Effect of different proportion of sulphur treatments on the contents of glucosinolate in kale (Brassica oleracea var. acephala) commonly consumed in Republic of Korea

Kale (Brassica oleracea L. Acephala Group) is the rich source of medicinal value sulphur compounds, glucosinolates (GLSs). The aim of this study was to investigate the effect of different proportion of sulphur (S) supplementation levels on the accumulation of GLSs in the leaves of the kale cultivar ('TBC'). High performance liquid chromatography (HPLC) separation method guided to identify and quantify six GSLs including three aliphatic (progoitrin, sinigrin and gluconapin) and three indolyl (glucobrassicin, 4-methoxyglucobrassicin and neoglucobrasscin) respectively. Analysis of these distinct levels of S supplementation revealed that the accumulation of individual and total GLSs was directly proportional to the S concentration. The maximum levels of total GLSs (26.8 µmol/g DW) and glucobrassicin (9.98 µmol/g DW) were found in lower and upper parts of the leaves supplemented with 1 mM and 2 mM S, respectively. Interestingly, aliphatic GSLs were noted predominant in all the parts (50.1, 59.3 and 56% of total GSLs). Among the aliphatic and indolyl GSLs, sinigrin and glucobrassicin account 35.3 and 30.88% of the total GSLs. From this study, it is concluded that supply of S enhance the GSLs accumulation in kale.     

Combined effect of Nitrogen,Phosphorus and Potassium fertilizers on the contents of glucosinolates in rocket salad (Eruca sativa Mill.)

Nitrogen (N), phosphorous (P) and potassium (K) are the most limiting factors in crop production. N often affects the amino acid composition of protein and in turn its nutritional quality. In Brassica plants, abundant supply of N fertilizer decreases the relative proportion of glucosinolates (GSLs), thus reducing the biological and medical values of the vegetables. Hence effort was made to evaluate the influence of different proportions of nutrient solutions containing N–P–K on the GSL profiles of rocket salad (Eruca sativa Mill.). Fifteen desulpho-(DS) GSLs were isolated and identified using liquid chromatography–mass spectrometry (LC/MS) analysis. Rocket salad plants supplied with lesser amount of N, P or higher concentrations of K showed a typical improvement in total GSL contents. In contrast, total GSL levels were less at higher N supply. Furthermore, with N concentrations above 5 mM and K concentrations less than 2.5 mM, the GSL amounts were on average 13.51 and 13.75 μmol/g dry weight (DW), respectively. Aliphatic GSLs predominated in all concentrations of NPK while indolyl GSLs made up marginally less amount of the total compositions. Five and 2 mM N and P possessed much higher levels of several types of aliphatic GSLs than other concentrations, including glucoerucin, glucoraphanin and dimeric 4-mercaptobutyl GSL. From this perspective, it is contended that supply of less N results in enhancing the metabolic pathway for the synthesis of GSLs in rocket salad.     

Glucosinolate profiling of Brassica rapa cultivars after infection by Leptosphaeria maculans and Fusarium oxysporum

The glucosinolate contents of two different cultivars of Brassica rapa (Herfstraap and Oleifera) infected with Leptosphaeria maculans and Fusarium oxysporum were determined. Infection triggered the accumulation of aliphatic glucosinolates (gluconapin, progoitrin, glucobrassicanapin and gluconapoleiferin) and indole glucosinolate (4-hydroxy-glucobrassicin) in Herfstraap and of two indole glucosinolates (glucobrassicin and 4-hydroxy-glucobrassicin) in Oleifera. While total and aliphatic glucosinolates decreased significantly in Oleifera, a large increase was observed in Herfstraap after fungal infection. The indole glucosinolate glucobrassicin accumulated in Oleifera at a higher rate than Herfstraap especially after infection with F. oxysporum. Apparently the interaction between fungus and B. rapa is cultivar and fungal species specific.     

