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Extreme environmental conditions are among the factors most frequently responsible for serious reduction in crop yield. Various abiotic stresses threaten wheat production worldwide and drought in particular is especially harmful when occurring at early vegetation phases. Four wheat varieties were compared with respect to their drought tolerance by withholding water in soil pot experiments and their ability to recover after re-watering was assessed based on changes in physiological and biochemical parameters. Drought caused significant decrease in leaf water content, increased the accumulation of hydrogen peroxide, malondialdehyde, free proline, and enhanced electrolyte leakage from cellular membranes. Water deprivation provoked oxidative stress which activated plants’ antioxidant defense system. The intensity of stress perception differed among the four wheat genotypes and they displayed diverse strategies for overcoming the imposed stress. While drought-resistant varieties responded to the stress via enhanced activity of ROS detoxifying enzymes, drought-sensitive genotypes employed coping mechanism involving accumulation of non-enzymatic components of the antioxidant defense system which were useful during the recovery process.

In order to develop an efficient micropropagation system, it is essential to establish the appropriate concentration of growth regulators for seed germination, shoot formation and rooting. Nodal segments from in vitro obtained seedlings of Gentiana lutea L. were cultured in vitro in Murashige and Skoog’s medium supplemented with BAP, Thidiazuron and Zeatin (0.5, 1.0 and 2.0 mg L−1). A maximum number of shoots with the highest height was recorded at 2.0 mg L−1 BAP. For further optimization of the process, we used nutrient media containing BAP and Zeatin with a combination of low concentration of Indoleacetic acid. MS medium containing 2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA resulted in maximum numbers of shoots 94.3) with shoot height 2.5 cm. The multiple plants were successfully ex vitro acclimatized with 65% survival. The presence of growth regulators (2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA) in the nutrient media resulted in an effective antioxidant activity in G. Lutea determined by the low molecular antioxidant metabolites such as phenols and flavonoids and activities of antioxidant enzymes – catalase, ascorbate peroxidase, guaiacol peroxidase, and superoxide dismutase. The described protocol allows the establishment of numerous micropropaged plants of rare and endangered G. lutea.

The effect of salinity on gas exchange and fluorescence characteristics in Lycium barbarum and Lycium chinense grown on nonsaline and saline soils was investigated. The distribution of Na+ between three types of substrates and different organs showed acropetal concentration gradient for Na+ accumulation only in L. barbarum grown on peat-moss-perlite and saline soil. Selective uptake of K+ over Na+ in the L. barbarum leaves was established. All plants grown on saline soil showed a slight inhibition of PSII activity as revealed by the quantum yield of the primary photochemical reaction. Intersystem electron transport, reduction of the end electron acceptors, and the performance index of photosynthesis declined to a greater extent in L. barbarum than that in L. chinense. The higher tolerance of L. chinense to salt stress was accompanied with the higher overall photosynthetic performance.

Interspecific cross was made between the common sunflower inbred line HA89 and an accession of wild Helianthus nuttallii (2n=2x=34) resistant to the most harmful disease complex and tolerant to drought and high temperature. The recombinant inbred line was a BC1F15 progeny. The most remarkable feature observed was the vigorous plant habit that manifests itself in measurable morphological characters such as increment plant height, stem diameter and diameter of the head. The line was non-branched (monocephalic) without anthocyanin pigmentation and possessed good agronomic characteristics. Along with the morphological and reproductive traits, some biochemical characteristics related to antioxidant activity were associated to wide hybridization. The overall characteristics of HA-Hnutt line make it a useful plant material for research on interspecific hybridization in Helianthus genus.

The rhizosphere microbial community is a complex 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 a combination 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 a result 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 AM + Al1) 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.

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 0.1 mg L−1 IBA after 4 weeks 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).

A pot experiment was carried out to investigate the effect of salinity on growth, leaf anatomy and gas exchange characteristics in two Paulownia hybrid lines (Paulownia tomentosa × fortunei-TF and Paulownia elongata × elongata-T4). The distribution of Mg, Ca, Na, K and Fe between water available fractions from non-saline, saline soils, and different organs showed acropetal concentration gradient for metal accumulation, excepting Ca. Selective uptake of K over Na was enhanced slightly with increasing salinity, where K/Na ratio was reduced in Paulownia elongata × elongata-T4 and rose in Paulownia tomentosa × fortunei-TF. The reduction in the total plant leaf area and in the values of the intrinsic components of photosynthesis-maximal Rubisco catalyzed carboxylation velocity, maximal electron transport rate and triose phosphate utilization rate was observed only in Paulownia tomentosa × fortunei-TF. The CO2 compensation point rose to Paulownia tomentosa × fortunei-TF and declined in Paulownia elongata × elongata-T4, while the stomatal factor values were enhanced in both hybrid lines. Under saline conditions, the stomatal component was more limiting to photosynthesis than its biochemical components. It was concluded that Paulownia elongata × elongata-T4 was more resistant to salinity because its growth and gas exchange characteristics were less affected in comparison with Paulownia tomentosa × fortunei-TF.

