Inoculation with arbuscular mycorrhizal fungi improves the nutritional value of tomatoes.

Arbuscular mycorrhizal (AM) fungi can affect many different micronutrients and macronutrients in plants and also influence host volatile compound synthesis. Their effect on the edible portions of plants is less clear. Two separate studies were performed to investigate whether inoculation by AM fungi (Rhizophagus irregularis, Funneliformis mosseae, or both) can affect the food quality of tomato fruits, in particular common minerals, antioxidants, carotenoids, a suite of vitamins, and flavor compounds (sugars, titratable acids, volatile compounds). It was found that AM fungal inoculation increased the nutrient quality of tomato fruits for most nutrients except vitamins. Fruit mineral concentration increased with inoculation (particularly N, P, and Cu). Similarly, inoculated plants had fruit with higher antioxidant capacity and more carotenoids. Furthermore, five volatile compounds were significantly higher in AM plants compared with non-AM controls. Taken together, these results show that AM fungi represent a promising resource for improving both sustainable food production and human nutritional needs.

UV-B irradiation changes specifically the secondary metabolite profile in broccoli sprouts: induced signaling overlaps with defense response to biotic stressors.

Only a few environmental factors have such a pronounced effect on plant growth and development as ultraviolet light (UV). Concerns have arisen due to increased UV-B radiation reaching the Earth's surface as a result of stratospheric ozone depletion. Ecologically relevant low to moderate UV-B doses (0.3-1 kJ m(-2) d(-1)) were applied to sprouts of the important vegetable crop Brassica oleracea var. italica (broccoli), and eco-physiological responses such as accumulation of non-volatile secondary metabolites were related to transcriptional responses with Agilent One-Color Gene Expression Microarray analysis using the 2×204 k format Brassica microarray. UV-B radiation effects have usually been linked to increases in phenolic compounds. As expected, the flavonoids kaempferol and quercetin accumulated in broccoli sprouts (the aerial part of the seedlings) 24 h after UV-B treatment. A new finding is the specific UV-B-mediated induction of glucosinolates (GS), especially of 4-methylsulfinylbutyl GS and 4-methoxy-indol-3-ylmethyl GS, while carotenoids and Chl levels remained unaffected. Accumulation of defensive GS metabolites was accompanied by increased expression of genes associated with salicylate and jasmonic acid signaling defense pathways and up-regulation of genes responsive to fungal and bacterial pathogens. Concomitantly, plant pre-exposure to moderate UV-B doses had negative effects on the performance of the caterpillar Pieris brassicae (L.) and on the population growth of the aphid Myzus persicae (Sulzer). Moreover, insect-specific induction of GS in broccoli sprouts was affected by UV-B pre-treatment.

Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure.

The aim of this study was to investigate the modifying influence of moderate ultraviolet-B (UV-B) radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during pre-harvest using kale, a leafy Brassica species with a wide spectrum of different non-acylated and acylated flavonol glycosides. Juvenile kale plants were treated with short-term (1 day), moderate UV-B radiation [0.22-0.88 kJ m⁻² day⁻¹ biologically effective UV-B (UV-B(BE))]. Twenty compounds were quantified, revealing a structure-specific response of flavonol glycosides and hydroxycinnamic acid derivatives to UV-B radiation. A dose- and structure-dependent response of the investigated phenolic compounds to additional UV-B radiation was found. The investigated quercetin glycosides decreased under UV-B; for kaempferol glycosides, however, the amount of sugar moieties and the flavonol glycoside hydoxycinnamic acid residue influenced the response to UV-B. Monoacylated kaempferol tetraglucosides decreased in the investigated UV-B range, whereas the monoacylated kaempferol diglucosides increased strongly with doses of 0.88 kJ m⁻² day⁻¹ UV-B(BE) . The UV-B-induced increase in monoacylated kaempferol triglucosides was dependent on the acylation pattern. Furthermore, the hydroxycinnamic acid glycosides disinapoyl-gentiobiose and sinapoyl-feruloyl-gentiobiose were enhanced in a dose-dependent manner under UV-B. While UV-B radiation treatments often focus on flavonol aglycones or total flavonols, our investigations were extended to structurally different non-acylated and acylated glycosides of quercetin and kaempferol.

