Search

This work focuses on the investigation of forage crops hybrid fescue and legume alfalfa response to drought at different levels of nitrogen fertilization. Plants were grown in pots filled with a mixture of field soil, perlite and fine sand with three (N0, N60 and N90 kg/ha) levels of nitrogen fertilization in a greenhouse. Drought stress was applied by withholding watering for 1 week, after which plants were left for a recovery period of 1 week. In most cases, the morphological indices of alfalfa did not differ significantly between the treatments. In contrast, the above-ground biomass of fescue grown under well-watered conditions was largely enhanced by N addition. The main trend of JIP test parameters was that nitrogen fertilizer did not have a significant effect on alfalfa. Contrarily, additional nitrogen content increased energy fluxes (such as absorption, trapping, electron transport, reduction of end acceptors) and density of reaction centres not only in well-watered but also in drought-affected fescue plants. An increase in nitrogen fertilizers increased content of pigments and flavonoids in fescue leaves. In conclusion, the stress tolerance index of hybrid fescue increased along with the increase in N content due to more efficient use of light energy and increased antioxidative capacity, all of which led to significantly higher production of above-ground biomass at higher N levels and drought stress. [ABSTRACT FROM AUTHOR]

Intensity and frequency of heat waves (HW) accompanied by drought are increasing, however, still little is known about its effect on forage plants. A pot experiment was carried out in growth chambers in order to elucidate the multiple response of forage rape to combined HW and drought (HD) under current and elevated CO2 (HD + CO2). Forage rape was proved to be relatively HD‐resistant plant, with no significant and long‐term effects on shoot growth and photosynthetic performance, and effective stimulation of antioxidative system, especially in the case of HD + CO2 exposure. Activities of enzymes of ascorbate–glutathione cycle were further stimulated by elevated CO2 even after the termination of HD treatment. Nutritive value of forage rape was also positively affected, as was shown by elevated content of water‐soluble carbohydrates after exposure and starch after the period of recovery (up to 80% and 92%, respectively). Concentrations of most macro‐ and microelements were increased, and stabilized higher or equalized to control level after the period of recovery in a similar pattern for HD and HD + CO2 exposure. However, content of Ca was reduced and remained significantly lower (~20%). One of the most important negative and lagged HD effects was reduction of dry root biomass (~30%), most possibly induced by accumulation of non‐structural carbohydrates in shoot and was not mitigated by elevated CO2. To conclude, forage rape was proved to be a promising forage crop for the future climate with increased frequency of HWs; however, a special attention should be paid to the lagged effects, such as inhibition of root growth. [ABSTRACT FROM AUTHOR]

Different species have different sensitivity to heat waves; therefore, interspecific competition may affect the crop response to heat waves. We investigated the effects of heat waves on spring barley (Hordeum vulgare L.) grown with and without wild mustard (Sinapis arvensis L.) as well as the recovery of barleys from stress. The plants were exposed to a 7‐day 35/28ºC (day/night) heat wave at ambient CO2 (400 μmol/mol) and elevated CO2 (800 μmol/mol). All seedlings were rehydrated and returned to control conditions (21/14ºC, CO2 400 μmol/mol) after the cease of heat wave and grown for a 7‐day period of recovery. Heat wave had more pronounced negative effect on the barley's aboveground biomass under competition with mustard, whereas the response of root biomass was not influenced by the presence of weeds. The heat wave induced reductions in barley's photosynthetic rate, stomatal conductance and water use efficiency under interspecific competition were higher compared to monocultured conditions. Interspecific competition impaired and delayed the recovery of barley's biomass production and leaf gas exchange parameters after heat wave. Elevated CO2 slightly mitigated negative heat wave impact on the growth and leaf gas exchange parameters but had no effect during the recovery period. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the possibilities and the mechanisms of spring barley (Hordeum vulgareL.) 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. [ABSTRACT FROM AUTHOR]