The mycorrhizal fungi community is a significant soil rhizosphere component that benefits plant nutrition and improve plant tolerance to abiotic stresses. The present research compared the influence of three mycorrhizal strains over pot marigold ( Calendula officinalis L.) development and their contribution to promoting the valuable secondary metabolites accumulation in the condition of heavy metal (Cd and Pb) pollution. Two Claroideoglomus claroideum isolates (from industrially and naturally enriched metal-contaminated sites) and Funneliformis mosseae (derived from a soil with a high concentration of various metals) were studied. The mycorrhizal status and acid phosphatase activity were best exposed in the roots associated with C. claroideum (from native metalliferous sites) and corresponded with the highest total phenols and flavonoids concentrations. Neither Pb nor Cd was detected in the marigold flowers ( Calendula flos drug) following targeted mycorrhizal treatment. The higher Cd and Pb levels in non-mycorrhizal plants lead to the lowest flower weight, but in the aerial plant parts, we found a slight distinction. The tested strains stimulated the accumulation of important secondary metabolites (total phenols, flavonoids, carotenoids) in pot marigold flowers and, therefore, enhanced the antioxidant capacity. The carotenoid profile of mycorrhizal plants performed notable differences between the primarily defined constituents (lutein, lycopene, β-carotene). The highest β-carotene values (respectively vitamin A) and lycopene were found in pot marigold— F. mosseae association. The findings are essential to obtain the optimum benefits of mycorrhizal association in unfavorable conditions concerning pot marigold bioactive compounds synthesis.

Background Tayberry is a hybrid between Rubus fruticosus L. and Rubus idaeus L. These fruits contain valuable vitamins and antioxidants. An effective protocol for micropropagation of tayberry plants is here described. Different concentrations of cytokinins (6-benzylaminopurine, zeatin, and 6-(γ,γ-dimethylallylamino)purine) were added in Murashige and Skoog, 1962 (MS) medium to micropropagation using stem tip and nodal explants. Results The highest propagation rate was recorded on MS medium containing 2 mg L(-1) zeatin, where the shoot formation resulted in 3.4 shoots per stem tip explant after 4 weeks of culture. It was found that half-strength MS medium with 0.1 mg L(-1) indole-3-butyric acid was the best for plant rooting. For ex vitro acclimatization of plants, the mixture of peat, soil, and perlite (1:1:1 v/v/v) was the most suitable planting substrate for hardening. The micropropagation protocol described in this study might be useful for the production of healthy plant materials. Tayberry fruits from in vitro propagated plants and adapted to the field conditions possessed higher antioxidant capacity in comparison to traditionally cultivated plants. Conclusion Fruit extracts of micropropagated tayberry plants and adapted to field conditions can be used as a rich source of natural antioxidants. © 2015 Society of Chemical Industry.

Essential oil quality, quantity, and antioxidant capacity of foliar fertilized Matricaria recutita L., grown on industrially polluted with cadmium (Cd) and lead (Pb) soil were studied. The polluted field is near the waste depository of ferrous metallurgical combine “Kremikovci”. Content of Cd and Pb in the soil exceeded permissible concentrations 4.6 and 2.0 times, respectively. The presence of high levels of heavy metals in the soil resulted in retained plant growth. In M. recutita grown on industrially polluted soil, a decrease of root and shoot dry biomass and reduction of number of lateral steams was observed. Otherwise, the number and biomass of flowers per plant increased. Antioxidant defense in the foliar fertilized plants grown on industrially polluted soil could due mainly to increased levels of peroxidases with substrates ascorbate, glutathione, guaiacol, and hydrogen peroxide. Enhanced levels of Cd and Pb in soil did not influence essential oil yield and quality of chamomile.