Isothiocyanate-containing mustard protects human cells against genotoxins in vitro and in vivo.

BACKGROUND: Human intervention trials in which cytogenetic biomarkers are used as intermediate endpoints in carcinogenesis are implicitly required to support the assumption of chemo-preventive efficacy. METHODS: To evaluate the genotoxic and anti-genotoxic properties of defined isothiocyanate-containing mustard, we first used a human liver cell-line and then conducted a controlled pilot human intervention trial. Blood from volunteers served as surrogate tissue for time-kinetic analysis of the chemo-preventive effect of mustard consumption. RESULTS: Mustard extracts displayed significant anti-genotoxicity against benzo(a)pyrene in human HepG2 hepatoma cells. At high concentrations, the extracts induced genotoxicity by themselves without compromising cell viability. The protective effect of mustard supplementation against DNA damage induced ex vivo was detected in blood of volunteers within 12h after the start of the intervention, and increased over time. No genotoxicity was induced in human peripheral mononuclear blood cells by mustard intake over the whole period of the study. Also, liver parameters remained within the normal range at all times. Although no change in total plasma GST activity was detected, plasma alpha-GST levels increased over time, peaking at 48 h. CONCLUSIONS: The results suggest the capacity of small amounts of isothiocyanate-containing food to protect cells from DNA damage, even with short-term application.

Effects of dark septate endophytes on tomato plant performance.

Non-mycorrhizal fungal root endophytes can be found in all natural and cultivated ecosystems, but little is known about their impact on plant performance. The impact of three mitosporic dark septate endophytes (DSE48, DSE49 and Leptodontidium orchidicola) on tomato plant characteristics was studied. Their effects on root and shoot growth, their influence on fruit yield and fruit quality parameters and their ability to diminish the impact of the pathogen Verticillium dahliae were investigated. While shoot biomass of young plants was enhanced between 10% and 20% by the endophytes DSE48 and L. orchidicola in one of two experiments and by DSE49 in both experiments, vegetative growth parameters of 24-week-old plants were not affected except a reproducible increase of root diameter by the isolate DSE49. Concerning fruit yield and quality, L. orchidicola could double the biomass of tomatoes and increased glucose content by 17%, but this was dependent on date of harvest and on root colonisation density. Additionally, the endophytes DSE49 and L. orchidicola decreased the negative effect of V. dahliae on tomato, but only at a low dosage of the pathogen. This indicates that the three dark septate endophytes can have a significant impact on tomato characters, but that the effects are only obvious at early stages of vegetative and generative development and currently too inconsistent to recommend the application of these DSEs in horticultural practice.

Identification of complex, naturally occurring flavonoid glycosides in kale (Brassica oleracea var. sabellica) by high-performance liquid chromatography diode-array detection/electrospray ionization multi-stage mass spectrometry.

Kale is a member of the Brassicaceae family and has a complex profile of flavonoid glycosides. Therefore, kale is a suitable matrix to discuss in a comprehensive study the different fragmentation patterns of flavonoid glycosides. The wide variety of glycosylation and acylation patterns determines the health-promoting effects of these glycosides. The aim of this study is to investigate the naturally occurring flavonoids in kale. A total of 71 flavonoid glycosides of quercetin, kaempferol and isorhamnetin were identified using a high-performance liquid chromatography diode-array detection/electrospray ionization multi-stage mass spectrometry (HPLC-DAD/ESI-MS(n)) method. Of these 71 flavonol glycosides, 27 were non-acylated, 30 were monoacylated and 14 were diacylated. Non-acylated flavonol glycosides were present as mono-, di-, tri- and tetraglycosides. This is the first time that the occurrence of four different fragmentation patterns of non-acylated flavonol triglycosides has been reported in one matrix simultaneously. In addition, 44 flavonol glycosides were acylated with p-coumaric, caffeic, ferulic, hydroxyferulic or sinapic acid. While monoacylated glycosides existed as di-, tri- and tetraglycosides, diacylated glycosides occurred as tetra- and pentaglycosides. To the best of our knowledge, 28 compounds in kale are reported here for the first time. These include three acylated isorhamnetin glycosides (isorhamnetin-3-O-sinapoyl-sophoroside-7-O-D-glucoside, isorhamnetin-3-O-feruloyl-sophoroside-7-O-diglucoside and isorhamnetin-3-O-disinapoyl-triglucoside-7-O-diglucoside) and seven non-acylated isorhamnetin glycosides.

