An effect of Na+ on K+ uptake in intact seedlings of Zea mays

Models for the regulation of K⁺ uptake in higher plant roots have become more complex as studies have moved from the level of excised low-salt roots to that of intact plants grown under fully autotrophic conditions. In this paper we suggest that some of the differences between the conditions are qualitative, possibly requiring fundamental changes to the model, rather than simply quantitative.
The uptake of K⁺ by low-salt roots of Zea mays L. (A619 x Oh 43) x A632], was independent of Na⁺ concentration over a wide range. However, independence of Na⁺ was not the case in plants grown on complete nutrient medium in the light: inclusion of Na⁺ in the uptake medium enhanced K⁺ uptake. In the presence of Na⁺, K⁺ uptake rates were similar in whole plants with high root K⁺ contents to rates in excised or intact, low-salt roots.