The effects of salinity on ion concentrations within the root cells of Zea mays L.

Zea mays is a salt-sensitive crop species which in saline (≦100 mol m-3 NaCl) conditions suffers considerable growth reduction correlated with elevated Na+ and Cl- concentration within the leaves. To increase understanding of the regulation of ion uptake and transport by the roots in saline conditions, ion concentrations within individual root cortical cells were determined by X-ray microanalysis. There was variation in Na+, K+ and Cl- distributions among individual cells, which could not be correlated with their spatial position in the roots. Generally, however, in response to saline growth conditions (100 mol m3 NaCl) Na+ and Cl- were mostly localized in the vacuoles, although their concentrations were also sometimes increased in the cytoplasm and cell walls. The concentration of K+ in the cytoplasm was usually maintained at a level (mean 79 mol m-3) compatible with the biochemical functions ascribed to this ion.