Flavonoid, Nitrate and Glucosinolate Concentrations in Brassica Species Are Differentially Affected by Photosynthetically Active Radiation, Phosphate and Phosphite.

We evaluated the effects of phosphate (Pi-deficiency: 0.1 mM; Pi-sufficiency: 0.5 mM), phosphite (low-Phi: 0.1 mM; medium-Phi: 0.5 mM; and high-Phi: 2.5 mM), and two mean daily photosynthetically active radiations (lower PAR: 22.2 mol ⋅ m-2 ⋅ d-1; higher PAR: 29.7 mol ⋅ m-2 ⋅ d-1), as well as their interactions, on flavonoid, nitrate and glucosinolate (GL) concentrations and growth characteristics in hydroponically grown Brassica campestris cv. Mibuna Early and Brassica juncea cv. Red Giant. As expected, higher PAR increased dry matter and contrariwise decreased number of leaves but only in B. campestris. Total flavonoid and individual flavonoid compounds increased with the higher PAR value in B. campestris. Pi-sufficiency resulted in a lower quercetin concentration in both species, the isorhamnetin and total flavonoid concentrations in B. campestris, and the cyanidin concentration in B. juncea, in comparison to Pi-deficiency. Similarly, Pi-sufficient plants exhibited lower GL concentration, especially alkyl-GLs in B. campestris and alkenyl-GLs and an aryl-GL in B. juncea. Pi did not affect the nitrate concentration in either species, and nor did Phi influence the flavonoid concentrations in either species. In B. campestris, medium Phi (0.5 mM) increased the 1-methoxyindol-3-ylmethyl GL concentration by 28.3%, as compared to that observed at low Phi. In B. juncea, high Phi level increased the but-3-enyl-GL concentration by 18.9%, in comparison to values recorded at medium Phi. B. campestris plants exposed to higher PAR increased total flavonoids concentration. In both Brassica species, higher PAR stimulated the alkyl-, alkenyl-, and indole-GLs. The interaction of lower PAR and increasing Phi significantly decreased flavonoid concentration in B. juncea, whereas increasing Phi at higher PAR increased such concentration in this species. The same combination reduced the concentration of 2-phenylethyl- and indol-3-ylmethyl-GL in B. juncea. The highest indol-3-ylmethyl-GL concentration was observed when Pi was deficient combined with medium Phi in B. juncea. Thus, PAR, Pi and Phi may modulate flavonoid, GL and nitrate concentrations in Brassica species, which may be a useful tool to improve the nutraceutical quality of these leafy vegetables if properly managed.

Identification of desulphoglucosinolates in Brassicaceae by LC/MS/MS: comparison of ESI and atmospheric pressure chemical ionisation-MS.

In order to develop a sensitive method for the detection of desulphoglucosinolates by HPLC-MS, the two most common interfaces for HPLC-MS, atmospheric pressure chemical ionisation (APCI) and ESI, were compared. While working with the APCI-interface the evaporation temperature and corona amperage were optimised. In doing so 300 degrees C and 6 muA proved to be most suitable for aliphatic and indole desulphoglucosinolates. The use of formic acid instead of water in the eluent in HPLC-ESI-MS measurements increased the sensitivity for the indole desulphoglucosinolates in the presence of 1 mM formic acid, while the sensitivity for the aliphatic desulphoglucosinolate desulphoglucoraphanin was substantially increased by the presence of 5 mM formic acid. Using an Agilent ion trap, two optimisation procedures for the MS parameters, smart and expert mode, were available. In smart mode the software optimises several parameters automatically, which is much more time efficient than expert mode, in which the optimisation is done manually. It turned out that ESI-MS is most sensitive in smart mode, while for APCI-MS a higher sensitivity could be gained using the expert mode. Comparing both interfaces, APCI-MS was more sensitive than ESI-MS. However, no additional information, in terms of structure determination, was obtained by APCI-MS.

