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Sequential depolarization of root cortical and stelar cells induced by an acute salt shock – implications for Na + and K + transport into xylem vessels
Author(s) -
WEGNER LARS H.,
STEFANO GIOVANNI,
SHABALA LANA,
ROSSI MARIKA,
MANCUSO STEFANO,
SHABALA SERGEY
Publication year - 2011
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2011.02291.x
Subject(s) - xylem , depolarization , stele , biophysics , symplast , chemistry , botany , biology , biochemistry , cell wall , apoplast
Early events in NaCl‐induced root ion and water transport were investigated in maize ( Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 m m NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans‐root potential and a transient drop in xylem K + activity (A K+ ) within ∼1 min after stress onset. At this time, no detectable amounts of Na + were released into the xylem vessels. The observed drop in A K+ was unexpected, given the fact that application of the physiologically relevant concentrations of Na + to isolated stele has caused rapid plasma membrane depolarization and a subsequent K + efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl‐induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K + to the environment, this is associated with some K + shift from the stelar symplast to the cortex, resulting in K + being transiently removed from the xylem. Once Na + is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A K+ occurs.