INHIBITION OF ION UPTAKE AND GROWTH OF WHEAT AND RICE EXPOSED TO NITRITE AT LOW PH

The effects of NO2- on the ion uptake and growth of wheat (Triticum ae stivum L. cv. GK Othalom) and rice (Oryza sativa L. cv. Oryzella) seed lings were studied in hydroponic cultures at different pH values. Incr easing concentrations of NaNO2 decreased the K+, H2PO4-, SO42- and NO3 - uptake of the roots. The inhibitory effect of 1 mM NO2- on ion uptak e and growth was small or negligible between pH 6-7, but increasingly severe at lower pH. The inhibitory effect of NO2- differed considerabl y for nutrients and was also different for species. Rice seedlings wer e more sensitive than wheat seedlings to NO2- treatment. The parallel efflux studies revealed no significant effect of even high concentrati on of NaNO2 (10 mM) on the K+ efflux of the roots at pH 6.5, but stron gly enhanced the K+ efflux of the roots at pH 4 already at 1 mM NaNO2. The results indicate that NO2- may initiate membrane damage at low pH . The presence of NO3- in the uptake and/or growth solution decreased the inhibitory effect of NO2-.