K and Na were probably extracted in high amounts in the second and third EtOH precipitation, explaining the low recovery. Effect of purification on molecular size distribution Although the dextran calibration curve extended for molecular size between 1500 kDa (RT 16 min) and 80 kDa (RT 19 min) (Knott 2021), all mucilage peaks came either before or after the biggest or smallest dextran standard. Thus, their dextran equivalent molar mass is an estimation based on the calculated calibration curve.…”