Glucosinolate concentration in turnip (Brassica rapa ssp. rapifera L.) roots as affected by nitrogen and sulfur supply.

Three greenhouse pot experiments were conducted with four different nitrogen (N) treatments (80, 160, 240, and 320 kg ha (-1)) in combination with three sulfur (S) treatments (10, 20, and 60 kg ha (-1)) to study the effects of combined N and S supply on glucosinolate concentration and composition in turnip roots. Total glucosinolate concentration varied widely from 9.7 (N 320S 10) to 91.6 (N 160S 60) mg (100 g) (-1) root fresh weight (FW) and individual glucosinolate concentrations were increased with increasing S supply regardless of the N treatment, whereas enhanced N supply (160 - 320 N ha (-1)) at the high S level (60 kg ha (-1)) did not affect total glucosinolate concentration. In contrast, assumingly attributed to the individual glucosinolate biosynthesis concentration of N-containing tryptophan-derived indole glucosinolate was highest with increased N supply, whereas S-containing methionine-derived aromatic and aliphatic glucosinolates decreased with increasing N supply combined at low S level (10-20 kg ha (-1)).

Long-term response of tomato plants to changing nutrient concentration in the root environment-the role of proline as an indicator of sensory fruit quality.

The aim of the trial was to investigate the time course of changes in content of proline and organic compounds affecting sensory quality of ripe red tomatoes after nutrient concentration had been changed. Tomato (Lycopersicon esculentum Mill. cv. Counter) plants were grown in nutrient solutions containing equal nutrient ratios at either low or high concentration (N1=standard solution; N2=5.5 times the standard concentration). Immediately after first harvest of ripe tomatoes, half of the plants of each treatment were transferred to nutrient solutions of higher (from N1 to N2) or lower (from N2 to N1) nutrient concentration. Proline content in leaves of plants transferred to higher or lower nutrient concentration adjusted to control levels (N2 and N1, respectively) within 2 weeks. Growing and ripe fruit reached the corresponding control levels within the same time or 1-5 weeks later. Similar time courses were observed for sugar concentration and titratable acidity in fruit. Apart from leaves, proline content of young growing fruit also increased with increasing radiation intensity at high nutrient concentration. However, in ripe fruit, proline content increased only with low to moderate radiation intensity and decreased when a certain stress level was exceeded. Similar results were found for osmolality and sugar concentration of ripe fruit, while titratable acidity remained rather unaffected by radiation. The role of proline as an indicator of sensory fruit quality is discussed.

Glucosinolates in mixed-packaged mini broccoli and mini cauliflower under modified atmosphere.

Contents of total and individual glucosinolates of mini broccoli cv. Milady and mini cauliflower cv. Clarke were assessed to determine the effect of modified atmosphere packaging on postharvest glucosinolate dynamics of mixed mini Brassica vegetables. Therefore, mixed-packaged mini broccoli and mini cauliflower stored in food trays sealed with two different microperforated biaxial-oriented polypropylene films for up to 7 days at 8 degrees C were analyzed. The results indicate that modified atmosphere at 8% O2 + 14% CO2 was a suitable gaseous combination to maintain aliphatic and indole glucosinolates in mini broccoli for 7 days after an initial decrease at 4 days. In contrast, modified atmosphere at 1% O2 + 21% CO2 resulted in the best retention of indole glucosinolates of mini cauliflower for 7 days and also of aliphatic glucosinolates after an initial decrease at 4 days. Thus, to maintain glucosinolates and external appearance and to prevent off-odor, mini broccoli and mini cauliflower should be packed separately in suitable altered gas composition.

Influence of Light and Temperature on Gene Expression Leading to Accumulation of Specific Flavonol Glycosides and Hydroxycinnamic Acid Derivatives in Kale (Brassica oleracea var. sabellica).

