ISSN:
1573-5036
Keywords:
Al stress
;
Ca2+
;
H+ pump
;
K+ efflux
;
low pH
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract H+-ATPase activity of a plasma membrane-enriched fraction decreased after the treatment of barley (Hordeum vulgare) seedlings with Al for 5 days. A remarkably high level of Al was found in the membrane fraction of Al-treated roots. A long-term effect of Al was identified as the repression of the H+-ATPase of plasma membranes isolated from the roots of barley and wheat (Triticum aestivum) cultivars, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive). To monitor short-term effects of Al, the electrical membrane potentials across plasma membranes of both wheat cultivars were compared indirectly by measuring the efflux of K+ for 40 min under various conditions. The rate of efflux of K+ in Scout was twice that in Atlas at low pH values such as 4.2. Vanadate, an inhibitor of the H+-ATPase of the plasma membrane, increased the efflux of K+. Al repressed this efflux at low pH, probably through an effect on K+ channels, and repression was more pronounced in Scout. Al strongly repressed the efflux of K+ irrespective of the presence of vanadate. Ca2+ also had a repressive effect on the efflux of K+ at low pH. The effect of Ca2+, greater in Scout, might be related to the regulation of the net influx of H+, since the effect was negated by vanadate. The results suggest that extracellular low pH may cause an increase in the influx of H+, which in turn is counteracted by the efflux of K+ and H+. These results suggest that the ability to maintain the integrity of the plasma membrane and the ability to recover the electrical balance at the plasma membrane through a net influx of H+ and the efflux of K+ seem to participate in the mechanism of tolerance to Al stress under acidic conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00009573
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