Marieta Hristozkova

Antioxidant capacity of sage grown on heavy metal-polluted soil

Oxidative stress response and essential oil composition of sage (Salvia officinalis L.), grown on industrially polluted soil were studied. Sage plants were grown on the soil polluted with Cd, Cu, Pb, Zn, and non-polluted control soil. One-year-old sage possessed a high potential for heavy metal accumulation mainly in the roots. Heavy metal pollution resulted in root and shoot dry biomass inhibition. The increased levels of hydrogen peroxide and MDA showed that the heavy metal uptake caused oxidative stress. The increase towards the control was observed in the levels of glutathione, ascorbate, dehydroascorbate, catalase, dehydroascorbate reductase, and glutathione peroxidase. Weak activities of the most enzymes of the ascorbate-glutathione cycle allowed to suppose that H2O2 neutralization is rather non-enzymatic than enzymatic process. Observed decline in α- and β-thujones and elevated camphor content in the sage leaves did not indicate a deterioration of the essential oil quality. Sage grown on heavy metal-polluted soil successfully accumulated cadmium, lead, and zinc, which is resulted in plant biomass inhibition, but essential oil yield and quality was not declined.

Nitrogen Assimilatory Enzymes and Amino Acid Content in Inoculated Foliar Fertilized Pea Plants Grown at Reduced Molybdenum Concentration

ABSTRACT A possibility to improve nitrogen assimilation in nitrogen fixing Molybdenum (Mo) deficient pea plants was shown. The influence of foliar supplied nutrients in addition to root nutrition resulted in reducing the unfavorable effects of inorganic nitrogen on nodule function and Mo deficiency on the nitrogen assimilatory enzymes. Inoculated pea plants were grown on liquid nutrient solution both with and without Mo. The following variants were tested: Mo supplied plants with root nutrition (F1 + Mo); Mo supplied plants with root and foliar nutrition (F2 + Mo); Mo deficient plants with root nutrition (F1 − Mo); and Mo deficient plants with root and foliar nutrition (F2 − Mo). Foliar application of nutrients had a positive effect on the glutamine synthetase and glutamate synthase enzyme activities in the roots and nodules of Mo deficient plants. It was found that the foliar fertilization reduced the inhibitory effect of Mo shortage on the aspartate/asparagine content in the pea shoots.

EFFECT OF FOLIAR FEEDING ON NITROGEN ASSIMILATION IN ALFALFA PLANTS AT INSUFFICIENT MOLYBDENUM SUPPLY

The influence of foliar feeding on the nitrogen assimilation in alfalfa plants under conditions of Mo shortage was studied. It was established that foliar fertilization with 0.3% solution of Agroleaf® resulted in increase of nitrogen fixation and nitrogen assimilation in the absence of Mo. Insufficient molybdenum supply leads to significant reduction of plant Mo content and nitrogen-fixing activity, while stress induced amino acids as alanine, GABA, threonine, proline and serine increased repeatedly. The negative effect of Mo deficiency on the enzyme activities related to the primary nitrogen assimilation (NR, GS, GOGAT) and plant growth diminished due to the foliar absorbed nutrients.

Arbuscular mycorrhizal fungi enhance antioxidant capacity of in vitro propagated garden thyme (Thymus vulgaris L.)

Garden thyme (Thymus vulgaris L., Lamiaceae) is an important aromatic herb used for its medicinal values including antioxidant and antimicrobial properties. The present study was performed to analyze the changes in natural antioxidants after inoculation of in vitro propagated garden thyme plants with arbuscular mycorrhizal fungi (AMF). An efficient and low-cost protocol for large-scale multiplication of this aromatic plant was developed. The explants were cultured on full and half strength Murashige and Skoog (MS) medium containing indole-3-butyric acid (IBA). The maximum number of shoots and roots was obtained on ½ MS medium supplemented with 0.1xa0mg L−1 IBA after 4xa0weeks of culture. The successfully adapted in vitro plants (survival rate 95%) were inoculated with arbuscular mycorrhizal fungi (Claroideoglomus claroideum, ref. EEZ 54). Plants were then transferred into field conditions. Mycorrhizal fungi enhanced the activity of some soil enzymes, acid and alkaline phosphatase, urease as well as the levels of extractable glomalin-related proteins in plant rhizosphere. Arbuscular mycorrhizal associations with higher plants promote the accumulation of antioxidant metabolites such as phenols and flavonoids and increase the activity of antioxidant enzymes. The results from the present study suggest enhanced antioxidant capacity of the inoculated T. vulgaris plants which was due mainly to increased accumulation of phenolic compounds (total phenols and flavonoids) together with stimulation of the activity of superoxide dismutase (SOD) and guaiacol peroxidase (GPO).

Influence of Mycorrhizal Fungi and Microalgae Dual Inoculation on Basil Plants Performance

