Effect of CO(2) enrichment on synthesis of some primary and secondary metabolites in ginger (Zingiber officinale Roscoe)

Chitosan nanoparticles upregulate C and N metabolism in soybean plants grown under elevated levels of atmospheric carbon dioxide

Despite the wide utilization of chitosan nanoparticles (CSNPs) as a promising approach for sustainable agriculture, their efficiency under elevated CO2 (eCO2), has not been evaluated. The interactive effects of CSNPs and eCO2 were evaluated on the growth and C and N metabolism of soybean plants. Plants were treated with CSNPs and grown under ambient CO2 (410 ppm, aCO2) or eCO2 (645 ppm). Regardless of CO2 level, CSNPs improved the net photosynthetic rate. CSNPs aggravated the effect of eCO2 treatment on the levels of non-structural carbohydrates (i.e., glucose, fructose, sucrose, and starch), especially in shoots, which was inconsistence with the upregulation of carbohydrates metabolizing enzymes. Being the most pivotal energetic and signaling organic compounds in higher plants, the synergistic action of CSNPs and eCO2 on the accumulation of soluble sugars upregulated the N metabolism as indicated by induced activities of nitrate reductase, arginase, glutamate dehydrogenase, glutamine synthetase, and glutamine oxoglutarate aminotransferase which was manifested finally as increased shoot and root total nitrogen content as well as proline and aspartate in roots. At the hormonal level, the coexistence of eCO2 with CSNPs further supports their positive impact on the contents of IAA and, to a lesser extent, GAs. The present data prove that the biofertilization capacity of CSNPs is even more potent under futuristic eCO2 levels and could even further improve the growth and resilience of plants.

Effect of salicylic acid elicitor on antioxidant potential and chemical composition of in vitro raised plants of Berberis asiatica Roxb. ex DC

The present study for the first time investigated the effects of Salicylic acid (SA) (50, 100 and 200 mg/L) on in vitro growth and antioxidant capacity of Berberis asiatica. SA significantly enhanced in vitro shoot multiplication at 100 mg/L concentration. The result showed highest significant increase in antioxidant activity by 50 mg/L SA elicited plantlets in terms of DPPH (2,2-Di-phenyl-1-picryl-hydrazyl) free radical scavenging activity (IC50 32.42 ± 0.51), Ferric Reducing Antioxidant Activity (292.73 ± 2.09 mg AAE/g dw) and Metal Chelating Activity (IC50 13.18 ± 0.52). The Gas Chromatography-Mass Spectrometry (GC-MS) profiling revealed presence of 46, 38, 34 and 29 phytochemicals in control, SA1, SA2 and SA3 methanolic extracts respectively. Among the identified compounds, eight compounds, 4H-Pyran-4-one,2,3-dihydro-3,5-dihydroxy-6-methyl; 1,3,4,5-tetrahydroxy-cyclohexanecarboxylic acid; 3,7,11,15-Tetramethyl-2-hexadecen-1-ol (and Phytol); hexadecanoic acid, methyl ester; 9,12-Octadecadienoic acid (Z,Z)-,methyl ester; di-n-octyl phthalate; stigmast-5-en-3-ol,(3.beta.)- or ß- sitosterol; and squalene were previously known for antioxidant potential.

Multilayered regulation of secondary metabolism in medicinal plants

Medicinal plants represent a huge reservoir of secondary metabolites (SMs), substances with significant pharmaceutical and industrial potential. However, obtaining secondary metabolites remains a challenge due to their low-yield accumulation in medicinal plants; moreover, these secondary metabolites are produced through tightly coordinated pathways involving many spatiotemporally and environmentally regulated steps. The first regulatory layer involves a complex network of transcription factors; a second, more recently discovered layer of complexity in the regulation of SMs is epigenetic modification, such as DNA methylation, histone modification and small RNA-based mechanisms, which can jointly or separately influence secondary metabolites by regulating gene expression. Here, we summarize the findings in the fields of genetic and epigenetic regulation with a special emphasis on SMs in medicinal plants, providing a new perspective on the multiple layers of regulation of gene expression.

