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

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.

Notes

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