Using the non-invasively ion-selective microelectrode technique, flux profiles of K(+), Na(+) and H(+) in mature roots and apical regions, and the effects of Ca(2+) on ion fluxes were investigated in salt-tolerant poplar species, Populus euphratica Oliver and salt-sensitive Populus simonii x (P. pyramidalis + Salix matsudana) (Populus popularis 35-44, P. popularis). Compared to P. popularis, P. euphratica roots exhibited a greater capacity to retain K(+) after exposure to a salt shock (SS, 100 mM NaCl) and a long-term (LT) salinity (50 mM NaCl, 3 weeks). Salt shock-induced K(+) efflux in the two species was markedly restricted by K(+) channel blocker, tetraethylammonium chloride, but enhanced by sodium orthovanadate, the inhibitor of plasma membrane (PM) H(+)-ATPase, suggesting that the K(+) efflux is mediated by depolarization-activated (DA) channels, e.g., KORCs (outward rectifying K(+) channels) and NSCCs (non-selective cation channels). Populus euphratica roots were more effective to exclude Na(+) than P. popularis in an LT experiment, resulting from the Na(+)/H(+) antiport across the PM. Moreover, pharmacological evidence implies that the greater ability to control K(+)/Na(+) homeostasis in salinized P. euphratica roots is associated with the higher H(+)-pumping activity, which provides an electrochemical H(+) gradient for Na(+)/H(+) exchange and simultaneously decreases the NaCl-induced depolarization of PM, thus reducing Na(+) influx via NSCCs and K(+) efflux through DA-KORCs and DA-NSCCs. Ca(2+) application markedly limited salt-induced K(+) efflux but enhanced the apparent Na(+) efflux, thus enabling the two species, especially the salt-sensitive poplar, to retain K(+)/Na(+) homeostasis in roots exposed to prolonged NaCl treatment.

EXPLOR_STEP=$WICRI_ROOT/Bois/explor/PoplarV1/Data/Main/Exploration

HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 003692 | SxmlIndent | more

HfdSelect -h $EXPLOR_AREA/Data/Main/Exploration/biblio.hfd -nk 003692 | SxmlIndent | more

{{Explor lien
   |wiki=    Bois
   |area=    PoplarV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     pubmed:19638360
   |texte=   Calcium mediates root K+/Na+ homeostasis in poplar species differing in salt tolerance.
}}

HfdIndexSelect -h $EXPLOR_AREA/Data/Main/Exploration/RBID.i   -Sk "pubmed:19638360" \
       | HfdSelect -Kh $EXPLOR_AREA/Data/Main/Exploration/biblio.hfd   \
       | NlmPubMed2Wicri -a PoplarV1