Selenium is an essential trace element for animal and human beings. Despite the importance of insects in most ecosystems and their significant contribution to the biological cycling of trace elements due to high abundance, population productivity, and diverse ecosystem functions, surprisingly little information is available on selenium bioaccumulation by these arthropods. This review considers selenium essentiality and toxicity to insects as well as insects' contribution to selenium trophic transfer through the food chains. Data on Se accumulation by insects of the Dniester River Valley with no anthropogenic Se loading reveal typically low Se content in necrophagous insects compared to predators and herbivores and seasonal variations in Se accumulation.
Protection of plants against herbivorous pests is an important aspect that guarantees agricultural efficiency, i.e., food provision to populations. Environmental, water and foodstuff pollution by toxic pesticides, along with climate changes, highlight the necessity to achieve intensive development of ecologically safe methods of herbivory control. This review discusses modern methods of plant protection against insect pests: the biofortification of plants with selenium, treatment of plants with bulk and nano-silicon, and utilization of garlic extracts. The peculiarities of such methods of defense are described in relation to growth stimulation as well as increasing the yield and nutritional value of products. Direct defense methods, i.e., mechanical, hormonal, through secondary metabolites and/or mineral element accumulation, and indirect defense via predator attraction are discussed. Examples of herbivorous pest control during plant growth and grain/seed storage are emphasized. A comparison of sodium selenate, silicon containing fertilizer (Siliplant) and garlic extract efficiency is analyzed on Raphanus sativus var. lobo infested with the cruciferous gall midge Contarinia nasturtii, indicating the quick annihilation of pests as a result of the foliar application of garlic extract or silicon-containing fertilizer, Siliplant.
Biochemical and mineral peculiarities of plants inhabiting desert and semi-desert areas may provide important information about the mechanism of their adaptability and reveal the prospects of their utilization. Rheum tataricum L., known for its high tolerance to drought, salinity, and nutritional deficiency, is the least studied species of wild rhubarb. Using biochemical and ICP-MS analysis, the antioxidant status and mineral composition of R. tataricum were determined. Extremely high levels of antioxidant activity (148–155 mg GAE g−1 d.w.), polyphenols (24.6–25.1 mg GAE g−1 d.w.) and carotenoids (1.94 mg-eq β-carotene g−1 d.w.) were revealed in roots, proline in leaves (71.1 ± 6.2 mg kg−1 d.w.) and malic acid in stems (3.40 ± 0.50 mg g−1 d.w.). Compared to garden rhubarb, R. tataricum demonstrated significant root–leaves translocation of Li, Se, Si, and Mo, known to participate in plant antioxidant defense. Under high levels of Ca, Na, Mg, Fe, Cr and Si in soil, R. tataricum demonstrated the ability to significantly increase the accumulation of these elements in roots, showing a hyperaccumulation ability for Sr. The first broad picture of R. tataricum biochemical and mineral characteristics in semi-desert habitat and its nutritional value indicate the prospects of R. tataricum utilization in plant breeding, medicine, and nutrition.
The importance of using the barks of trees and shrubs as powerful natural antioxidants suggests the necessity to evaluate the effect of different environmental factors on bark extracts’ quality. The determination of total antioxidant activity (AOA) and polyphenol content (TP) in the bark of 58 tree and shrub species from 7 regions differing in mean annual temperature, insolation, humidity, salinity level, and altitude was performed. The above stress factors positively affected bark AOA but did not have a statistically significant effect on TP. The bark of trees grown in the seashore proximity was characterized by significantly higher AOA than samples gathered in other areas, similarly to the trees grown at high altitude. The bark antioxidant status of 18 species was described for the first time. New sources of powerful antioxidants were represented by the ornamental shrubs Cornus sanguinea and Cornus alba, which showed the highest AOA (169–171 mg GAE g−1 d.w.). Among the typical halophytes, Calligonum and Tamarix had high AOA (172 and 85 mg GAE g−1 d.w.), while in the bark of tamarisk, an Se accumulator, an Se concentration of about 900 µg kg−1 d.w. was recorded. A significant positive correlation was found between leaves and bark AOA in the Karadag Nature Reserve’s deciduous trees (r = 0.898, p < 0.01). The relationship between bark AOA and TP was highly significant (r = 0.809; p < 0.001) for all samples except the mountainous ones. The results of the present research revealed new opportunities in successive bark utilization.
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