Oxygen deficiency and salinity affect cell‐specific ion concentrations in adventitious roots of barley ( H ordeum vulgare )

Summary Oxygen deficiency associated with soil waterlogging adversely impacts root respiration and nutrient acquisition. We investigated the effects of O 2 deficiency and salinity (100 mM NaCl) on radial O 2 concentrations and cell‐specific ion distributions in adventitious roots of barley ( Hordeum vulgare ). Microelectrode profiling measured O 2 concentrations across roots in aerated, aerated saline, stagnant or stagnant saline media. X‐ray microanalysis at two positions behind the apex determined the cell‐specific elemental concentrations of potassium (K), sodium (Na) and chloride (Cl) across roots. Severe O 2 deficiency occurred in the stele and apical regions of roots in stagnant solutions. O 2 deficiency in the stele reduced the concentrations of K, Na and Cl in the pericycle and xylem parenchyma cells at the subapical region. Near the root apex, Na declined across the cortex in roots from the aerated saline solution but was relatively high in all cell types in roots from the stagnant saline solution. Oxygen deficiency has a substantial impact on cellular ion concentrations in roots. Both pericycle and xylem parenchyma cells are involved in energy‐dependent K loading into the xylem and in controlling radial Na and Cl transport. At root tips, accumulation of Na in the outer cell layers likely contributed to reduction of Na in inner cells of the tips.