Effect of arsenic on visible symptom and arsenic concentration in hydroponic Japanese mustard spinach

Responses of Japanese mustard spinach (JM-spinach; Brassica rapa L. var. pervirdis) were investigated at elevated levels of arsenic (As). Plants were grown hydroponically in the greenhouse under 0, 6.7, 33.5 and 67 μM As (equal to 0, 0.5, 2.5 and 5 mg L^?1 As, respectively) for 14 days. Arsenic was used as sodium meta-arsenite (NaAsO₂). Toxicity symptom was solely shown as shoot growth repression at 33.5 and 67 μM As exposures. Dry weight (DW) enhanced by 19.4% in shoot and 38.9% in root in the 6.7 μM As level as compared to control but decreased by 48.1% and 72.1% DW in shoot and 24.1% and 61.1% DW in root in the 33.5 and 67 μM As levels, respectively. This result indicated that As at lower concentration might have slight stimulating effect on JM-spinach growth, but toxicity increased with increasing As. Based on the regression lines between growth and As concentration in the plant tissues, the critical toxicity level (CTL) of As in JM-spinach shoot was 7.85 μg g^?1 DW considering 10% DW reduction. The CTL for the root was almost 2110 μg As g^?1 DW, indicating that shoot of JM-spinach was more sensitive to As-toxicity than that of root. Arsenic concentrations increased in plant parts with increasing As in the medium. Arsenic concentrations were also compared in DW and fresh weight (FW) basis. The JM-spinach concentrated unaccepted level of As in shoots for human consumption in the higher As levels without showing visible toxicity symptom. In spite of decreasing iron (Fe) concentration in shoot in the highest As level, chlorophyll index did not decrease accordingly. Phosphorus (P) concentration also decreased. Phosphorus concentration decreased much more than Fe concentration. Low P might help to mobilize Fe in shoots, resulting in higher chlorophyll index at 67 μM As level. Phosphorus might compete with Fe in shoot tissues of As-stressed JM-spinach.     

Phytochemical and antioxidant properties of unconventional leafy vegetables consumed in southern Africa

Indigenous leafy vegetables possess high horticultural potential based on their long utilisation history by local communities across Africa. Phytochemical and antioxidant properties of 50% aqueous methanol and water extracts of three indigenous as well as two commercial leafy vegetables commonly consumed in southern Africa were evaluated. The total extractable phenolic content was highest for Amarathus dubius (5.16 ± 0.12 mg GAE/g DW) followed by Cleome gynandra (3.94 ± 0.09 mg GAE/g DW). Total flavonoid concentration was highest for A. dubius (3.89 ± 0.28 mg CE/g DW) followed by C. gynandra (2.19 ± 0.11 mg CE/g DW) and Cucurbita maxima (1.55 ± 0.04 mg CE/g DW). No proanthocyanidins were detected in C. maxima and Brassica napus cv Covo whereas low concentrations were recorded in other vegetables. Total saponins were variable across the evaluated extracts, with the highest concentrations recorded for B. napus cv Covo (83.2 ± 16.58 mg DE/g DW). Total iridoid content was highest for C. gynandra (9.14 ± 0.20 mg HE/g DW). More potent DPPH radical scavenging activities were exhibited by 50% aqueous methanol extracts compared to water extracts. A similar trend was observed in the ferric-reducing antioxidant power assay. The antioxidant activity based on the rate of β-carotene bleaching was higher for water extracts compared to 50% aqueous methanol extracts. The indigenous vegetables evaluated in this study had higher levels of phytochemicals and also exhibited more potent antioxidant activity compared to the commercial varieties. These findings not only suggest the importance of the indigenous vegetables in a healthy diet, but also provide a motivation for exploring their horticultural potential.     

GM risk assessment: Pollen carriage from Brassica napus to B. rapa varies widely between pollinators

Characterizing insect pollen carriage between closely related plant species is especially challenging where source species possess morphologically identical pollen and share many pollinators in common. Here, we use an SNP-based assay using the plant DNA barcoding locus matK to characterize pollen carriage between cultivated Brassica napus and wild Brassica rapa in three sites across southern England. The assay differentiated B. napus and B. rapa pollen carried by honey bees (Apis melifera), bumblebees (Bombus spp.), mining bees (Andrena spp.) and hoverflies (Syrphidae) captured on B. napus plants 1–2 m from wild B. rapa, and on B. rapa plants at various distances from the crop . Apis individuals foraging on B. rapa and carrying B. napus pollen were rarely found beyond 10 m from the crop. However, Bombus and Andrena individuals captured on B. rapa occasionally carried crop pollen up to 300 m from the source field. Hoverflies carried less pollen overall but featured high proportions of B. napus pollen even at the most distant capture points. We predict that different pollinator species will evoke markedly different patterns of interspecific hybrid formation. We conclude that more exhaustive surveys of this kind will help parameterize future mechanistic models to predict the distribution of hybrids between Genetically Modified B. napus and B. rapa on a landscape scale.     