Shoot Nutrition and Flavor Variation in Two Phyllostachys Species: Does the Quality of Edible Bamboo Shoot Diaphragm and Flesh Differ?

For their quality evaluation, it is essential to determine both bamboo shoot nutrition and palatability, which will have a decisive effect on their economic value and market potential. However, differences in shoot nutrition and flavor variation among bamboo species, positions, and components have not been scientifically validated. This study assessed nutritional and flavor differences in two components (i.e., shoot flesh (BSF) and diaphragm (BSD)) of two Phyllostachys species (i.e., Phyllostachys edulis and Phyllostachys violascens) and analyzed any positional variation. Results showed that BSF protein, starch, fat, and vitamin C contents were comparatively higher. Nutrient compounds in the upper shoot segment of Ph. edulis were higher and contained less cellulose and lignin. However, both species’ BSD total acid, oxalic acid, and tannin contents were comparable. BSD soluble sugar and sugar:acid ratio were higher than upper BSD total amino acid, four key amino acids (i.e., essential amino acid, bitter amino acid, umami amino acid, and sweet amino acid flavor compounds), and associated ratios were all higher than BSF while also being rich in amino acids. The content and proportion of BSF essential and bitter amino acid flavor compounds in Ph. edulis were high relative to Ph. violascens. Conversely, the content and proportion of BSD umami and sweet amino acid flavor compounds were comparable to that of Ph. edulis. Our results showed that bamboo shoot quality was affected by flavor compound differences and that interspecific and shoot components interact. This study offers a new perspective to determine the formative mechanisms involved in bamboo shoot quality while providing a basis for their different usages.

Plant secondary metabolic responses to global climate change: A meta-analysis in medicinal and aromatic plants

Plant secondary metabolites (SMs) play crucial roles in plant-environment interactions and contribute greatly to human health. Global climate changes are expected to dramatically affect plant secondary metabolism, yet a systematic understanding of such influences is still lacking. Here, we employed medicinal and aromatic plants (MAAPs) as model plant taxa and performed a meta-analysis from 360 publications using 1828 paired observations to assess the responses of different SMs levels and the accompanying plant traits to elevated carbon dioxide (eCO₂ ), elevated temperature (eT), elevated nitrogen deposition (eN) and decreased precipitation (dP). The overall results showed that phenolic and terpenoid levels generally respond positively to eCO₂ but negatively to eN, while the total alkaloid concentration was increased remarkably by eN. By contrast, dP promotes the levels of all SMs, while eT exclusively exerts a positive influence on the levels of phenolic compounds. Further analysis highlighted the dependence of SM responses on different moderators such as plant functional types, climate change levels or exposure durations, mean annual temperature and mean annual precipitation. Moreover, plant phenolic and terpenoid responses to climate changes could be attributed to the variations of C/N ratio and total soluble sugar levels, while the trade-off supposition contributed to SM responses to climate changes other than eCO₂ . Taken together, our results predicted the distinctive SM responses to diverse climate changes in MAAPs and allowed us to define potential moderators responsible for these variations. Further, linking SM responses to C-N metabolism and growth-defence balance provided biological understandings in terms of plant secondary metabolic regulation.

Fe-Based Nanomaterial-Induced Root Nodulation Is Modulated by Flavonoids to Improve Soybean (Glycine max) Growth and Quality