Light intensity and temperature are very important signals for the regulation of plant growth and development. Plants subjected to less favorable light or temperature conditions often respond with accumulation of secondary metabolites. Some of these metabolites have been identified as bioactive compounds, considered to exert positive effects on human health when consumed regularly. In order to test a typical range of growth parameters for the winter crop Brassica oleracea var. sabellica, plants were grown either at 400 µmol m(-2) s(-1) or 100 µmol m(-2) s(-1) at 10°C, or at 400 µmol m(-2) s(-1) with 5 or 15°C. The higher light intensity overall increased flavonol content of leaves, favoring the main quercetin glycosides, a caffeic acid monoacylated kaempferol triglycoside, and disinapoyl-gentiobiose. The higher temperature mainly increased the hydroxycinnamic acid derivative disinapoyl-gentiobiose, while at lower temperature synthesis is in favor of very complex sinapic acid acylated flavonol tetraglycosides such as kaempferol-3-O-sinapoyl-sophoroside-7-O-diglucoside. A global analysis of light and temperature dependent alterations of gene expression in B. oleracea var. sabellica leaves was performed with the most comprehensive Brassica microarray. When compared to the light experiment much less genes were differentially expressed in kale leaves grown at 5 or 15°C. A structured evaluation of differentially expressed genes revealed the expected enrichment in the functional categories of e.g. protein degradation at different light intensities or phytohormone metabolism at different temperature. Genes of the secondary metabolism namely phenylpropanoids are significantly enriched with both treatments. Thus, the genome of B. oleracea was screened for predicted genes putatively involved in the biosynthesis of flavonoids and hydroxycinnamic acid derivatives. All identified B. oleracea genes were analyzed for their most specific 60-mer oligonucleotides present on the 2 × 105 K format Brassica microarray. Expression differences were correlated to the structure-dependent response of flavonoid glycosides and hydroxycinnamic acid derivatives to alterations in either light or temperature. The altered metabolite accumulation was mainly reflected on gene expression level of core biosynthetic pathway genes and gave further hints to an isoform specific functional specialization.

Nitrogen Limited Red and Green Leaf Lettuce Accumulate Flavonoid Glycosides, Caffeic Acid Derivatives, and Sucrose while Losing Chlorophylls, Β-Carotene and Xanthophylls.

Reduction of nitrogen application in crop production is desirable for ecological and health-related reasons. Interestingly, nitrogen deficiency can lead to enhanced concentrations of polyphenols in plants. The reason for this is still under discussion. The plants' response to low nitrogen concentration can interact with other factors, for example radiation intensity. We cultivated red and green leaf lettuce hydroponically in a Mediterranean greenhouse, supplying three different levels of nitrogen (12 mM, 3 mM, 0.75 mM), either in full or reduced (-50%) radiation intensity. In both red and green lettuce, we found clear effects of the nitrogen treatments on growth characteristics, phenolic and photosynthetic compounds, nitrogen, nitrate and carbon concentration of the plants. Interestingly, the concentrations of all main flavonoid glycosides, caffeic acid derivatives, and sucrose increased with decreasing nitrogen concentration, whereas those of chlorophylls, ß-carotene, neoxanthin, lactucaxanthin, all trans- and cis-violaxanthin decreased. The constitutive concentrations of polyphenols were lower in the green cultivar, but their relative increase was more pronounced than in the red cultivar. The constitutive concentrations of chlorophylls, ß-carotene, neoxanthin, all trans- and cis-violaxanthin were similar in red and green lettuce and with decreasing nitrogen concentration they declined to a similar extent in both cultivars. We only detected little influence of the radiation treatments, e.g. on anthocyanin concentration, and hardly any interaction between radiation and nitrogen concentration. Our results imply a greater physiological plasticity of green compared to the red lettuce regarding its phenolic compounds. They support the photoprotection theory regarding anthocyanins as well as the theory that the deamination activity of phenylalanine ammonia-lyase drives phenylpropanoid synthesis.

Structural investigations of flavonol glycosides from sea buckthorn (Hippophaë rhamnoides) pomace by NMR spectroscopy and HPLC-ESI-MS(n).

