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1991 (1)
1985 (1)
1Author    M. Baier, W. HartungRequires cookie*
 Title    Cytoplasmic pH and Abscisic Acid Transport across Guard Cell Membranes  
 Abstract    The cytoplasmic pH value o f guard cells o f Valerianella locusta was determined from the distribution o f the weak acid [l4C]ABA between the medium and the cell, which was shown to be 8.1 ± 0.1. Treatment o f guard cells in media with low pH (pH 5.0) and different concentra­ tions o f sodium acetate (0 -5 m o lm '3) caused a considerable acidification o f the cytoplasm (6 .6 -7 .7). Using the compartmental analysis we determined also the fluxes o f ABA at the plas­ ma membrane o f guard cells (<I>co) and at the tonoplast o f guard cells (<t>cv) under steady state conditions. The flux o f ABA from the cytoplasm into the vacuoles (tonoplast flux) was de­ pendent upon the cytoplasmic pH. The data give evidence that A B A " is transported across the tonoplast by a saturable transport com ponent. The A BA flux at the plasma membrane seemed to be independent o f the cytoplasmic pH. 
  Reference    Z. Naturforsch. 46c, 106—110 (1991); received September 24 1990 
  Published    1991 
  Keywords    ABA Transport, Cytoplasmic pH, Guard Cells, Plasmamembrane, Tonoplast 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0106.pdf 
 Identifier    ZNC-1991-46c-0106 
 Volume    46 
2Author    Friedrich, C. Hristian, B. Aum AnnRequires cookie*
 Title    A Patch Clamp Study of Tonoplast Electrical Properties in Vacuoles Isolated from Chenopodium rubrum Suspension Cells  
 Abstract    -W ilhelm B en tru p , B ernd H offm ann , M aria G o g arten -B o ek els, Jo h a n n P ete r G ogarten The patch clamp technique has been applied to isolated vacuoles from green suspension cells of Chenopodium rubrum to record electrical parameters of the tonoplast. In a symmetrical K* solution of 46 mM, the membrane displays a near zero voltage, whereas 2 mM ATP will hyper-polarize it to 15 or 20 mV (vacuole positive). The conductance amounts to about one S-m~2. Fluctuations of the clamp current are explained by an unknown channel species having opening times of 5 — 10 ms. Together with previous work on a tonoplast vesicle preparation and unpub­ lished data on vacuoles from our laboratory, the present results indicate an electrogenic mem­ brane ATPase pumping protons from the cytoplasm to the vacuole. 
  Reference    Z. Naturforsch. 40c, 886 (1985); received October 23 1985 
  Published    1985 
  Keywords    Patch Clamp, Membrane ATPase, Tonoplast, Vacuole, Chenopodium rubrum L 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0886.pdf 
 Identifier    ZNC-1985-40c-0886 
 Volume    40