Innovative technology to increase efficient nitrogen (N) use while avoiding environmental damages is needed because of the increasing food demand of the rapidly growing global population. Soybean (Glycine max) has evolved a complex symbiosis with N-fixing bacteria that forms nodules to fix N. Herein, foliar application of 10 mg L^-1 Fe₇(PO₄)₆ and Fe₃O₄ nanomaterials (NMs) (Fe-based NMs) promoted soybean growth and root nodulation, thus improving the yield and quality over that of the unexposed control, EDTA-control, and 1 and 5 mg L^-1 NMs. Mechanistically, flavonoids, key signaling molecules at the initial signaling steps in nodulation, were increased by more than 20% upon exposure to 10 mg L^-1 Fe-based NMs, due to enhanced key enzyme (phenylalanine ammonia-lyase, PAL) activity and up-regulation of flavonoid biosynthetic genes (GmPAL, GmC4H, Gm4CL, and GmCHS). Accumulated flavonoids were secreted to the rhizosphere, recruiting rhizobia for colonization. Fe₇(PO₄)₆ NMs increased Allorhizobium by 87.3%, and Fe₃O₄ NMs increased Allorhizobium and Mesorhizobium by 142.2% and 34.9%, leading to increased root nodules by 50.0% and 35.4% over the unexposed control, respectively. Leghemoglobin content was also noticeably improved by 8.2-46.5% upon Fe-based NMs. The higher levels of nodule number and leghemoglobin content resulted in enhanced N content by 15.5-181.2% during the whole growth period. Finally, the yield (pod number and grain biomass) and quality (flavonoids, soluble protein, and elemental nutrients) were significantly increased more than 14% by Fe-based NMs. Our study provides an effective nanoenabled strategy for inducing root nodules to increase N use efficiency, and then both yield and quality of soybean.

A meta-analysis of responses of C3 plants to atmospheric CO2 : dose-response curves for 85 traits ranging from the molecular to the whole-plant level

Generalised dose-response curves are essential to understand how plants acclimate to atmospheric CO₂ . We carried out a meta-analysis of 630 experiments in which C₃ plants were experimentally grown at different [CO₂ ] under relatively benign conditions, and derived dose-response curves for 85 phenotypic traits. These curves were characterised by form, plasticity, consistency and reliability. Considered over a range of 200-1200 µmol mol^-1 CO₂ , some traits more than doubled (e.g. area-based photosynthesis; intrinsic water-use efficiency), whereas others more than halved (area-based transpiration). At current atmospheric [CO₂ ], 64% of the total stimulation in biomass over the 200-1200 µmol mol^-1 range has already been realised. We also mapped the trait responses of plants to [CO₂ ] against those we have quantified before for light intensity. For most traits, CO₂ and light responses were of similar direction. However, some traits (such as reproductive effort) only responded to light, others (such as plant height) only to [CO₂ ], and some traits (such as area-based transpiration) responded in opposite directions. This synthesis provides a comprehensive picture of plant responses to [CO₂ ] at different integration levels and offers the quantitative dose-response curves that can be used to improve global change simulation models.

Zingiber officinale var. rubrum: Red Ginger's Medicinal Uses

Zingiber officinale var. rubrum (red ginger) is widely used in traditional medicine in Asia. Unlike other gingers, it is not used as a spice in cuisines. To date, a total of 169 chemical constituents have been reported from red ginger. The constituents include vanilloids, monoterpenes, sesquiterpenes, diterpenes, flavonoids, amino acids, etc. Red ginger has many therapeutic roles in various diseases, including inflammatory diseases, vomiting, rubella, atherosclerosis, tuberculosis, growth disorders, and cancer. Scientific evidence suggests that red ginger exhibits immunomodulatory, antihypertensive, antihyperlipidemic, antihyperuricemic, antimicrobial, and cytotoxic activities. These biological activities are the underlying causes of red ginger's therapeutic benefits. In addition, there have been few reports on adverse side effects of red ginger. This review aims to provide insights in terms the bioactive constituents and their biosynthesis, biological activities, molecular mechanisms, pharmacokinetics, and qualitative and quantitative analysis of red ginger.

Elucidating the relevance of high temperature and elevated CO2 in plant secondary metabolites (PSMs) production

