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Sunflower plants (Helianthus annuus L.) cv. 1114 were used as test plants to investigate the combined toxicity effect of heavy metals present in soils collected from three different locations of a polluted area near a non-ferrous metal smelter. Soils were designated as highly contaminated, moderately contaminated and non-contaminated (control) based on the content analysis of soil samples. The photosynthetic performance was assessed by the changes in the functional activity of PS1 (photosystem 1) and PS2 (photosystem 2). Evidence for accelerated electron flow beyond the first qiunone acceptors in PS2 (QA) but not related with accelerated reduction of the first acceptor of light in PS1 (P700) is presented. The retarded rate of the slower (IDP) increase of the rapid phase of Kautsky effect (OIDP) as well as the lower level of QB-nonreducing PS2 reaction centers in HCS plants suggested an accelerated rate of electron flow in the PS2 acceptor side. The response of the antioxidant defense system included enhancement of superoxide dismutase (SOD) activity, total antioxidant activity and content of flavonoids. Changes in thylakoid electron transport chain reactions accompanied with altered oxidative stress-related metabolic activity could be considered as a protective mechanism operating in conditions of combined heavy metal toxicity. [ABSTRACT FROM AUTHOR]

Tropospheric ozone (3) is one of the most widespread atmospheric pollutants in many parts of the world. Elevated ambient O3 concentrations have deleterious effects on the physiological status and productivity of a wide range of plant species. Experiments with controlled O3 fumigation are often performed in order to distinguish O3-induced injury from a wide range of injury symptoms caused by other environmental stress agents. In the present study, branches of common beech (Fagus sylvatica L.) were subjected to O3 fumigation for three days under controlled conditions. Ozone was provided at a concentration of 600 ppb in the course of 6 h during the day. The visible foliar symptoms of injury appeared as small pale green dots on the adaxial leaf surface. By the end of the first day, these dots were spread on the entire leaf surface. The acute O3-induced symptoms developed rapidly as reddish-brown stipple which enlarged covering the entire leaf surface on the third day of O3 exposure. These typical visible symptoms could serve as indicators of the presence of phytotoxic levels of O3 in natural conditions. Ozone fumigation treatment caused a significant decrease in the amount of total chlorophyll as well as metabolic changes in the antioxidant defense system of beech leaves. Elevated total antioxidant and free radical scavenging activities indicated enhanced capacity of the non-enzymatic plant defense system in response to oxidative stress caused by O3-induced generation of reactive oxygen species (ROS). Total flavonoid and anthocyanin contents were also increased. The enhanced activities of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (PO) can serve as indicators of oxidative burst caused by O3 fumigation in beech leaves. [ABSTRACT FROM AUTHOR]

Plants are susceptible to heavy metal toxicity and in order to avoid its detrimental effects they respond in a variety of ways. The toxic effect depends on the type of metal, ion concentration, plant species, and stage of plant growth. The present review describes recent advances in understanding the genetic and molecular basis of heavy metal tolerance in plants with special reference to heavy metal accumulating plants. The specifics of Pb tolerance, uptake and accumulation in plants are described. The phytoextraction of Pb by Helianthus annuus and other accumulating species is compared. Some approaches to improve the phytoextraction capability of sunflower plants are discussed. [ABSTRACT FROM AUTHOR]

In the present study, the effect of excess Zn and Pb ions added to the nutrient solution of hydroponically grown sunflower plants was studied in order to evaluate their impact on the properties of leaf tissue by employing an electrolyte leakage kinetics model. Based on the behavior of model parameters, it was demonstrated that treatment with excess Zn had a stronger effect on leaf leakage kinetics than Pb. This could be attributed to the higher mobility of Zn ions which were more readily transported towards the leaves in comparison to Pb. Ion fluxes through different subcellular compartments, namely apoplast (including cell wall) and symplast (comprising the vacuole and cell membranes) were used to explain the changes in ion leakage kinetics as reflecting the functional status of cellular membranes. [ABSTRACT FROM AUTHOR]

The effect of high temperature (HT) and dehydration on the activity of photosynthetic apparatus and its ability to restore membrane properties, oxygen evolution, and energy distribution upon rehydration were investigated in a resurrection plant, Haberlea rhodopensis. Plants growing under low irradiance in their natural habitat were desiccated to air-dry state at a similar light intensity [about 30 μol(photon) m −2 s −1] under optimal day/night (23/20°C) or high (38/30°C) temperature. Our results showed that HT alone reduced the photosynthetic activity and desiccation of plants at 38°C and it had more detrimental effect compared with desiccation at 23°C. The study on isolated thylakoids demonstrated increased distribution of excitation energy to PSI as a result of the HT treatment, which was enhanced upon the desiccation. It could be related to partial destacking of thylakoid membranes, which was confirmed by electron microscopy data. In addition, the surface charge density of thylakoid membranes isolated from plants desiccated at 38°C was higher in comparison with those at 23°C, which was in agreement with the decreased membrane stacking. Dehydration led to a decrease of amplitudes of oxygen yields and to a loss of the oscillation pattern. Following rehydration, the recovery of CO 2 assimilation and fluorescence properties were better when desiccation was performed at optimal temperature compared to high temperature. Rehydration resulted in partial recovery of the amplitudes of flash oxygen yields as well as of population of S 0 state in plants desiccated at 23°C. However, it was not observed in plants dehydrated at 38°C. [ABSTRACT FROM AUTHOR]