The effects of Cd, Pb, and Zn uptake on plant morphology, photosynthetic parameters, antioxidant potential, and essential oil yield and quality in Ocimum basilicum L. and Origanum vulgare L. plants were evaluated. The plants were grown as a pot experiment in soil heavily polluted with Cd and Pb and on unpolluted soil. Both plants accumulated Cd, mainly in the roots, while Pb occurred in the oregano shoots only. The leaf blade thickness of both plants increased when grown in polluted soil. Basil plants responded to the action of heavy metals with increases in gas exchange, stomatal conductivity, and transpiration, but water-use efficiency declined. Gas exchange and transpiration were reduced in treated oregano plants, but stomatal conductivity and water-use efficiency increased significantly. In basil, the increased levels of low molecular weight antioxidants such as phenols and flavonoids were observed, while in oregano, ascorbate, glutathione, and phenols were enhanced. Enzymatic antioxidant defense was observed in both plants when grown in contaminated soil, mainly with glutathione peroxidase, quaiacol peroxidase, glutathione S-transferase, and glutathione reductase. Accumulated levels of Cd, Pb, and Zn in plant organs resulted in a reduction in essential oil yield in basil only.

The effects of EDTA application to heavy metal-polluted soil on phytoextraction of heavy metals, leaf anatomy, gas exchange parameters, enzyme activities of C4 carbon cycle, antioxidant defense, and active compounds of Tribulus terrestris L. were evaluated. The addition of EDTA to the soil polluted with Cd and Pb markedly increased dry weight and Pb, Zn, and Cd contents in shoots. Plants responded to the action of EDTA by an increased stomatal conductance, photosynthetic and transpiration rates, water use efficiency, chlorophyll and carotenoid contents. The activities of C4 carbon cycle enzymes simultaneously increased, thus concentrating CO2 for enhanced CO2 assimilation and providing NADPH for the antioxidant system. Antioxidants, such as ascorbate, reduced glutathione, and flavonoids, increased more in the shoots of T. terrestris after the addition of EDTA. The activities of guaiacol peroxidase, catalase, and the enzymes of the ascorbate-glutathione cycle enhanced significantly in the presence of EDTA. Increased activities of antioxidant enzymes suggest that they have some additive functions in the mechanism of metal tolerance. EDTA application lowered the activity of phenylalanine ammonia-lyase and the content of total phenols, MDA, hydrogen peroxide, dehydroascorbate, and lipid-soluble antioxidant capacity expressed as α-tocopherol. Increased levels of total radical-scavenging activity are in correspondence with the activity of water-soluble antioxidant compounds in T. terrestris tissues. The content of furostanol saponins protodioscin, prototribestin, and rutin increased as a result of EDTA addition. The results obtained allowed us to assume that applied EDTA reduced a negative heavy metal impact on puncture vine photosynthesis and antioxidant potential.

An effective in vitro protocol for rapid clonal propagation of Echinacea purpurea (L.) Moench through tissue culture was described. The in vitro propagation procedure consisted of four stages: 1) an initial stage - obtaining seedlings on Murashige and Skoog (MS) basal medium with 0.1 mg L−1 6-benzylaminopurine, 0.1 mg L−1 α-naphthalene acetic acid and 0.2 mg L−1 gibberellic acid; 2) a propagation stage — shoot formation on MS medium supplemented with 1 mg L−1 6-benzylaminopurine alone resulted in 9.8 shoots per explant and in combination with 0.1 mg L−1 α-naphthalene acetic acid resulted in 16.2 shoots per explant; 3) rooting stage — shoot rooting on half strength MS medium with 0.1 mg L−1 indole-3-butyric acid resulted in 90% rooted microplants; 4) ex vitro acclimatization of plants. The mix of peat and perlite was the most suitable planting substrate for hardening and ensured high survival frequency of propagated plants. Significant higher levels were observed regarding water-soluble and lipid-soluble antioxidant capacities (expressed as equivalents of ascorbate and α-tocopherol) and total pnenols content in extracts of Echinaceae flowers derived from in vitro propagated plants and adapted to field conditions in comparison with traditionally cultivated plants.

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.

The effects of foliar fertilization and a growth regulator 5-tert-butyl-N-m-tolylpyrazine-2-carboxamide (MD148/II) on the growth, seed yield, and silymarin content of milk thistle (Silybum marianum Gaertn.) plants were evaluated. The study was conducted over two years at an experimental field on a slightly acid-leached cinnamonic meadow soil. The MD148/II was applied in the beginning of milk thistle flowering stage. Foliar fertilizer was applied at different plant developmental stages with different proportions of nitrogen (N), phosphorus (P), and potassium (K). Treatments with foliar fertilizer and MD148/II resulted in improvement of plant biomass, number of plant lateral shoots, flowering rate, and seed yield and the content of some active substances in milk thistle seeds. A reduction of high molecular fatty acids was observed. The increase of seed yield was a result of the flower head setting enhancement. Therefore the combined treatment of foliar fertilizer and MD148/II was efficient in elicitation mi...