Plant secondary metabolites (PSMs) are plant products that are discontinuously distributed throughout the plant kingdom. These secondary compounds have various chemical groups and are named according to their chemical constituents. For their ability to defend biotic and abiotic stresses they are considered as plants' defensive compounds. These metabolites take part in plant protection from insects, herbivores, and extreme environmental conditions. They are indirectly involved in plants’ growth and development. Secondary metabolites are also used by people in the form of medicines, pharmaceuticals, agrochemicals, colors, fragrances, flavorings, food additives, biopesticides, and drugs development. However, the increase in atmospheric temperature by several anthropogenic activities majorly by the combustion of hydrocarbons is a great issue now. On the other hand, climate change leaves an impact on the quality and quantity of plant secondary metabolites. It is measured that several greenhouse gases (GHGs) are present in the atmosphere, like Chlorofluorocarbons (CFCs), nitrous oxides (NO_x), Carbon dioxide (CO₂), Methane (CH₄) and Ozone (O₃), etc. CO₂, the major greenhouse gas is essential for photosynthesis. On the other hand, CO₂ plays a significant role in the up-regulation of atmospheric temperature. Plants produce various types of primary metabolites such as carbohydrates, proteins, fats, membrane lipids, nucleic acids, and chlorophyll as well as a variety of secondary metabolites from photosynthesis. The high temperature in the atmosphere creates heat stress for plants. As a matter of fact many morphological, physiological and biochemical changes occur in the plant. The high temperature invariably elicits the production of several secondary metabolites within plants. Various strategies have been universally documented to improve the production of PSMs. With this objective, the focus of the current review is to further investigate and discuss futuristic scenarios the effect of elevated CO₂ and high temperature on PSMs production which may perhaps beneficial for pharmaceutical industries, biotechnology industries, and also in climate change researches.

Hemin-induced increase in saponin content contributes to the alleviation of osmotic and cold stress damage to Conyza blinii in a heme oxygenase 1-dependent manner

Hemin can improve the stress resistance of plants through the heme oxygenase system. Additionally, substances contained in plants, such as secondary metabolites, can improve stress resistance. However, few studies have explored the effects of hemin on secondary metabolite content. Therefore, the effects of hemin on saponin synthesis and the mechanism of plant injury relief by hemin in Conyza blinii were investigated in this study. Hemin treatment promoted plant growth and increased the antioxidant enzyme activity and saponin content of C. blinii under osmotic stress and cold stress. Further study showed that hemin could provide sufficient precursors for saponin synthesis by improving the photosynthetic capacity of C. blinii and increasing the gene expression of key enzymes in the saponin synthesis pathway, thus increasing the saponin content. Moreover, the promotion effect of hemin on saponin synthesis is dependent on heme oxygenase-1 and can be reversed by the inhibitor Zn-protoporphyrin-IX (ZnPPIX). This study revealed that hemin can increase the saponin content of C. blinii and alleviate the damage caused by abiotic stress, and it also broadened the understanding of the relationship between hemin and secondary metabolites in plant abiotic stress relief.

Interactive Impact of Arbuscular Mycorrhizal Fungi and Elevated CO2 on Growth and Functional Food Value of Thymus vulgare

Arbuscular mycorrhizal fungi (AMF) and elevated CO₂ (eCO₂) have been effectively integrated to the agricultural procedures as an ecofriendly approach to support the production and quality of plants. However, less attention has been given to the synchronous application of AMF and eCO₂ and how that could affect the global plant metabolism. This study was conducted to investigate the effects of AMF and eCO₂, individually or in combination, on growth, photosynthesis, metabolism and the functional food value of Thymus vulgare. Results revealed that both AMF and eCO₂ treatments improved the photosynthesis and biomass production, however much more positive impact was obtained by their synchronous application. Moreover, the levels of the majority of the detected sugars, organic acids, amino acids, unsaturated fatty acids, volatile compounds, phenolic acids and flavonoids were further improved as a result of the synergistic action of AMF and eCO₂, as compared to the individual treatments. Overall, this study clearly shows that co-application of AMF and eCO₂ induces a synergistic biofertilization impact and enhances the functional food value of T. vulgare by affecting its global metabolism.