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Copyright of Stratum Plus Journal is the property of P.P. Stratum plus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

EU's Biodiversity Strategy to 2020 sets a 15% restoration target. However, the understanding of restoration as a management tool remains ambiguous at EU and Member State levels. As a country with rich biodiversity but low GDP, a well-defined priority setting approach is key for Bulgaria. The "Methodological framework for assessment and mapping of ecosystem condition and ecosystem services in Bulgaria" proposes a transition towards ecosystem management and monitoring of the Socio-Ecological System (SES), to be embedded in the environmental policy framework. We extend the analogy between SES and the human body's system in the Traditional Chinese Medicine (TCM) as a way to inform restoration priority setting and development of restoration and monitoring tools at several levels: We apply the analogy and find that spatially explicit decision making on restoration, streamlined ecosystem monitoring and a number of other issues (green infrastructure, designation of protected areas, defragmentation and connectivity, cumulative impact assessment, etc.), are easier to understand, communicate, account for and manage. Ecosystem restoration is priority for China and the country has accumulated research and practical experience, including study of links between ecosystem management and the historical principles of Chinese philosophy. The Bulgarian and European approach to ecosystem based management can benefit from analogies to TCM. We derive policy recommendations by analogy, and illustrate them on the example of Natural Capital Accounting., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Maintaining a strong antioxidant system is essential for preventing drought-induced oxidative stress. Thus, in the present study we investigated the role of some non-enzymic and enzymic antioxidants in desiccation tolerance of Haberlea rhodopensis. The effects of high light upon desiccation on antioxidant capacity was estimated by comparing the response of shade and sun plants. The significant enhancement of the antioxidant capacity at 8% RWC corresponded to an enormous increase in flavonoid content. The important role of ascorbate-glutathione cycle in overcoming oxidative stress during drying of H. rhodopensis was established. The antioxidant capacity increased upon dehydration of both shade and sun plants but some differences in non-enzymatic and enzymatic antioxidants were observed. Investigations on the role of polyphenols in desiccation tolerance are scarce. In the present study the polyphenol profiles (fingerprints) of the resurrection plant Haberlea rhodopensis, including all components of the complex are obtained for the first time. It was clarified that the polyphenol complex of H. rhodopensis includes only two types of glycosides - phenylethanoid glucosides and hispidulin 8-C-glucosides. Upon desiccation the polyphenol content increase and the main role of phenylethanoid glucosides in the protection of H. rhodopensis was revealed., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Effects of ozone on the sensitive tree species Fraxinus excelsior L. exposed to ambient air were investigated. The dynamics of photosynthesis, transpiration, stomatal conductance and the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in three-year-old ash seedlings were studied during a four-month period (June-September). Seedlings were exposed to ambient ozone in an urban (the Central City Park of Sofia - Borisova Gradina) and a mountain (Plana Mountain) area in Bulgaria. The sites were located near climate monitoring stations, providing data on ozone concentrations and meteorological parameters. Ozone exposure at the mountain site (AOT40) was more than two times higher compared to the urban site. Significantly higher values of sun radiation, transpiration, stomatal conductance and enzyme activity at the mountain site were also observed. At the urban site higher values of temperature and air humidity were registered. Effects of the measured variables on ash seedlings were complex and interdependent. No direct effect of ozone concentration in ambient air on the leaf physiology and biochemistry could be proved. However, intensified SOD and CAT activity in the presence of elevated ozone suggested antioxidant reaction in response to ozone uptake.

The aim of the present work was to study the response of two sunflower genotypes (cultivated sunflower Helianthus annuus cv. 1114 and newly developed genotype H. annuus × Helianthus argophyllus) to Pb medium-term stress and the role of exogenously applied EDTA in alleviating Pb toxicity in hydroponics. Plant growth, morpho-anatomical characteristics of the leaf tissues, electrolyte leakage, total antioxidant activity, free radical scavenging capacity, total flavonoid content, and superoxide dismutase isoenzyme profile were studied by conventional methods. Differential responses of both genotypes to Pb supplied in the nutrient solution were recorded. Pb treatment induced a decrease in the relative growth rate, disturbance of plasma membrane integrity, and changes in the morpho-anatomical characteristics of the leaf tissues and in the antioxidant capacity, which were more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype demonstrated higher tolerance to Pb when compared with the cultivar. This was mainly due to increased photosynthetically active area, maintenance of plasma membrane integrity, permanently high total antioxidant activity, and free radical scavenging capacity as well as total flavonoid content. The addition of EDTA into the nutrient solution led to limitation of the negative impact of Pb ions on the above parameters in both genotypes. This could be related to the reduced content of Pb in the roots, stems, and leaves, suggesting that the presence of EDTA limited the uptake of Pb. The comparative analysis of the responses to Pb treatment showed that the deleterious effect of Pb was more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype H. annuus × H. argophyllus was more productive and demonstrated higher tolerance to Pb medium-term stress, which could indicate that it may possess certain mechanisms to tolerate high Pb concentrations. This character could be inherited from the wild parent used in the interspecific hybridization. The ability of EDTA to prevent Pb absorption by the plants could underly the mechanism of limiting of the negative impact of Pb ions. Hence, EDTA cannot be used to enhance Pb absorption from nutrient solution by sunflower plants for phytoremediation purposes.