Variation in polyphenolic profile and in vitro antioxidant activity of eastern teaberry (Gaultheria procumbens L.) leaves following foliar development

Seasonal dynamics in the polyphenolic composition, antioxidant activity, and their relationships during plant development were evaluated for eastern teaberry (Gaultheria procumbens L.) leaves, a traditional herbal medicine of North American natives. With the complementary UHPLC-PDA-ESI-MS³, HPLC-PDA-fingerprint, Folin-Ciocalteau, and n-butanol/HCl assays of methanol-water (75:25, v/v) extracts, the dried leaf samples harvested monthly across the growing season under Polish climate conditions were found rich in structurally diverse polyphenols (149.2–210.7 mg/g DW) including the dominating salicylates (64.6–107.5 mg/g DW), proanthocyanidins (53.0–66.8 mg/g DW), and flavonoids (17.3–25.3 mg/g DW), and the accompanying chlorogenic acid isomers (2.4–4.4 mg/g DW) and simple phenolic acids (0.9–1.1 mg/g DW). Among 28 detected analytes, gaultherin (64.6–107.5 mg/g DW), miquelianin (14.6–21.1 mg/g DW), procyanidin A-type trimer (5.5–9.5 mg/g DW), and (–)-epicatechin (5.8–7.8 mg/g DW) were the most abundant. The phenolic levels and antioxidant activity parameters in the DPPH (EC₅₀, 15.0–18.2 μg DW/mL; 0.95–1.16 mmol Trolox equivalents/g DW) and FRAP (2.3–3.4 mmol Fe ²⁺/g DW; 0.86–1.26 mmol Trolox equivalents/g DW) assays showed parallel seasonal trends with maxima in September and October. As the subsequent correlation studies confirmed the determinative impact of polyphenols on the leaf antioxidant activity and its seasonal fluctuations, the Fall season could be recommended as optimal for harvesting the plant material for medicinal purposes and cost-effective production of natural health products.     

Impacts of monosodium glutamate industrial wastewater on plant growth and soil characteristics

Research into utilization of monosodium glutamate industrial wastewater (MSGW) as a plant nutrient source was undertaken. The physico-chemical and microbiological characteristics of MSGW were analyzed in detail. Effect of MSGW on early growth of Chinese cabbage (Brassica rapa L. cv. Pekinensis) and maize (Zea mays L. cv. Bright Jean) was tested by the seed germination bioassay. Subsequently, in a greenhouse pot experiment using the same plant species, effects of MSGW application rates on the plant biomass yield, nitrogen content and soil properties were analyzed. The MSGW was characterized by high levels of N (56.7 g l^?1), organic C (344.6 g l^?1), total solids (600 g l^?1) and other minerals. At MSGW concentrations below 1%, germination indices for both the plant species were significantly (p < 0.01) higher than the control. Further, the greenhouse study results indicated significant increase in the plant biomass yield at MSGW application rates of 5000 and 7500 l ha^?1. As the MSGW dose increased, the biomass yield decreased, decreasing the N-use efficiency. Maize showed significantly higher wastewater N-use efficiency compared to the Chinese cabbage. Although the total culturable bacterial and fungal counts in the raw MSGW were low, addition of MSGW to the soil increased the soil microbial activities and soil respiration. Soil organic C was also increased by the addition of MSGW, due to the presence of significant amounts of organic C in the wastewater. This preliminary study demonstrates that by proper management of the pH and optimization of application rate, MSGW can be utilized as a nutrient source for plant growth. Further long-term field studies to evaluate the environmental impact of MSGW usage in agriculture are being designed to reduce the environmental risks associated with the reuse of this underutilized wastewater in the agriculture.     

