Abstract
Abstract Using the method of compartmental analysis, the ion fluxes and compartment concentrations of Ca2+, K+ and Cl‐ have been compared in the untreated vegetative frond and the abscisic acid (ABA) induced turion of Spirodela polyrrhiza. The ABA‐induced turion is characterized by reduced Ca2+ exchange across the tonoplast and low vacuolar Ca2+ concentration relative to the vegetative frond. In addition the turion exhibits a higher plasmalemma flux with a correspondingly high Ca2+ concentration in the cytoplasm. The concentration of K+ and Cl‐ is much lower in the cytoplasm of the ABA‐induced turion than in the vegetative frond with the influx/efflux ratio at both the plasmalemma and the tonoplast being less than 1, a finding exhibited also in dormant storage tissue.Treatment of vegetative fronds with ABA for 18 h resulted in a reduced K+ plasmalemma efflux relative to untreated vegetative fronds and a concomitant increase in the cytoplasmic concentration. There was no rapid effect of ABA on Ca2+, K+ or Cl‐ fluxes through either membrane. These results are consistent with the notion that drastic changes in ion fluxes and concentrations in the turion are a secondary consequence of ABA‐induced development, possibly due to prior regulation by ABA of enzymes inherent to processes involved in membrane transport.
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