RNA-dependent DNA methylation (RdDM) is an important regulatory event involved in repressive epigenetic modifications that can trigger transcriptional gene silencing (TGS). The criteria we used to pick out promoter sequences targeted by RdDM in Arabidopsis thaliana were the main RdDM hallmark properties: 24nt siRNAs as inducers of DNA methylation and transposable elements (TE) as one of the major targets of RdDM. Those genes whose promoters comprised overlapping sites for 24nt siRNA hits, TE and DNA methylation (siRNA/TE/Methylation overlapping regions), were defined as candidates that might be silenced by RdDM. On this basis two gene sets were created which include abiotic and biotic stress-responsive genes whose promoters may be silenced by RdDM. The DNA methylation status of the At3g50770 (CML41) promoter - one of the selected candidates, was experimentally assayed, and it showed dependence on the RdDM-associated Polymerase IV and Polymerase V. A publicly available 24nt siRNA-centered database called starPRO was developed that allows users easily to discover whether a particular promoter sequence is related to RdDM-associated features such as 24nt siRNA-target sites, TE, tandem repeats and DNA methylation.

Darkness mediates different senescence-related responses depending on the targeting of dark treatment (whole plants or individual leaves) and on the organs that perceive the signal (leaves or cotyledons). As no data are available on the potential role of darkness to promote senescence when applied to individual cotyledons, we have investigated how darkness affects the progression of senescence in either a single or both individually darkened cotyledons of young 10-day-old Cucurbita pepo (zucchini) seedlings. Strong acceleration of senescence was observed when both cotyledons were darkened as judged by the damage in their anatomical structure, deterioration of chloroplast ultrastructure in parallel with decreased photosynthetic rate and photochemical quantum efficiency of PSII. In addition, the endogenous levels of cytokinins (CKs) and IAA were strongly reduced. In a single individually darkened cotyledon, the structure and function of the photosynthetic apparatus as well as the contents of endogenous CKs and IAA were much less affected by darkness, thus suggesting inhibitory effect of the illuminated cotyledon on the senescence of the darkened one. Apparently, the effect of darkness to accelerate/delay senescence in a single darkened cotyledon depends on the light status of the other cotyledon from the pair. The close positive correlation between CK content and the activity of CK oxidase/dehydrogenase (CKX; EC 1.4.3.18/1.5.99.12) suggested that CKX was essentially involved in the mechanisms of downregulation of endogenous CK levels. Our results indicated that CKX-regulated CK signaling could be a possible regulatory mechanism controlling senescence in individually darkened cotyledons.

The effect of exogenously applied silicon (Si) on plant growth, lipid peroxidation, total phenolic compounds and non-protein thiols was studied in two maize varieties (Zea mays L. vars. Kneja 605, 434) differing in sensitivity to excess manganese (Mn). Based on the density of brown spots per leaf area and relative shoot weight (RSW) used to define Mn tolerance var. Kneja 434 was found to be more Mn-tolerant than Kneja 605. The lipid peroxidation level and total phenolic compounds were enhanced with increasing Mn concentration in the nutrient solution. In addition, the Mn-sensitive var. Kneja 605 with markedly expressed first visible Mn toxicity symptoms had higher levels of total phenolic acids than var. Kneja 434 thus supporting the hypothesis that a stimulating effect of Mn on phenol content reflected rather a stress response to Mn excess than a tolerance mechanism. In contrast, non-protein SH content increased to a higher extent in the Mn-tolerant var. Kneja 434. The increased amount of non-protein SH compounds was accompanied by a much stronger oxidative stress in the Mn-sensitive plants when compared with the Mn-tolerant variety, thus suggesting that non-protein SH compounds may play a role in Mn tolerance in maize. The addition of silicon (Si) reduced the density of brown spots per leaf area as well as lipid peroxidation level and improved plant growth in Mn-treated plants.

Investigations were carried out on the basic and mineral composition of the liver of slaughtered birds. It was found that the water content of the liver depended on the age and sex, with broilers it being 73.09 g%, with laying hens--72.56 g%, and with cocks--70.62 g%. Proteins had highest percent in the liver of cocks, followed by those in the liver of hens, geese, broilers, and turkeys. The content of fats was highest in the liver of turkey, and in a descending order followed geese, broilers, hens, and cocks. Mineral salts varied from 1.20 to 1.35 g%; highest amounts of sodium were found in the liver of broilers, while highest levels of potassium, calcium, phosphorus, iron, zinc, and copper were established in the liver of turkeys.