Pre-Treatment of Bean Seedlings with Choline Compounds Increases the Resistance of Photosynthetic Apparatus to UV-B Radiation and Elevated Temperatures

Bean (Phaseolus vulgaris L. cv. Berbukskaya) seedlings were pre-treated with choline compounds, 19 mM 2-ethyltrimethylammonium chloride (Ch) or 1.6 mM 2-chloroethyltrimethylammonium chloride (CCh), during 24 h, then after 6 d the excised primary leaves were exposed to UV-B and high temperature stress. Chlorophyll (Chl) fluorescence, delayed light emission, accumulation of photosynthetic pigments, contents of thiobarbituric acid reactive substances, and activities of the active oxygen detoxifying enzymes (superoxide dismutase, ascorbate peroxidase, and glutathione reductase) were examined. Pre-treatment of plants with Ch or CCh enhanced the resistance of photosystem 2 (PS2) photochemistry to UV-B and heat injuries. The higher stress resistance can be explained by the increased activity of the detoxifying enzymes. The increased content of UV-B-absorbing pigments may also contribute to the enhanced resistance of choline-treated plants to UV-B radiation.     

Oxidative damage and antioxidant defense system in leaves of Vicia faba major L. cv. Bartom during soil flooding and subsequent drainage

The adaptive reactions of Vicia faba major L. cv. Bartom to 13-27 days soil flooding and to 14 days of drainage following 13-days of soil flooding were studied. Under flooding, oxygen diffusion rate (ODR) in the root zone decreased from 2.28–3.44 to 0.09–0.28?µmol O₂ m^?2 s^?1; the soil redox potential (Eh) decreased from 543 to 70 mV. Upon drainage of flooded soil the ODR and Eh values returned to the control levels. Oxidative damage and defense systems in leaves were assessed by the concentration of thiobarbituric acid reactive substances (TBARs) and by the activities of superoxide dismutase (SOD) and glutathione reductase (GR). Two stages of stress development are described. During the first stage (1–13 days) shoot dry mass did not decrease, the TBARs concentration and SOD activity increased, the GR activity decreased. The second stage (13–27 days) was characterized by a decrease in the TBARs concentration, SOD and GR activities, pigment concentrations and shoot dry mass. Drainage of flooded soil resulted in elevated concentrations of TBARs and also increased the activities of SOD and GR. Increased SOD activity in the first stage of hypoxic stress development and activations of SOD and GR at oxygen re-entry to soil are responsible for tolerance of Vicia faba to hypoxic and post hypoxic stress associated with soil flooding and subsequent drainage.     

Effects of silicon on growth processes and adaptive potential of barley plants under optimal soil watering and flooding

Barley (Hordeum vulgare L.) was grown in pots with brown loess soil and highly soluble amorphous silicon dioxide as the source of monosilicic acid to examine its influence on plant growth and adaptive potential under optimal soil watering and flooding. The adaptive potential of plants was estimated by the concentration of the thiobarbituric acid reactive substances (TBARs) as well as superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (AsP) activities. Application of amorphous silica to the soil increased the Si content in barley shoots and roots and stimulated their growth and biomass production under optimal soil watering. Soil flooding suppressed the growth both of the (−Si)- and (+Si)-plants. The intensity of oxidative destruction estimated by the concentration of TBARs was lower in the roots and leaves of the (+Si)-plants. Soil flooding induced SOD activity in the roots and in the leaves of the (−Si;+flooding) and (+Si;+flooding)-plants, but no significant differences were observed due to the Si treatment. GPX activity in the roots of (+Si)-plants was higher than in the (−Si)-ones under optimal soil watering, but under soil flooding no differences between (+Si)- and (−Si)-treatments were observed. AsP activity was not influenced by Si treatment neither under optimal soil watering nor under flooding. Thus, application of Si stimulates growth processes of barley shoots and roots under optimal soil watering and decreases intensity of oxidative destruction under soil flooding without significant changes in the activities of antioxidant enzymes.     

