Abstract
Segments of oat (Avena sativa L.) roots which had been exposed to 1 millimolar CdSO4 in quarter-strength Hoagland No. 1 solution exhibited decreased respiratory rates, ATP levels, membrane-bound ATPase activity, and reduced K+ fluxes. Respiration and ATP levels were decreased after a 2-hour treatment with 1 millimolar CdSO4 to 65 and 75%, respectively, of control rates. A membrane-bound, Mg2+-dependent, K+-stimulated acid ATPase was rapidly inhibited to 12% of control activity in the presence of 1 millimolar CdSO4. Potassium uptake into root segments was inhibited to 80% of control values after 30 minutes in the presence of CdSO4. A 2-hour pretreatment of root segments with CdSO4 inhibited K+ uptake to 15% of control values. Cytoplasmic K+ efflux was inhibited with 1 millimolar CdSO4.
The rates and the degree of Cd2+ inhibition of the parameters listed above suggest that one of the first sites of Cd2+ action is the plasmalemma K+ carrier (ATPase) in oat roots.
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