The essential oil yield and chemical composition of Salvia officinalis L. (Dalmatica origin) have been analyzed. Leaf samples for essential oil analysis were harvested at different developmental stages after treatment with foliar fertilizer Agroleaf® and foliar fertilizer + thidiazuron. In total, 10 constituents were identified and quantified. The main compounds in the essential oil that increased during the vegetative to the fruiting‐set stage are α‐thujon and camphor, whereas borneol, viridoflorol, and manool decreased. The effect of thidiazuron applied together with foliar fertilizer was established mainly at the flowering stage, increased essential oil yield by 16% over the control, and positively affected the percentage of β‐caryiophylene, α‐humulene, viridoflorol, and manool. Application of foliar fertilizer resulted in a greater increase of essential oil yield at the flowering stage in the combined foliar and thidiazuron application over the control. Both treatments decreased camphor at flowering a...

The influence of the EDTA and citrate addition to the industrially polluted soil on phytoextraction of heavy metals, leaf anatomy, and gas exchange parameters of two Paulownia hybrid lines (Paulownia tomentosa x fortunei - TF 01 and Paulownia elongata x fortunei - EF 02) was evaluated. Both lines were accumulators of Cu, Zn and Cd because bioaccumulation factor values were higher than 1.00. The levels of heavy metal accumulation in shoots allowed supposing that both hybrids may be used for phytoremediation since transfer factors for Pb and Zn in hybrid - TF 01 were higher than 1.00, while in hybrid - EF 02 - for Zn only. Application of EDTA produced heavy metal accumulation in hybrid lines higher than those obtained with citrate. Treatment with 1 mM EDTA displayed a protective effect on leaf development in both lines and overcame damages in its morphological structure caused by heavy metal stress.

An efficient method for the micro propagation of hyssop (Hyssopus officinalis L.) has been developed. The plants were cultured on Murashige and Skoog's medium supplemented with 6-benzyl-aminopurine, thidiazuron, zeatin and indole-3butyric acid after four weeks of culture. Maximum numbers of shoots, shoot length, fresh weight and dry weight were established at 1.0 mg/L 6-benzyl-aminopurine and 0.1 mg/L indole-3-butyric acid. For induction of root, uniform micro shoots were excised and transferred to the rooting medium (half strength Murashige and Skoog medium macro and microelements) supplemented with 0.1 mg/L indole-3-butyric acid and 20 g/L sucrose. Indole-3-butyric acid increased culture rooting, number of roots and root length more efficiently at 0.1 mg/L after four weeks of culture. The multiple plants were successfully ex vitro adapted with 90% survival. The described protocol allows the establishment of numerous micro propagated plants of H. officinalis. The used growth regulators for hyssop micro propagation influenced plant antioxidant system. Antioxidant defence of micropropagated H. officinalis determined by the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) resulted in higher shoot formation and increasing of shoot number per explant.

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.

Two months-old sage seedlings were grown during 10 weeks on the soil/sand substrate in the ratio 3:1. The soil was collected from the vicinities of a Non-Ferrous Metals Combine near Plovdiv with pH (H2O)–7.35 and the following content of heavy metals (μg g−1DW): Cd - 9.02±0.98, Cu- 82.10±3.69, Pb- 301.75±21.03, Zn- 641.60±35.89. For the control non-polluted leached cinnamonic forest soil (Chromic Luvisols—FAO) was used. Heavy metal pollution with Cd, Zn and Pb resulted in 15% root dry biomass inhibition and 10% shoot dry biomass inhibition. Cd, Pb and Cu were accumulated previously in the sage roots, while Zn was accumulated both in the roots and shoots. In total, 11 constituents of the sage essential oil were identified and quantified. Because of the shoot dry biomass inhibition percentage of the essential oil yield towards dry biomass increased under conditions of heavy metals pollution. The main compounds in the essential oil that decreased as a result of heavy metals pollution are α-thujon, β-...

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.

Two important enzyme in organic acid metabolism, phosphoenolpyruvate carboxylase (PEPC) and NADP-malic enzyme (NADP-ME), show marked diurnal rhythms in their activities during the establishment of the soybean - B. japonicum symbiosis. The pH of the nutrient solution changes in parallel with NADP-ME activity, being maximal during the night periods, whereas activity of PEPC was highest during the day periods. The results from the experiments with stem girdled plants indicated that the activity of root PEPC is modulated to a great extent by the supply of photosynthates from the shoots. It was also established that succinate application in the nutrient solution during inoculation altered significantly the pattern of assayed enzyme activities. Although our experiments did not reveal the precise mechanism of the involvement of root PEPC and NADP-ME in soybean response to inoculation with B. japonicum, they indicated the pattern of their activity during the first 72 h postinoculation which are critical for establishment and functioning of the symbiosis.

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.