Potassium uptake by Marianna plum under limited oxygen and elevated carbon dioxide levels in the root atmosphere

Abstract

Abstract Potassium (K) uptake rates were determined for Marianna 2624 rootstocks with ‘French’ prune scions using the nutrient solution depletion technique. The nutrient solutions were bubbled with factorial combinations of nitrogen (N2), oxygen (O2), and carbon dioxide (CO2) to create treatment root atmospheres with O2 ranging from 0.01 to 0.10 m3/m3 and CO2 ranging from 0 to 0.05 m3/m3. The K+ uptake rate was more susceptible to O2 deprivation than to elevated CO2 in the root atmosphere. Decreasing O2 levels from 0.10 m3/m3 decreased K+ uptake in a hyperbolic fashion to no net uptake at 0.01 m3/m3 O2. Increasing root atmosphere CO2 from 0 to 0.05 m3/m3 had a small depressing effect on net K+ influx from 60 μM K+ solutions at 0.10 and 0.05 m3/m3 O2, but no effect when O2 was 0.025 or 0.01 m3/m3. Elevating CO2 decreased Km for the net K+ influx rate at 0.10 and 0.05 m3/m3 O2. Increased pH buffering from higher HCO3 concentration at the plasma membrane surface was suggested to explain the CO2 effect on Km.