The dynamics of oxygen concentration, pH value, and organic acids in the rhizosphere of Juncus spp.

► We used planar optodes for simultaneous analysis of rhizosphere pH and O2 dynamics. ► Pronounced diurnal changes of O2 concentration and pH along the roots were measured. ► Records of 8 weeks revealed a dynamic range of 0-200 μmol O2 L−1 and ±1.4 pH units. ► Organic acid content decreased up to 58% within 4 mm from the bulk soil to the root.