Changes in oxidative stress defense system in wheat (Triticum aestivum L.) and mung bean (Vigna radiata L.) cultivars grown with and without mineral nutrients and irradiated by supplemental ultraviolet-B

Field study was conducted to evaluate the inter- and intra-specific variations in sensitivity of two cultivars each of wheat (Triticum aestivum L. cv. HD 2329 and HUW 234) and mung bean (Vigna radiata L. cv. Malviya Jyoti and Malviya Janpriya) to supplemental levels of UV-B irradiation (sUV-B, 280–315 nm) with and without recommended levels of mineral nutrients. Results showed decrease in photosynthetic pigments and biomass of all the four cultivars due to sUV-B radiation. Antioxidative defense system was activated in all the cultivars after irradiation with sUV-B. SOD, peroxidase and total thiol contents increased, while catalase activity and ascorbic acid contents decreased under sUV-B irradiation. On the basis of biomass, UV-B sensitivity can be arranged in decreasing order as: Malviya Janpriya < Malviya Jyoti < HD 2329 < HUW 234. Application of mineral nutrients (N, P and K) showed significant positive response in all cultivars by ameliorating the negative impact of sUV-B.     

Freeze tolerance and accumulation of cryoprotectants in the enchytraeid Enchytraeus albidus (Oligochaeta) from Greenland and Europe

The freeze tolerance and accumulation of cryoprotectants was investigated in three geographically different populations of the enchytraeid Enchytraeus albidus (Oligochaeta). E. albidus is widely distributed from the high Arctic to temperate Western Europe. Our results show that E. albidus is freeze tolerant, with freeze tolerance varying extensively between Greenlandic and European populations. Two populations from sub Arctic (Nuuk) and high Arctic Greenland (Zackenberg) survived freezing at −15 °C, whereas only 30% of a German population survived this temperature. When frozen, E. albidus responded by catabolising glycogen to glucose, which likely acted as a cryoprotectant. The average glucose concentrations were similar in the three populations when worms were frozen at −2 °C, approximately 50 μg glucose mg⁻¹ tissue dry weight (DW). At −14 °C the glucose concentrations increased to between 110 and 170 μg mg⁻¹ DW in worms from Greenland. The average glycogen content of worms from Zackenberg and Nuuk were about 300 μg mg⁻¹ DW, but only 230 μg mg⁻¹ DW in worms from Germany showing that not all glycogen was catabolised during the experiment. Nuclear magnetic resonance spectrometry (NMR) was used to screen for other putative cryoprotectants. Proline, glutamine and alanine were up regulated in frozen worms at −2 °C but only in relatively small concentrations suggesting that they were of little significance for freeze survival. The present study confirms earlier reports that freeze tolerant enchytraeids, like other freeze tolerant oligochaete earthworms, accumulate high concentrations of glucose as a primary cryoprotectant.     

Performance of cabbage stem flea beetle larvae (Psylliodes chrysocephala) in brassicaceous plants and the effect of glucosinolate profiles

The cabbage stem flea beetle (CSFB), Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae), is one of the most important pests in European winter oilseed rape production. Adult beetles feed on young leaves whereas larvae mine within the petioles and stems. Larval infestation can cause significant crop damage. In this study, the host quality for CSFB of four oilseed rape (Brassica napus L.) cultivars and seven other brassicaceous species with different glucosinolate (GSL) profiles was assessed under controlled conditions. Larval instar weights and mortality were measured after 14 and 21 days of feeding in the petioles of test plants. To study the impact of GSL on the performance of larvae, the GSL contents in petioles from non-infested and infested plants were analysed before, and 21 days after, the start of larval infestation. Larval performance was not significantly different between the four cultivars of oilseed rape, but differed considerably among the other brassicaceous species tested. In comparison to the weight of larvae in the standard B. napus cv. Robust, the larval weight was higher in turnip rape (Brassica rapa L. var. silvestris) and significantly reduced in white mustard (Sinapis alba L.), oil radish (Raphanus sativa L. var. oleiformis), and cabbage (Brassica oleracea L. convar. capitata var. alba). The duration of larval development increased in white mustard and oilseed radish. The GSL profiles of the petioles showed little difference between non-infested and infested plants of oilseed rape whereas the content of aliphatic GSL increased in the infested turnip rape plants. In contrast, the aliphatic and benzenic GSL decreased in infested Indian rape (B. rapa subsp. dichotoma Roxb.). Larval weight was not correlated with the total GSL content of plants, neither before infestation nor 21 days after. Larval weight was positively correlated with progoitrin and 4-hydroxyglucobrassicin. White mustard, which provides inferior host quality for larval development, has the potential to introduce insect resistance into high-yielding oilseed rape cultivars in breeding programmes.     

