Accumulation of membrane-bound polypeptides in roots of Al-sensitive and Al-resistant barley cultivars under Al, pH and metal stresses

Accumulation of five membrane-bound polypeptides in roots of Al-sensitive ( Alfor) and Al-resistant (Bavaria) barley cultivars were observed under stre ss conditions induced by different aluminium (Al3+) concentrations, pH valu es of root medium, and some heavy metal (Cu2+, Cd2+, Co2+) treatments. Alum inium in concentrations ranging from 1 up to 150 muM induced an increased a ccumulation of 24.5, 25.5, 25.0 and 26.5 kDa polypeptides in the Al-sensiti ve cultivar. These polypeptides accumulated already on the first day of Al treatment in Al-sensitive cultivar. The accumulation of these polypeptides was uniform without quantitative differences depending on Al dose. In Al-re sistant barley the accumulation of 25.5 and 26.5 kDa polypeptides appeared on the fourth day after application of 10 muM Al concentration while accumu lation of 24.5 and 25.0 kDa polypeptides were not detected either at 10 or 150 muM of Al. One polypeptide with molecular mass of 32 kDa was accumulate d in both barley cultivars. The accumulation started at 10 muM Al concentra tion on the fourth day of Al treatment without quantitative differences amo ng the applied Al concentrations. Changes in pH values of root medium (pH 3 .5-6.5) did not show any effect on the accumulation of the analysed polypep tides. However, differences were found between two barley cultivars during heavy metal treatment. Application of 10 muM concentration of heavy metals (Cu, Cd, and Co) in the root medium of Al-sensitive cultivar Alfor resulted in ac cumulation of polypeptides with molecular mass of 24.5, 25.5, 25.0 a nd 26.5 kDa very similar to Al treatment. On the other hand, the metal stre ss did not induce accumulation of these polypeptides in roots of the Al-res istant cultivar Bavaria.