Potassium transport in wheat seedlings grown with different potassium supplies.

The K+(86Rb) uptake into the roots and the translocation to the shoots of 11‐day‐old intact wheat seedlings (Triticum aestivum L. cv. Martonvásári 8) were investigated using plants grown with different K+ supplies. The effects of environmental conditions (darkness, humidity) and of metabolic and transport inhibitors (oligomycin, disalicylidene‐propanediamine, 2,4‐dinitriphenol, diethylstilbestrol, colchicine) were also studied. Plants with K content of about 0.2 mmol/g dry weight in the root and 0.5 mmol/g dry weight in the shoot (low K status) showed high K+ uptake into the roots and high translocation rates to the shoots. Both transport processes were very low in plants with K content of more than 1.5 and 2.2 mmol/g dry weight in the root and shoot, respectively (high K status). Darkness and a relative humidity of the air of 100% did not influence K+ uptake by roots, but did inhibit upward translocation and water transport. Inhibition of photosynthesis and treatments with diethylstilbestrol (10−5 mol/dm3), as well as with colchicine resulted in inhibition of translocation in plants of low K status, but these inhibitors had little effect on K+ uptake by the roots. Oligomycin, 2,4‐dinitrophenol and diethylstilbestrol (10−4 mol/dm3), however, inhibited K+ uptake by the roots. In general, K+ transport processes were almost unchanged in plants of high K status. It is concluded that only plants of low K status operating with active K+ transport mechanisms are responsive to environmental factors. In high K+ plants the transport processes are passive and are uncoupled from the metabolic energy flow.