Direct visualization of the lateral structure of giant vesicles composed of pseudo-binary mixtures of sulfatide,asialo-GM1 and GM1 with POPC

We compared the lateral structure of giant unilamellar vesicles (GUVs) composed of three pseudo binary mixtures of different glycosphingolipid (GSL), i.e. sulfatide, asialo-GM1 or GM1, with POPC. These sphingolipids possess similar hydrophobic residues but differ in the size and charge of their polar head group. Fluorescence microscopy experiments using LAURDAN and DiIC₁₈ show coexistence of micron sized domains in a molar fraction range that depends on the nature of the GSLs. In all cases, experiments with LAURDAN show that the membrane lateral structure resembles the coexistence of solid ordered and liquid disordered phases. Notably, the overall extent of hydration measured by LAURDAN between the solid ordered and liquid disordered membrane regions show marked similarities and are independent of the size of the GSL polar head group. In addition, the maximum amount of GSL incorporated in the POPC bilayer exhibits a strong dependence on the size of the GSL polar head group following the order sulfatide > asialo-GM1 > GM1. This observation is in full harmony with previous experiments and theoretical predictions for mixtures of these GSL with glycerophospholipids. Finally, compared with previous results reported in GUVs composed of mixtures of POPC with the sphingolipids cerebroside and ceramide, we observed distinctive curvature effects at particular molar fraction regimes in the different mixtures. This suggests a pronounced effect of these GSL on the spontaneous curvature of the bilayer. This observation may be relevant in a biological context, particularly in connection with the highly curved structures found in neural cells.     

Protocorm culture of Dendrobium candidum in balloon type bubble bioreactors

Protocorm cultures of Dendrobium candidum were established in balloon type bubble bioreactors using Murashige and Skoog (MS) medium with 0.5 mg l⁻¹ α-naphthaleneacetic acid (NAA), 2.5% (w/v) sucrose, 5:25 mM NH₄:NO₃ and 1% (v/v) banana homogenate for the production of biomass and bioactive compounds. In 3 l bioreactor containing 2 l medium, a maximum protocorm biomass (21.0 g l⁻¹ dry biomass) and also optimum quantities of total polysaccharides (389.3 mg g⁻¹ DW), coumarins (18.0 mg g⁻¹ DW), polyphenolics (11.9 mg g⁻¹ DW), and flavonoids (4.5 mg g⁻¹ DW) were achieved after 7 weeks of culture. Based on these studies, 5 and 10 l bioreactor cultures were established to harvest 80 g and 160 g dry biomass. In 10 l bioreactors, the protocorms grown were accumulated with optimal levels of polysaccharides (424.1 mg g⁻¹ DW), coumarins (15.8 mg g⁻¹ DW), polyphenols (9.03 mg g⁻¹ DW) and flavonoids (4.7 mg g⁻¹ DW). The bioreactor technology developed here will be useful for the production of important bioactive compounds from D. candidum.     

Optimization of extraction method for LC–MS based determination of phenolic acid profiles in different Impatiens species