Principles of formation of the environment friendly program of management of arthropod pests and their enemies in an apple orchard agroecosystem in the North Caucasus

Ecological inefficiency of conventional IPM programs for apple orchard protection in the North Caucasus results from arbitrary use of compounds producing opposite ecological effects, i.e., broad-spectrum chemical insecticides after environment-friendly selective ones, which destroys the apple orchard agroecosystem. The investigation was aimed at developing an effective and ecologically acceptable program with alternation of environment-friendly compounds which act along the same vector to preserve the populations of natural enemies of the pests and thus to stabilize the apple orchard agroecosystem, i.e., create an ecological type of orchard. In this kind of orchards, broad-spectrum chemical pesticides are prohibited whereas selective biological compounds (including synthetic ones) and methods are welcomed. The test runs of the resulting pest and enemy management (PEM) programs based both on bioregulators (Insegar, Match, Dimilin) and bio-insecticides (Phytoverm™, Lepidocid™, etc.) in 2007 and 2009 demonstrated their high efficiency: the apple fruit damage by codling moth was 1.2% and 0.3%, respectively. The test of sticky bands fixed on apple tree trunks to prevent ants from getting to the crowns showed a significant increase in the abundance of predaceous bugs which sharply reduced the green apple aphid population.     

The effect of cadmium on CO<Subscript>2</Subscript> exchange,variable fluorescence of chlorophyll,and the level of antioxidant enzymes in pea leaves

CO₂ exchange, variable chlorophyll fluorescence, the intensity of lipid peroxidation (POL), and the activity of antioxidant enzymes in leaves of two-week-old pea seedlings (Pisum sativum L.) exposed to 0.01, 0.1, and 1 mM aqueous solutions of Cd(NO₃)₂ for 2 h were studied. Incubation with Cd²⁺ ions resulted in a reduction of the maximum quantum efficiency of photosynthesis, CO₂ uptake rate, and photosystem II (PSII) activity, as assessed by F _v/F ₀ ratio. The intensity of POL in leaves of all treated seedlings was below or close to the control level. The activity of superoxide dismutase (SOD) and glutathione reductase (GR) increased in all treatments; the activity of ascorbate peroxidase (AP) exceeded the control level only in seedlings exposed to the high Cd²⁺ concentration (1 mM), and the activity of peroxidase increased at the low concentration (0.01 mM). We found that the reduction in the activity of the photosynthetic apparatus under conditions of 2-h-long Cd²⁺-induced stress was not related to an intensification of POL processes. It was concluded that stimulation of the activity of antioxidant enzymes—SOD, GR, AP, and peroxidase—is a pathway for pea plant adaptation to toxic effect of cadmium.Translated from Fiziologiya Rastenii, Vol. 52, No. 1, 2005, pp. 21–26.Original Russian Text Copyright © 2005 by Balakhnina, Kosobryukhov, Ivanov, Kreslavskii.     

Effect of selenium on growth and antioxidant capacity of <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. during development of lead-induced oxidative stress