Aims oxidative stress is one of the most important mechanisms in a plant's reaction to the effects of different stressors; however, its role in plants' resistance is still poorly understood. The objective of this study is to evaluate an influence of oxidative stress induced by stress factors of different origin--ozone, ultraviolet (uV)-b radiation, drought, cadmium (Cd) and copper (Cu), to growth of spring barley and to check the hypothesis, that intensification of oxidative stress is the main factor of growth depression induced by strong treatments of different stressors; meanwhile, mitigation of oxidative stress determines eustress-induced growth stimulation. Methods a pot experiment was carried out in phytotron chambers with a controlled environment. spring barley (Hordeum vulgare l.) plants were exposed to different doses of investigated environmental stress factors (O3, uV-b radiation, drought, Cd and Cu), and their effects on shoots growth, accumulation of superoxide (O2·-), intensification of lipid peroxidation and antioxidative protection (superoxide dismutase, glutathione reductase and catalase activities and concentration of carotenoids) were measured. analysis of variance (aNoVa) with classical eta-squared (η²) values was used to evaluate and to compare the contribution of non-specific oxidative stress and stressor-specific mechanisms on plants growth. Important Findings low doses of most stressors stimulated antioxidative protection and growth of barley shoots, reduced the concentration of O2·- and/or intensity of lipid peroxidation. Whereas an impairment of growth and intensification of oxidative stress as well as a reduction in concentration of carotenoids and further increase in activity of antioxidative enzymes were noticed when the intensity of the stressors was increased. In the cases of ozone and uV-b stress, the effects of oxidative stress on plant growth was mitigated by strong antioxidative protection--highly increased catalase (CaT) and superoxide dismutase (soD) activities, respectively. In the cases of drought and Cu, relatively strong oxidative stress was the major cause of plant growth depression. additionally, mitigation of oxidative stress due to increased soD activity was likely to be one of the main causes of growth stimulation induced by low doses of uV-b, Cd and Cu stress. Possible reasons for O3-induced growth stimulation were increased CaT activity and concentration of carotenoids. generalizing the effects of different stressors, the contribution of non-specific oxidative stress on plant growth was stronger compared with stressor-specific action mechanisms: oxidative stress determined 42% of the changes in plants' dry biomass, whereas the contribution of stressor-specific mechanisms accounted for 35% of variability in barley growth. [ABSTRACT FROM AUTHOR]

Oxidative stress is accepted to play a significant role in stress symptoms, caused by different stressors in a variety of organisms. In this study seedlings of spring barley ( Hordeum vulgare L.) were exposed to a wide range of copper, zinc, chromium, nickel, lead and cadmium concentrations in order to determine the relationships between heavy metals-induced oxidative stress and plant growth inhibition. All investigated heavy metals induced an essential increase in lipid peroxidation and a reduction of dry biomass along with an increase in metal concentration in the nutrient solution. A very close and statistically significant exponential relationship between lipid peroxidation and growth inhibition was detected in this study. According to the results of analysis of variance (ANOVA), the intensity of nonspecific oxidative stress is identified as the main factor of barley growth inhibition, explaining 75% of total variance. Almost 10% of growth inhibition is attributed to the specific impact of heavy metals. The most pronounced increase of malondialdehyde content and growth inhibition was observed in Cu and Cd treatments, whereas the lowest changes in observed indicators were detected after exposure to Zn and Pb. [ABSTRACT FROM AUTHOR]

Intensity and frequency of heat waves (HW) accompanied by drought are increasing, however, still little is known about its effect on forage plants. A pot experiment was carried out in growth chambers in order to elucidate the multiple response of forage rape to combined HW and drought (HD) under current and elevated CO2 (HD + CO2). Forage rape was proved to be relatively HD‐resistant plant, with no significant and long‐term effects on shoot growth and photosynthetic performance, and effective stimulation of antioxidative system, especially in the case of HD + CO2 exposure. Activities of enzymes of ascorbate–glutathione cycle were further stimulated by elevated CO2 even after the termination of HD treatment. Nutritive value of forage rape was also positively affected, as was shown by elevated content of water‐soluble carbohydrates after exposure and starch after the period of recovery (up to 80% and 92%, respectively). Concentrations of most macro‐ and microelements were increased, and stabilized higher or equalized to control level after the period of recovery in a similar pattern for HD and HD + CO2 exposure. However, content of Ca was reduced and remained significantly lower (~20%). One of the most important negative and lagged HD effects was reduction of dry root biomass (~30%), most possibly induced by accumulation of non‐structural carbohydrates in shoot and was not mitigated by elevated CO2. To conclude, forage rape was proved to be a promising forage crop for the future climate with increased frequency of HWs; however, a special attention should be paid to the lagged effects, such as inhibition of root growth. [ABSTRACT FROM AUTHOR]