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Flame-weeding is a very useful method for weed control, especially in organic production where the use of herbicides is prohibited. With this method heat sup­presses weeds in row within a second. Apart from this, heat also affects growing crop plants and surrounding soil. The aim of this paper was to determine the effect of different propane doses, on photosynthetic and polyphenolic (total flavonoids and anthocyаnins) pigments in soybean leaves, as well as the number of microorganisms in the soil. Soybean plants exposed to flame showed a different reaction to high temperature stress, which was reflected in differ­ent content of analyzed biochemical parameters, but the most responsive were anthocyanins. Actinomycetes turned out to be the most sensitive group of soil microorganisms affected by weed flaming, while fungi were the most tolerant.

The purpose of this study was to analyze antioxidant systems among three invasive ragweed species, Ambrosia artemisiifolia L., A. trifida L. and Iva xanthifolia Nutt. Antioxidant capacity could be a possible marker of adaptation to variable environmen­tal conditions, since change in amount of antioxidants represents one of the first responses to various environmental stimuli. Among investigated ragweeds, I. xanthifolia leaves had more pronounced guaiacol peroxidase activity (87.5 and 62.5%) and reduced glutathione content (2.3 and 28.8%) than A. artemisiifolia and A. trifida, respectively. However, super­oxide dismutase activity was invariable in all investigated plants (234.1-247.5 U g-1 fresh weight). The highest content of total phenolics, tannins, flavonoids and proanthocyanidins were detected in A. trifida leaves (up to 3.7 - fold the amount of the others). According to antioxidant activity tests, investigated ragweed species could be presented in a scale: A. trifida > I. xanthifolia > A. artemisiifolia. Accumulation of non-enzymatic antioxidants and lower content of reduced glutathione point to different oxidative stress avoidance strategies of A. trifida when compared to A. artemisiifolia and I. xanthifolia within the same environ­mental conditions.

Plants which belong to Lamiaceae family are good potential sources of natural antioxidants useful for preventing oxidative stress-related diseases. The food industry is becoming increasingly interested in aromatic herbs, including plants from Lamiaceae family, because of their anti-inflammatory properties and antioxidant activities, due to growing consumer demands for healthy foods of natural origin. In the present investigation, the comparative antioxidant potential of aqueous and acetone extracts of three Lamiaceae species are described: Clinopodium menthifolium (Host), Satureja montana L., and Salvia sclarea L., using three methods: 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) radical (ABTS) scavenging, 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH) scavenging, and ferric reducing antioxidant power (FRAP) assay and their correlations with total phenolic and flavonoid contents. Antioxidant capacity showed a positive relationship comparing three above mentioned tests. Antioxidant capacity detected by antioxidant ABTS, DPPH, and FRAP assays was positively correlated with total phenolics content. Aqueous extract of C. menthifolium showed greater antioxidant potential.

This study was conducted in order to assess the effect of inoculation of soybean (Glycine max L.) seeds with Trichoderma asperellum, followed by mites (Tetranychus urticae) exposure on lipid peroxidation (LP) process and the activity of antioxidant enzymes. T. urticae is an occasional pest of soybean that causes biotic stress. Biotic stress leads to overproduction of reactive oxygen species (ROS) which may cause damage to vital biomolecules. Enzymatic antioxidant defense systems protect plants against oxidative stress. T. asperellum is commonly used as biocontrol agent against plant pathogens. It has been suggested that previous inoculation of seeds with T. asperellum may cause induced resistance against biotic stress. The aim of this study was to determine LP intensity and antioxidant enzymes activity in inoculated and non-inoculated soybean seedlings with and without exposure to mites. Noticeably higher LP intensity was detected in non-inoculated group treated with mites compared to control group. Inoculated soybean seedlings treated with mites had lower LP intensity compared to noninoculated group. Also, it has been noticed that inoculation with Trichoderma asperellum itself, produced mild stress in plants. In addition, positive correlation between enzymes activity and LP was noticed. The level of oxidative stress in plants was followed by the change of LP intensity. According to results obtained, it was concluded that the greatest oxidative stress occurred in non-inoculated group treated with mites and that inoculation successfully reduced oxidative stress. The results indicate that inoculation of soybean seeds with T. asperellum improves resistance of soybean seedlings against mites attack. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR-31022]

Secondary plant biomolecules are the main agents in biochemical inter­actions between plants and the environment. It is possible to distinguish the role of secondary biomolecules in allelopathic (plant-plant) activity, plant-insect, plant-microbe, plant-herbivore and others. These interactions can significantly affect the productivity of agricultural crops. Application of allelochemicals into agricultural practice may reduce the use of herbicides. Effect of Salvia sclarea L. and Clinopodium menthifolium (Host) aqueous extracts on lipid peroxidation process, as well as the activity of antioxidant enzymes in leaves and roots of Jimson weed (Datura stramonium L.) and soybean (Glycine max L.) seedlings were examined 24 h, 72 h and 120 h after the treatment. The third aim was to evaluate effectiveness of aqueous extract as contact toxicant against Rhyzopertha dominica. Our results showed that S. sclarea aqueous extract induced lipid peroxidation in roots of Jimson weed seedlings 24 h after the treatment. Furthermore, both tested concentrations of C. menthifolium aqueous extract induced lipid peroxidation in Jimson weed roots 72 h and 120 h after the treatment. It was observed that S. sclarea aqueous extract showed toxic effect against R. dominica, with high mortality rate (above 95%).

Nitrate reductase and glutamine synthetase activity, as well as free proline and soluble protein content were measured in eight soybean parent genotypes and six F1 hybrids. The aim of this study was to determine variability and the mode of inheritance for these parameters, and point out the genotypes of interest for future breeding programs. Analysed genotypes and their F1 hybrids expressed significant differences in activities of nitrate reductase and glutamine synthetase enzymes, as well as in soluble proteins and free proline contents. Since mode of inheritance for all investigated traits was in most cases dominance or heterosis, it can be concluded that these parameters are under control of dominant genes. The obtained results suggest that genotypes with favorable traits, such as variety Linda, line 1511, and F1 hybrids (Linda x LN92-7369) and (Balkan x BL-8), could be of interest as a good starting material for further breeding programs.

Composition of mineral elements has been investigated in three Salvia species (Lumiaceae) growing wild in the Vojvodina Province (Serbia), as well as in a commercial phytopreparation (tea) of Salvia officinalis L. We determined concentrations of micro- and macroelements in dried plant material in order to evaluate their nutritive and medicinal value and to indicate an easily accessible natural source that could be used as a possible food supplement. The study showed that the plants were well supplied with essential elements. Concentrations of potentially harmful heavy metals (Pb, Cd, Ni, Cr) were below their respective toxic levels. From the nutritive and medicinal aspects, the investigated Salvia species may be considered as a natural source of essential microelements, especially Fe and Cu, with a low capacity for heavy metal accumulation.