Irena Januškaitienė

Changes in the sensitivity of agricultural plants to the impact of ozone and UV-B radiation in simulated warmer climate conditions@@@Kultūrinių augalų jautrumo ozonui, UV-B spinduliuotei ir dirbtinai sukurto šiltesnio klimato sąlygoms pokyčiai

The sensitivity of agricultural crops and weed to the impact of ozone and UV-B radiation was evaluated according to changes in their dry biomass and concentration of photosynthetic pigments. Pisum sativum L., Raphanus sativus L. and Phleum pretense L. were most sensitive to the impact of ozone in current climatic conditions (350 ppm of CO2 and 21 °C day/14 °C night temperatures). The sensitivity of all test crops to the impact of ozone decreased significantly under warmer cli matic conditions – 700 ppm of CO2 and 25 °C day/19 °C night temperatures. Pisum sativum L. and Chenopodium album L. appeared to be most sensitive to the impact of UV-B radiation under current climatic conditions. Changes in the sensitivity of plants to the impact of UV-B radiation under warmer climatic conditions were not as pronounced as those for ozone, and were highly species-dependent. Sensitivity to the impact of UV-B radiation under warmer climatic conditions decreased for Lycopersicon esculentum Mill. and Chenopodium album L. and increased for Raphanus sativus L. and Phleum pretense L.

The role of oxidative stress in spring barley cross-adaptation to different heavy metals

ABSTRACT The aim of this study is to investigate the possibilities and the mechanisms of spring barley (Hordeum vulgare L.) cross-adaptation to different heavy metals after hardening with ozone (O3), drought and UV-B radiation. Dry shoot biomass, accumulation of superoxide (O2˙−) and malondialdehyde (MDA), and activities of enzymes superoxide dismutase (SOD), glutathione reductase (GR) and catalase (CAT) were measured after hardening and heavy metal treatments. Seedlings, exposed to ozone and drought prior to copper (Cu) treatment, showed significantly increased tolerance to this heavy metal. The most possible causes of cross-adaptation to this redox-active heavy metal, which triggered very strong oxidative stress in nonhardened barley seedlings, were increased CAT activity, mitigation of O2˙− accumulation and lipid peroxidation. Cross-adaptation to cadmium (Cd) was induced only by drought hardening. In this case, however, adaptation had lower effect on antioxidative enzymes, did not altered O2˙− accumulation and even slightly increased the intensity of lipid peroxidation. The study reveals that stimulation of CAT activity and mitigation of oxidative stress are the main reasons for plant adaptation to Cu; whereas cross-adaptation to Cd, heavy metal with much lower oxidative capacity, is determined by the mechanisms that are not related to oxidative stress directly.