Abstract: | This paper deals with the responses of roots of wheat {Triticumaestivum L.) to hypoxia with special emphasis on the effectsof severe O2 deficiency on membrane integrity, loss of K+ fromthe root and root membrane potentials. Seminal and crown roots of 26-d-old plants exposed to severehypoxia (0.003 mol O2 m3) for 3 h or 10 d prior to excisionand subsequently exposed to hypoxic solutions, had slightlylower rates of sorbitol influx and a slightly smaller apparentfree space than roots in aerated solutions. These results indicatethat neither a few hours nor a 10-d exposure to hypoxia hadadverse effects on the membrane integrity of the bulk of thecells in the roots. However, both 6-d-old seedlings and 26-d-oldplants lost K+ from the roots following their transfer fromaerated to hypoxic nutrient solutions. In the 26-d-old plants,which were of high nutritional status, there was a net K+ effluxfrom the roots to the external solution. In contrast, with the6-d-old seedlings, which were of low nutritional status, thedecrease in the K+ content of the roots was smaller than thenet K+ uptake to the shoots. Exposure of excised roots to 0.008 mol O2 m3caused arapid and reversible membrane depolarization from 120to 80 mV. These data and the magnitude of thenet effluxes strongly suggest that K+ losses during the earlystages of hypoxia are due to membrane depolarization ratherthan to increases in the permeability of membranes to K +. Key words: Hypoxia, membrane integrity, membrane potentials, seminal and crown roots |