Global metabolic changes induced by arbuscular mycorrhizal fungi in oregano plants grown under ambient and elevated levels of atmospheric CO2

Symbiotic plant-microorganisms interaction is a promising approach to avoid the environmental hazards of synthetic fertilizers and pesticides. Among these, arbuscular mycorrhizal fungi (AMF) are known to improve the growth and quality of many plant species; however the detailed metabolic mechanisms behind such beneficial effects are far from complete. Further, elevated levels of atmospheric CO₂ (eCO₂) could affect such AMF-plant association. Herein, we have investigated the individual and synchronous impact of AMF and eCO₂ (620 ppm) on nutrient uptake, growth, photosynthesis, respiration, and levels of primary and secondary metabolites in oregano (Oreganum vulgare), an economically important herbal plant. Enhanced AMF colonization rate and a better mycelial growth were observed in roots of oregano grown under eCO₂. Both AMF and eCO₂ treatments significantly enhanced the growth and photosynthesis of oregano plants, however much improvements were observed by their synchronous application. eCO₂ further increased the AMF-induced dark respiration and accumulation of macro and microelements. Hierarchical clustering analysis of individual primary and secondary metabolites revealed a metabolite-dependent response toward AMF and eCO₂. The synchronous application of AMF and eCO₂ resulted in promoted accumulation of the majority of the detected sugars, organic acids, amino acids, unsaturated fatty acids, phenolic acids and flavonoids, as compared with the sole treatments. Moreover, AMF and eCO₂ acted synergistically in improving the antioxidant capacity and anti-lipid peroxidation activity of oregano. Therefore, this study suggests that AMF treatment induces a global metabolic change in oregano, the effect that is strengthened under eCO₂.

Nitrogen drives plant growth to the detriment of leaf sugar and steviol glycosides metabolisms in Stevia (Stevia rebaudiana Bertoni)

Steviol glycosides (SGs) in Stevia (Stevia rebaudiana Bertoni) leaves are important due to their high sweetness and low calorific value. The yield of SGs is dependent on fertilization regimes, but the relationship between nitrogen (N) administration and SGs synthesis is still unclear. In this study, we investigate the effects of N rates on SGs production through hydroponic and plot experiments. The SGs yield was not significantly changed by N fertilization, but leaf SGs concentrations were significantly reduced due to the "dilution effect". Additionally, N addition decreased leaf carbon (C)/N ratio and soluble sugar concentration, accompanied with the inhibited phosphoenolpyruvate carboxylase and L-phenylalanine ammonia_lyase activities. A significant positive correlation between leaf SGs concentrations, C/N ratio and soluble sugar concentration was observed. Overall, we suggest that N-driven Stevia growth negatively affects SGs concentrations. The leaf C/N ratio and soluble sugar changes indicated the occurrence of metabolic reprogramming.

Biochemical composition and antioxidant activity affected by spraying potassium sulfate in black grape (Vitis vinifera L. cv. Rasha)

BACKGROUND

The physiological and metabolic processes involved with grapevine growth and production are influenced by key macro- and micronutrients. Potassium is an essential plant nutrient that affects growth and fruit quality. In this study, the impact of foliar spraying of potassium sulfate (K₂ SO₄ ) on qualitative characteristics of grape berries was evaluated in the cultivar 'Rasha', a commonly cultivated cultivar in Kurdistan province of Iran. Leaves of the fully grown vines were sprayed with each of the 1.5 and 3 g L^-1 K₂ SO₄ solutions once (1 month after petal senescence) and twice (15 days after first spraying). The control plants were sprayed with distilled water. Various biochemical contents and enzyme activities on the ripe berries were analyzed.

RESULTS

Significant increases in anthocyanin, total protein content, and antioxidant enzyme activities were observed in the berries treated twice with 3 g L^-1 K₂ SO₄ . Concentrations of total carbohydrate, phenol, and antioxidant activity in berries sprayed with K₂ SO₄ were higher than in the controls. We observed a strong correlation between antioxidant activity and different phenolic compounds.

CONCLUSION

These findings suggest that K₂ SO₄ treatment influences biosynthesis of phenolic compounds and antioxidant enzymes. Thus, treatment by K₂ SO₄ could improve nutritional and qualitative attributes of grape. © 2018 Society of Chemical Industry.