Effects of two selenium concentrations—0.4 and 0.8 mg Se⁶⁺ per kilogram of soil (treatments Se0.4 and Se0.8)—on seedling growth, chlorophyll content (Chl (a + b)), the content of thiobarbituric acidreactive substances (TBARs) indicative of peroxidation rates, and the activities of antioxidant enzymes (ascorbate peroxidase, AsP; glutathione reductase, GR; and guaiacol peroxidase, GPX) were studied in roots and leaves of wheat (Triticum aestivum L., cv. Triso) plants that were exposed for 14 days to oxidative stress induced by 50 and 100 mg Pb²⁺ per kilogram of soil (treatments Pb50 and Pb100, respectively). The pollution of soil with Pb²⁺ inhibited growth, lowered Chl (a + b) content, and intensified peroxidation. The content of TBARs increased by 44 and 72% in leaves and by 25 and 45% in roots for treatments Pb50 and Pb100, respectively. Activities of the antioxidant enzymes GR and GPX were higher in Pb²⁺-treated than in untreated (control) plants. The introduction of Se⁶⁺ into Pb²⁺-free soil (treatment Se0.4) was found to promote growth, stimulate AsP activity by 40% in leaves, and enhance AsP, GR, and GPX activities in roots by 38, 33, and 74%, respectively. The content of TBARs was reduced in Se⁶⁺-treated plants. By contrast, the treatment Se0.8 suppressed growth, elevated TBARs content, and stimulated activities of antioxidant enzymes in roots and leaves. The addition of 0.4 mg Se⁶⁺/kg to Pb²⁺-contaminated soil alleviated the negative influence of lead on plant growth, whereas the addition of 0.8 mg Se⁶⁺/kg aggravated the effect of Pb²⁺ contamination, especially in treatment (Pb100+Se0.8). Thus, the effectiveness of exogenous Se⁶⁺ application on growth and adaptive potential of plants cultivated under optimal pollutant-free conditions and on soils contaminated with lead depended on the concentration of Se⁶⁺ supplemented to soil and on the content of the stressor agent.     

Dihydroquercetin protects barley seeds against mold and increases seedling adaptive potential under soil flooding

Barley (Hordeum vulgare L.) seeds were soaked in aqueous 10⁻⁴ M dihydroquercetin (DHQ) to examine its influence on seed germination and further growth of seedlings under optimal soil watering and flooding conditions. The adaptive potential of the plants was estimated by the content of thiobarbituric acid reactive substances (TBARs) and the activity of ascorbate peroxidase (AsP). High-grade seeds were germinated evenly under (−DHQ)- and (+DHQ)-treatments. Low-grade seeds soaked in DHQ, showed no mold and twofold germination rate in comparison with the same seeds soaked in water. The seedlings grown from the similarly germinated seeds did not differ from each other in the shoot growth, independent of the DHQ-pretreatment. The root growth was higher in DHQ-pretreated plants. Soil flooding suppressed the shoot and root growth rates in non-pretreated and DHQ-pretreated plants, however TBARs content was lower in the roots and leaves of (+DHQ)-seedlings as compared to the (−DHQ)-ones. The activity of AsP increased more significantly in the (+DHQ)-plants. The ratio between TBARs content and the AsP activity was lower in the leaves of (+DHQ)-plants both under optimal soil conditions and flooding. Thus, the treatment of low-grade barley seeds with DHQ protects the seeds against mold and increases adaptive potential of the seedlings.     

Structural organization of chloroplast of tomato plants <Emphasis Type="Italic">Solanum lycopersicum</Emphasis> transformed by Fe-containing superoxide dismutase

In this work we analyzed the results of the transformation of tomato plants Solanum lycopersicum by gene FeSOD1 from Arabidopsis thaliana, equipped with the signal sequence for targeting into chloroplasts. PCR analysis showed that the gene was integrated into the genome of several tomato plants that underwent transformation followed by selection in the kanamycin-containing medium. Two lines, provisionally denoted as nos. 6 and 8, were selected from the independent transformants. Line 6 was characterized by a reduced growth rate and altered leaves and line 8, by normal growth and leaves typical for control plants. Both lines showed a significant increase in SOD activity. In line 8 the increase in SOD activity was accompanied by an increase of ascorbate peroxidase activity, and in line 6 this effect was not present. Electron microscopic analysis of parenchymal and guard cells of both lines was performed, with an emphasis on the ultrastructural organization of chloroplasts. It is shown that the chloroplasts of the two transgenic lines differ in the number and size of starch grains and deposited plastoglobules as well as in the organization of lamellae and grana. Taken together, the results indicate that the expression of the introduced gene FeSOD1 has a significant effect on metabolic processes in the plastids. The findings are discussed in relation to the hypothesis about the importance of low concentrations of ROS for the integration of structure and function of chloroplasts.