The rhizosphere microbial community is axa0complex of organisms interconnecting in multifold ways, acting upon each other and reacting to the surrounding environment. In the present research, we evaluated the influence of dual inoculation with arbuscular mycorrhizal fungi (AMF) and microalgae (Scenedesmus incrassatulus R83 and Synechocystis sp. R10) on basil plants performance. Different modes of basil inoculation (AMF, microalgae and axa0combination of both) were analyzed. We characterized AMF function (colonization and glomalin-related soil proteins), acid phosphatase activity (in root and soil), plant growth, photosynthetic parameters, secondary metabolites (fluorescence indices of leaf chlorophyll content; flavonols contents; nitrogen balance index), and the activity of plant enzymes linking nitrogen and carbon metabolism (glutamate synthase, aspartate aminotransferase and NADP-malic enzyme). The highest values of biometrical data were as axa0result of mycorrhiza application alone and in the mixed treatments with both microalgae strains. Dual inoculation with both microalgae and AMF, stimulated mycorrhizal function (concentration of glomalin-related proteins). Indexes of secondary metabolites (flavonols and anthocyanins) increased after treatment with Scenedesmus (Al1 and AMu202f+u2009Al1) compared to control plants. The addition of Synechocystis alone and in combination with fungi positively influenced nitrogen balance index. Different modes of inoculation increased gas-exchange parameters in all variations of inoculations compare to control plants. The results for activities of nitrogen-carbon metabolizing enzymes demonstrated close relationships with the plant growth. The mycorrhizal root colonization of basil may bear considerable economic importance. Thus, the addition of suitable AMF to the rhizosphere would significantly improve the growth and productivity of commercial Ocimum spp. cultivation.ZusammenfassungDie Mikrobengemeinschaft im Wurzelraum ist ein Komplex aus Organismen, die auf verschiedenste Weise miteinander verbunden sind, miteinander in Wechselwirkung stehen und auf ihre Umgebung reagieren. In der vorliegenden Studie wurde der Einfluss der Doppelinokulation mit Arbuskulären Mykorrhizapilzen (AMF) und Mikroalgen (Scenedesmus incrassatulus R83 und Synechocystis sp. R10) auf die Leistung von Basilikumpflanzen untersucht. Unterschiedliche Arten der Inokulation von Basilikum (AMF, Mikroalgen sowie eine Kombination aus beiden) wurden analysiert. Charakterisiert wurden die Funktion von AMF (Kolonisierung und Glomalin-verwandte Bodenproteine), die Aktivität saurer Phosphatase (in Wurzeln und im Boden), das Pflanzenwachstum, Photosyntheseparameter, sekundäre Metaboliten (Fluoreszenznachweis des Chlorophyllgehalts der Blätter, Flavonolgehalt, Stickstoffbilanz-Index) sowie die Aktivität von Pflanzenenzymen in der Verbindung des Stickstoff- und des Kohlenstoffmetabolismus (Glutamatsynthase, Aspartat-Aminotransferase und NADP-abhängiges Malatenzym). Die höchsten Werte dieser biometrischen Daten resultierten aus der Anwendung von Mykorrhiza allein sowie aus der gemischten Behandlung mit beiden Mikroalgenstämmen. Die doppelte Inokulation mit beiden Mikroalgen und AMF stimulierte die Mykorrhizafunktion (Konzentration Glomalin-verwandter Proteine). Die Indizes sekundärer Metaboliten (Flavonole und Anthocyane) stiegen nach der Behandlung mit Scenedesmus (Al1 und AMu202f+u2009Al1) im Vergleich mit Kontrollpflanzen. Die Zugabe von Synechocystis allein und in Kombination mit Pilzen hatte einen positiven Einfluss auf den Stickstoffbilanz-Index. Unterschiedliche Arten der Inokulation erhöhten Gasaustauschparameter in allen Variationen im Vergleich zu den Kontrollpflanzen. Die Ergebnisse zur Aktivität von Stickstoff-Kohlenstoff metabolisierenden Enzymen zeigten einen engen Zusammenhang mit dem Pflanzenwachstum. Die Wurzelbesiedelung von Basilikum mit Mykorrhiza könnte von beträchtlicher wirtschaftlicher Bedeutung sein. So würde die Zugabe geeigneter AMF in den Wurzelraum signifikant das Wachstum und die Produktivität im kommerziellen Anbau von Ocimum spp. verbessern.

Response of Vigna Unguiculata Grown under Different Soil Moisture Regimes to the Dual Inoculation with Nitrogen-Fixing Bacteria and Arbuscular Mycorrhizal Fungi

ABSTRACT The interaction between legumes, rhizobial and arbuscular mycorrhizal (AM) partners benefits plant nutrition and improves plant tolerance to water stress. The present research evaluated the effectiveness of symbioses between cowpea plants (Vigna unguiculata (L.) Walp.), AM fungi (Glomus intraradices) and two strains of Bradyrhizobium japonicum on the mycorrhization, acid phosphatase activity (APase), enzymes related to nitrogen fixation and assimilation, and biomass accumulation at three soil moisture levels. The results revealed that the soil moisture optimal for the formation of active symbiotrophic associations in cowpea cultivation was about 60% water-holding capacity (WHC), where both Bradyrhizobium strains and AM fungi function well with respect to mycorrhization, nitrogen and phosphorus uptake, nitrogen fixation and plant biomass production. Under conditions of reduced water supply, the symbiotic association between Br. japonicum-273 and Gl. intraradices was better for cowpea cultivation, while in elevated soil moisture association between Br. japonicum-269 and Gl. intraradices was more appropriate.

Regulation of Nitrogen Assimilation in Foliar Fed Legume Plants at Insufficient Molybdenum Supply

Formation and function of N2-fixing systems between bacteria from Rhizobiaceae family and legume plants from Fabaceae family are especially sensitive to molybdenum (Mo) deficiency. The hypothesis of the present work was that nitrogen fixation and assimilation in Mo deficient pea and alfalfa plants are enhanced when the nutrients were supplied through the foliage. It was established that foliar fertilization resulted in the increase of nitrogen fixation and biomass accumulation in the absence of Mo. The positive effect of foliar fertilization at insufficient Mo supply on the nitrogen uptake is better expressed in garden pea than in alfalfa. Otherwise, alfalfa was more sensitive to Mo starvation than the pea plants. Insufficient Mo supply leads to significant reduction in plant Mo content and nitrogen fixing activity, while stress induced free amino acids increased repeatedly. The negative effect of Mo exclusion from the nutrient media on nitrogen assimilation and biomass accumulation diminished through the foliar absorbed nutrients.