Assessment and comparison of phytochemical constituents and biological activities of bitter bean (Parkia speciosa Hassk.) collected from different locations in Malaysia

Background

Parkia speciosa seeds are a common ingredient in Malay cuisine with traditional interest because of its medicinal importance and content of health-promoting phytochemicals. This study evaluated the phytochemical constituents and biological activities (antioxidant and antibacterial activities) of Parkia speciosa Hassk seeds collected from three different regions of Malaysia (Perak, Negeri Sembilan and Johor). Phytochemical constituents (total flavonoid and total phenolic) were measured using the spectrophotometric method, and individual flavonoids and phenolic acids were identified using ultra-high-performance liquid chromatography. Ferric reducing antioxidant potential (FRAP) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay we used in order to evaluation of antioxidant activities. Disc diffusion method was employed for the evaluation of antibacterial activity of extracts against Gram-positive and Gram-negative bacterial strains.

Results

The primary screening of phytochemicals showed that P. speciosa seeds contain alkaloids, terpenoids, flavonoids, and phenolics. Samples collected from Perak contained the highest levels of the phytochemical constituents, with highest DPPH and FRAP activity followed by Negeri sembilan and Johor. From the identified compounds, quercetin and gallic acid were identified as the most abundant compounds. Seeds collected from the Perak location exhibited potent antibacterial activity, against both Gram-positive and Gram-negative bacteria strains. Staphylococcus aureus and Bacillus subtilis were recorded as the bacterial strains most sensitive to P. speciosa seed extracts. Correlation analysis showed that flavonoid compounds are responsible for the antioxidant activities of the P. speciosa seeds studied, while antibacterial activity showed a high correlation with the levels of gallic acid.

Conclusions

Parkia speciosa seed grown in Perak exhibit the highest concentrations of phytochemicals, as well as the highest biological activity. It may also be recommended for the food industry to use seeds from this area for their products, which are going to compete in the expanding functional food markets.

Stimulation in primary and secondary metabolism by elevated carbon dioxide alters green tea quality in Camellia sinensis L

Rising CO₂ concentration, a driving force of climate change, is impacting global food security by affecting plant physiology. Nevertheless, the effects of elevated CO₂ on primary and secondary metabolism in tea plants (Camellia sinensis L.) still remain largely unknown. Here we showed that exposure of tea plants to elevated CO₂ (800 µmol mol⁻¹ for 24 d) remarkably improved both photosynthesis and respiration in tea leaves. Furthermore, elevated CO₂ increased the concentrations of soluble sugar, starch and total carbon, but decreased the total nitrogen concentration, resulting in an increased carbon to nitrogen ratio in tea leaves. Among the tea quality parameters, tea polyphenol, free amino acid and theanine concentrations increased, while the caffeine concentration decreased after CO₂ enrichment. The concentrations of individual catechins were altered differentially resulting in an increased total catechins concentration under elevated CO₂ condition. Real-time qPCR analysis revealed that the expression levels of catechins and theanine biosynthetic genes were up-regulated, while that of caffeine synthetic genes were down-regulated in tea leaves when grown under elevated CO₂ condition. These results unveiled profound effects of CO₂ enrichment on photosynthesis and respiration in tea plants, which eventually modulated the biosynthesis of key secondary metabolites towards production of a quality green tea.

Potassium and zinc increase tolerance to salt stress in wheat (Triticum aestivum L.)

Potassium and zinc are essential elements in plant growth and metabolism and plays a vital role in salt stress tolerance. To investigate the physiological mechanism of salt stress tolerance, a pot experiment was conducted. Potassium and zinc significantly minimize the oxidative stress and increase root, shoot and spike length in wheat varieties. Fresh and dry biomass were significantly increased by potassium followed by zinc as compared to control C. The photosynthetic pigment and osmolyte regulator (proline, total phenolic, and total carbohydrate) were significantly enhanced by potassium and zinc. Salt stress increases MDA content in wheat varieties while potassium and zinc counteract the adverse effect of salinity and significantly increased membrane stability index. Salt stress decreases the activities of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) while the exogenous application of potassium and zinc significantly enhanced the activities of these enzymes. A significant positive correlation was found of spike length with proline (R² = 0.966 ^∗∗∗), phenolic (R² = 0.741^∗) and chlorophyll (R² = 0.853^∗∗). The MDA content showed significant negative correlation (R² = 0.983^∗∗∗) with MSI. It is concluded that potassium and zinc reduced toxic effect of salinity while its combine application showed synergetic effect and significantly enhanced salt tolerance.

