Improvement of tolerance to paraquat and drought in barley (Hordeum vulgare L.) by exogenous 2-aminoethanol: effects on superoxide dismutase activity and chloroplast ultrastructure

In pot and field experiments conducted over several years, the influence of 2-aminoethanol on growth and yield of barley (Hordeum vulgare L.) under conditions of different water supply was studied. Under drought stress, 2-aminoethanol pre-treatment increased the grain yield of barley by 5-30%. The effects of application of the plant constituent, 2-aminoethanol on biomass formation, the content of chlorophyll and protein and the activities of superoxide dismutases (SOD) were studied in drought stressed barley plants. When plants were treated with 2-aminoethanol, and were exposed to water deficit, growth inhibition and chlorophyll content losses diminished. Analyses of SOD activity by native PAGE indicated the presence of two Cu/Zn-SOD isoenzymes in barley shoots. The activity of Cu/Zn-SOD II, the major isoenzyme in barley shoots, was strongly stimulated by 2-aminoethanol. Drought stress also induced a strong increase in the activity of Cu/Zn-SOD II, but the combined effect of 2-aminoethanol application and drought resulted in the highest Cu/Zn-SOD II activity. We studied further the protective effects of 2-aminoethanol treatment on chloroplast ultrastructure by electron microscopy. Here, paraquat was used as a causal agent of oxidative stress. At sublethal paraquat doses (0.1-1 mM), 2-aminoethanol could prevent the membrane deterioration. The results indicate a role of 2-aminoethanol pre-treatment in the protection against oxidative stress in plants.