Effects of aluminium on growth and kinetics of K⁺(⁸⁶Rb) uptake in two cultivars of wheat (Triticum aestivum) with different sensitivity to aluminium

Two cultivars of wheat (Triticum aestivum L. cvs Kadett and WW 20299) were grown for 9 days with 20% relative increase in nutrient supply per day at pH 4.1. Aluminium at 50 μ M retarded the growth of roots more than that of shoots in both cultivars, thus decreasing the root/shoot ratio. The inhibition was largest in WW 20299. With long term Al treatment (9 days), K m for K + ( 86 Rb) influx increased five times in both cultivars and V max decreased in WW 20299. Efflux of K + ( 86 Rb) was little affected. When the roots were treated with aluminium for two days, only relative growth rate of roots was retarded, while growth of shoots was unaffected and influx of K + ( 86 Rb) adjusted to the actual K + demand of the plants. It is concluded that the effects of aluminium on K + uptake in these wheat cultivars are not primary factors contributing to aluminium sensitivity. However, in soil with Al the demand for a comparatively high concentration of K + to maintain an adequate K + uptake rate, in combination with a slow growth rate of the roots, may secondarily lead to K + deficiency in the plants.