Four flavonol glycosides were isolated from an extract of sea buckthorn pomace (Hippophaë rhamnoides) by Sephadex LH-20 gel chromatography and semipreparative HPLC. Their structures were elucidated by hydrolysis studies, ESI-MS(n), UV, and (1)H and (13)C NMR spectroscopy. The occurrence of the major flavonol glycoside kaempferol 3-O-beta-sophoroside-7-O-alpha-rhamnoside in sea buckthorn is described here for the first time. A further 21 flavonol glycosides of Sephadex LH-20 fractions of sea buckthorn pomace were characterized by HPLC-DAD-ESI-MS. The characteristic MS-MS and MS(3) fragmentation pattern of flavonol glycosides previously identified in sea buckthorn juice and of flavonol glycosides identified by NMR spectroscopy gave valuable indications for their identification. The results demonstrate that loss of the sugar moiety from C-7 of the aglycon is more favored than fission of the glycosidic linkage at the C-3 position. Thus, most of the compounds identified were 7-rhamnosides of isorhamnetin, kaempferol, and quercetin, which exhibit different substitution patterns at the C-3 position, mainly glucosides, rutinosides, and sophorosides. In addition, numerous flavonol glycosides were detected lacking a sugar moiety at C-7. Finally, eight flavonol derivatives were identified that are acylated by hydroxybenzoic or hydoxycinnamic acids.

Cool-cultivated red leaf lettuce accumulates cyanidin-3-O-(6″-O-malonyl)-glucoside and caffeoylmalic acid.

Cultivating lettuce in greenhouses at low temperatures improves its CO2-balance and may increase its content of flavonoid glycosides and phenolic acids. We cultivated 5weeks old red leaf lettuce seedlings at 20/15°C (day/night) or 12/7°C until plants reached comparable growth stages: small heads were harvested after 13 (warm) and 26 (cool)days, while mature heads were harvested after 26 (warm) or 52 (cool)days. Additionally, some plants were cultivated first cool then warm and vice versa (39days). Cool-cultivated small heads had higher concentrations of cyanidin-3-O-(6″-O-malonyl)-glucoside and caffeoylmalic acid than warm-cultivated ones but we detected no differences concerning quercetin and luteolin glycosides or di-O-caffeoyltartaric and 5-O-caffeoylquinic acid. Regarding mature heads, there were only differences concerning cyanidin-3-O-(6″-O-malonyl)-glucoside. We therefore suggest that only cyanidin-3-O-(6″-O-malonyl)-glucoside was truly responsive to temperatures alone. Previously reported contrasting effects may rather be due to comparison of different growth stages or interactive effects with radiation.

Unlike quercetin glycosides, cyanidin glycoside in red leaf lettuce responds more sensitively to increasing low radiation intensity before than after head formation has started.

This study investigated the effect of low-level photosynthetic photon flux density (PPFD; 43-230 µmol m(-2) s(-1)) on the major phenolic compounds of red leaf lettuce in three growth stages, before, during, and after head formation, using HPLC-DAD-ESI-MS(2) and evaluating via multiple regression analysis. Generally, the light-related increase of flavonoid glycosides was structure and growth stage-dependent. In detail, an interaction was detected between plant age and PPFD regarding cyanidin-3-O-(6"-O-malonyl)-glucoside concentration: the increase was strongest before head formation. The relationship between PPFD and quercetin-3-O-(6"-O-malonyl)-glucoside concentration was linear, whereas the increase of quercetin-3-O-glucoside and -3-O-glucuronide concentrations abated with increasing PPFD. Independent of growth stage, the caffeic acid derivatives concentration was not related to PPFD. All major phenolic compounds decreased with plant age. These results show the differential regulation of cyanidin, quercetin, and caffeic acid derivatives in lettuce, although closely connected biosynthetically, and emphasize the importance of ontogeny in the study of plant physiology.

Interaction of moderate UV-B exposure and temperature on the formation of structurally different flavonol glycosides and hydroxycinnamic acid derivatives in kale (Brassica oleracea var. sabellica).

Kale has a high number of structurally different flavonol glycosides and hydroxycinnamic acid derivatives. In this study we investigated the interaction of moderate UV-B radiation and temperature on these compounds. Kale plants were grown at daily mean temperatures of 5 or 15 °C and were exposed to five subsequent daily doses (each 0.25 kJ m(-2) d(-1)) of moderate UV-B radiation at 1 d intervals. Of 20 phenolic compounds, 11 were influenced by an interaction of UV-B radiation and temperature, e.g., monoacylated quercetin glycosides. Concomitantly, enhanced mRNA expression of flavonol 3'- hydroxylase showed an interaction of UV-B and temperature, highest at 0.75 kJ m(-2) and 15 °C. Kaempferol glycosides responded diversely and dependent on, e.g., the hydroxycinnamic acid residue. Compounds containing a catechol structure seem to be favored in the response to UV-B. Taken together, subsequent exposure to moderate UV-B radiation is a successful tool for enhancing the flavonoid profile of plants, and temperature should be considered.