The main aim of presented study was the comparison of various extraction methods for the quantitative and qualitative analysis (LC-ESI–MS/MS) of phenolic acids present in extracts obtained from leaves, flowers, and roots of Impatiens glandulifera. The accelerated solvent extraction (ASE) at three temperature ranges (80° C, 100° C, and 120° C), ultrasound assisted extraction (USAE) at 60° C, and traditional extraction in Soxhlet apparatus were used. Taking into account the extraction yield, and the diversity of the individual compounds, ultrasound assisted extraction proved to be the most efficient method, and it was used to determine the content of phenolic acids in leaves of four other Impatiens species, including I. balsamina, I. noli-tangere, I. parviflora, and I. walleriana. Eleven phenolic acids were identified in all examined species. These were protocatechuic, gentisic, 4- hydroxybenzoic, vanillic, trans-caffeic, syringic, trans-p-coumaric, trans- and cis-ferulic, salicylic, and 3-hydroxycinnamic acids. In the extract from the leaves of I. balsamina and I. walleriana, gallic and cis-p-coumaric acids were found additionally. The most abundant compounds in all examined extracts were protocatechuic and 3-hydroxycinnamic acids. The latest acid was found in the highest yield in I. noli-tangere (266.12 μg/g DW). In the leaves of I. glandulifera a great amount of 4-hydroxybenzoic (41.44 μg/g DW), vanillic (61.50 μg/g DW), and trans-p-coumaric (58.42 μg/g DW) acids was also observed. Our results indicate that protocatechuic, 4-hydroxybenzoic, vanillic, trans-p-coumaric, trans-ferulic, and 3-hydroxycinnamic acids were most characteristic of Impatiens species.Additionally, various phenolic-rich extracts from leaves, flowers, and roots of Impatiens glandulifera were tested for antioxidant activity. The highest antiradical activity was detected for roots using Soxhlet extraction (EC50 = 0.055 mg [DE/ml]).The study demonstrated that members of the genus Impatiens, and in particular Impatiens glandulifera, and Impatiens noli-tangere, contain significant amounts of phenolic acids. In addition, extracts from various parts of I. glandulifera could be interesting as novel sources of natural antioxidants.     

Evaluation of in vitro free radical scavenging potential of Streptomyces sp. AM-S1 culture filtrate

The present study was carried out to determine the free radical scavenging potential of culture filtrate of Streptomyces sp. AM-S1. Antioxidant activity of culture filtrate, lyophilized culture filtrate and ethyl acetate extract of Streptomyces sp. AM-S1 was determined by various in vitro assays such as ferric reducing power assay, phosphomolybdenum reduction, DPPH and ABTS radical scavenging activities. The results revealed that the culture filtrate of Streptomyces sp. AM-S1 effectively scavenged DPPH (IC₅₀ 90.2 μl/ml) and ABTS (IC₅₀ 13.2 μl/ml) radicals in a concentration dependent manner. In all the assays, ethyl acetate extract registered higher antioxidant activity when compared with the lyophilized culture filtrate (LCF). In addition, ethyl acetate extract (1123.4 μmole Fe(II)/mg extract) exhibited higher ferric reducing activity than the standard BHA (814.4 μmole Fe(II)/mg extract). Further works are needed on the isolation and identification of antioxidant molecules from the ethyl acetate extract of Streptomyces sp. AM-S1 culture filtrate.     

Lead,zinc, cadmium hyperaccumulation and growth stimulation in Arabis paniculata Franch

Metal hyperaccumulation is of great interest in recent years because of its potential application for phytoremediation of heavy metal contaminated soils. In this study, a field survey and a hydroponic experiment were conducted to study the accumulation characteristics of lead (Pb), zinc (Zn) and cadmium (Cd) in Arabis paniculata Franch., which was found in Yunnan Province, China. The field survey showed that the wild population of A. paniculata was hyper-tolerant to extremely high concentrations of Pb, Zn and Cd, and could accumulate in shoots an average level of 2300 mg kg^?1 dry weight (DW) Pb, 20,800 mg kg^?1 Zn and 434 mg kg^?1 Cd, with their translocation factors (TFs) all above one. Under the hydroponic culture, stimulatory effects of Pb, Zn and Cd on shoot dry biomass were noted from 24 to 193 μM Pb, 9 to 178 μM Cd and all Zn supply levels in nutrient solution, while the effects were not obvious in the roots. Chlorophyll concentrations in Pb, Zn and Cd treatments showed an inverted U-shaped pattern, consistent with the change of plant biomass. Pb, Zn and Cd concentrations in the shoots and roots increased sharply with increasing Pb, Zn and Cd supply levels. They reached > 1000 mg kg^?1 Pb, 10,000 mg kg^?1 Zn and 100 mg kg^?1 Cd DW in the 24 μM Pb, 1223 μM Zn and 9 μM Cd treatment, respectively, in which the plants grew healthy and did not show any symptoms of phytotoxicity. The TFs of Zn were basically higher than one and the amount of Zn taken by shoots ranged from 78.7 to 90.4% of the total Zn. However, the TFs of Pb and Cd were well below one, and 55.0–67.5% of total Pb and 57.8–83.5% of total Cd was accumulated in the shoots. These results indicate that A. paniculata has a strong ability to tolerate and hyperaccumulate Pb, Zn and Cd. Meanwhile, suitable levels of Pb, Zn and Cd could stimulate the biomass production and chlorophyll concentrations of A. paniculata. Thus, it provides a new plant material for understanding the mechanisms of stimulatory effect and co-hyperaccumulation of multiple heavy metals.     