Topsoil drying combined with increased sulfur supply leads to enhanced aliphatic glucosinolates in Brassica juncea leaves and roots.

The decrease of water availability is leading to an urgent demand to reduce the plants' water supply. This study evaluates the effect of topsoil drying, combined with varying sulfur (S) supply on glucosinolates in Brassica juncea in order to reveal whether a partial root drying may already lead to a drought-induced glucosinolate increase promoted by an enhanced S supply. Without decreasing biomass, topsoil drying initiated an increase in aliphatic glucosinolates in leaves and in topsoil dried roots supported by increased S supply. Simultaneously, abscisic acid was determined, particularly in dehydrated roots, associated with an increased abscisic acid concentration in leaves under topsoil drying. This indicates that the dehydrated roots were the direct interface for the plants' stress response and that the drought-induced accumulation of aliphatic glucosinolates is related to abscisic acid formation. Indole and aromatic glucosinolates decreased, suggesting that these glucosinolates are less involved in the plants' response to drought.

Genotypic variation of the glucosinolate profile in pak choi (Brassica rapa ssp. chinensis).

Thirteen different pak choi (Brassica rapa ssp. chinensis) cultivars were characterized regarding their glucosinolate profile analyzed by HPLC-DAD-MS. The identified glucosinolates were subjected to principal component analysis, and three distinct groups of pak choi sprouts were identified. Group differences were marked mainly by variations in the aliphatic glucosinolate profile such as differing levels of 3-butenyl glucosinolate and 2-hydroxy-3-butenyl glucosinolate as well as by their varying proportional ratios. In addition, the three groups of pak choi sprouts varied by the presence or absence of 2-hydroxy-4-pentenyl glucosinolate and in level and composition of butyl glucosinolates. This classification is reflected by relative mRNA expression level of 2-oxoacid-dependent dioxygenase. As in sprouts, the major glucosinolates in mature leaves were found to be the aliphatic glucosinolates. However, unlike in sprouts, an additional aliphatic glucosinolate, 5-methylsulfinylpentyl glucosinolate, was detected as characteristic ontogenetic variation in mature leaves in 12 of the 13 pak choi cultivars analyzed.

Temporary reduction of radiation does not permanently reduce flavonoid glycosides and phenolic acids in red lettuce.

Applying transparent daytime screens in greenhouses in cool seasons reduces the amount of energy needed for heating, but also the solar radiation available for crops. This can reduce yield and product quality of leafy vegetables because of constrained photosynthesis and altered biosynthesis. To study this, we cultivated five-week old red leaf lettuce (Lactuca sativa L.) for four weeks in growth chambers under a photosynthetic photon flux density (PPFD) of 225 and 410 µmol m(-2) s(-1), respectively. Some plants were exchanged between radiation intensities after two weeks. We investigated the concentration of five flavonoid glycosides, three caffeic acid derivatives, reducing sugars as well as plant growth. Remarkably, no significant influence of radiation intensity on the concentration of phenolic acids or anthocyanin glycosides was observed. In contrast, quercetin and luteolin glycoside concentration was between 14 and 34% lower in plants growing under lower compared to higher PPFD. Already after two weeks of cultivation, plants grown under lower PPFD contained less quercetin and luteolin glycosides but they completely compensated if subsequently transferred to higher PPFD until harvest. Hence, marketable lettuce heads which experienced temporary shading followed by an unshaded phase did not contain lower concentrations of flavonoid glycosides or phenolic acids. Also, there was no reduction of head mass in this variant. Our results suggest that saving energy in early growth stages is feasible without losses in yield or health promoting phenolic substances. In addition, there was a close correlation between the concentration of reducing sugars and some flavonoid glycosides, indicating a close metabolic connection between their biosynthesis and the availability of carbohydrates.