A reassessment of the prevalent organic solutes constitutively accumulated and potentially involved in osmotic adjustment in pear leaves

In higher plants, osmotic adjustment at the various levels of plant organization is partly achieved through accumulation of a range of osmolytes especially LMW organic solutes often termed as osmotic solutes. A metabolite profiling of crude extracts of mature pear leaves of a range of 8 Pyrus genotypes was performed using current HPLC, UPLC and ¹H NMR spectroscopy techniques in order to identify such putative compounds. Using as variables the concentrations of 45 identified substances and those of a restricted number of unknowns, all belonging to LMW carbohydrates, polyols, organic acids, amino acids and phenolics on the one hand, and the varieties investigated as individuals on the other, we generated a set of data analyzed further by PCA. Those varieties were discriminated into three clusters respectively comprised of the four Asian varieties, the European variety Williams grafted onto 4 different rootstocks, and the two other European varieties Conference and Angelys. These metabolic phenotypes were shown to rely more on scion genotypes than on rootstocks. High to very high amounts of sorbitol (average content of 363 μmol g^?1 DW) associated with low amounts of mannitol and myo-inositol were found in all genotypes as well as in a local ecotype of P. communis where the hexitol accounted for 7.3% DW. Sorbitol actually represented up to 30-40% of the total osmotically active organic solutes accumulated in the set of pear leaves investigated, and it was shown to be significantly more abundant in the variety Williams than in Asian ones (p < 0.01). In contrast, the other well-known compatible solute glycine betaine, barely detectable using ¹H NMR spectroscopy or HPLC, occurred in leaves of all pear varieties at weak levels lower than 2 μmol g^?1 DW which suggested a minor role in osmotic adjustment. Its amount does not seem to be altered in response to an osmotic upshift applied to detached leaves or to depend on exogenously supplied ABA. For non-sustantiated reasons, these results are in contrast with those showing elsewhere very high accumulation of GB in the Asian genotype Su li. In this study mature leaves of this genotype collected from the same tree in July 2007 and July 2006 were shown to contain respectively 0.59 ± 0.04 and 0.85 ± 0.04 μmol g^?1 DW. Other abundant organic substances like arbutine, quinic acid, malic acid, sucrose as well as chlorogenic acid and other quinic acid adducts, might also behave as osmotically active substances. In addition to arbutine, its derivative hydroquinone, chlorogenic acid and structurally related substances might be involved in protective functions against secondary oxidative stresses induced by abiotic and biotic stresses encountered during the growing season.     

Studies on the accumulation of phenolic acids and flavonoids in different in vitro culture systems of Schisandra chinensis (Turcz.) Baill. using a DAD-HPLC method

Different in vitro culture systems of the East-Asian origin medicinal plant species − Schisandra chinensis, were tested in order to investigate their potential for the accumulation of two groups of phenolic compounds. In vitro cultures were maintained on the Murashige and Skoog (MS) medium supplemented with 3 mg/l BA and 1 mg/l NAA in an agar system (30- and 60-day growth cycles), and also in two different liquid systems: stationary and agitated. Stationary liquid cultures were grown in batch (30- and 60-day growth cycles) and fed-batch modes. Of the twenty compounds, seven free phenolic acids and of the eleven compounds, five flavonoids were quantified in methanolic extracts from lyophilized biomass and in the growth media using the RP-HPLC-DAD method. For comparison purposes, phytochemical analyses of leaf and fruit extracts from the parent plant were also conducted. The estimated compounds were not detected in the growth media. The highest total amounts of phenolic acids (71.48 mg/100 g DW) and flavonoids (29.36 mg/100 g DW) were found in extracts from the biomass of agar cultures harvested after 30 days of cultivation. The main metabolites in all the tested systems were: protocatechuic acid (max. 35.69 mg/100 g DW), chlorogenic acid (max. 13.05 mg/100 g DW), and quercitrin (max. 27.43 mg/100 g DW).