The regulation by phenolic compounds of soil organic matter dynamics under a changing environment

Phenolics are the most abundant plant metabolites and are believed to decompose slowly in soils compared to other soil organic matter (SOM). Thus, they have often been considered as a slow carbon (C) pool in soil dynamics models. Here, however, we review changes in our concept about the turnover rate of phenolics and quantification of different types of phenolics in soils. Also, we synthesize current research on the degradation of phenolics and their regulatory effects on decomposition. Environmental changes, such as elevated CO₂, warming, nitrogen (N) deposition, and drought, could influence the production and form of phenolics, leading to a change in SOM dynamics, and thus we also review the fate of phenolics under environmental disturbances. Finally, we propose the use of phenolics as a tool to control rates of SOM decomposition to stabilize organic carbon in ecosystems. Further studies to clarify the role of phenolics in SOM dynamics should include improving quantification methods, elucidating the relationship between phenolics and soil microorganisms, and determining the interactive effects of combinations of environmental changes on the phenolics production and degradation and subsequent impact on SOM processing.

Tomato-Pseudomonas syringae interactions under elevated CO₂ concentration: the role of stomata

Increasing atmospheric CO₂ concentrations ([CO₂]) in agricultural and natural ecosystems is known to reduce plant stomatal opening, but it is unclear whether these CO₂-induced stomatal alterations are associated with foliar pathogen infections. In this study, tomato plants were grown under ambient and elevated [CO₂] and inoculated with Pseudomonas syringae pv. tomato strain DC3000, a strain that is virulent on tomato plants. We found that elevated [CO₂] enhanced tomato defence against P. syringae. Scanning electron microscopy analysis revealed that stomatal aperture of elevated [CO₂] plants was considerably smaller than their ambient counterparts, which affected the behaviour of P. syringae bacteria on the upper surface of epidermal peels. Pharmacological experiments revealed that nitric oxide (NO) played a role in elevated [CO₂]-induced stomatal closure. Silencing key genes involved in NO generation and stomatal closing, nitrate reductase (NR) and guard cell slow-type anion channel 1 (SLAC1), blocked elevated [CO₂]-induced stomatal closure and resulted in significant increases in P. syringae infection. However, the SLAC1-silenced plants, but not the NR-silenced plants, still had significantly higher defence under elevated [CO₂] compared with plants treated with ambient [CO₂]. Similar results were obtained when the stomata-limiting factor for P. syringae entry was excluded by syringe infiltration inoculation. These results indicate that elevated [CO₂] induces defence against P. syringae in tomato plants, not only by reducing the stomata-mediated entry of P. syringae but also by invoking a stomata-independent pathway to counteract P. syringae. This information is valuable for designing proper strategies against bacterial pathogens under changing agricultural and natural ecosystems.

Efficacy and safety of ginger in osteoarthritis patients: a meta-analysis of randomized placebo-controlled trials

The aim of this study was to assess the clinical efficacy and safety of oral ginger for symptomatic treatment of osteoarthritis (OA) by carrying out a systematic literature search followed by meta-analyses on selected studies. Inclusion criteria were randomized controlled trials (RCTs) comparing oral ginger treatment with placebo in OA patients aged >18 years. Outcomes were reduction in pain and reduction in disability. Harm was assessed as withdrawals due to adverse events. The efficacy effect size was estimated using Hedges' standardized mean difference (SMD), and safety by risk ratio (RR). Standard random-effects meta-analysis was used, and inconsistency was evaluated by the I-squared index (I(2)). Out of 122 retrieved references, 117 were discarded, leaving five trials (593 patients) for meta-analyses. The majority reported relevant randomization procedures and blinding, but an inadequate intention-to-treat (ITT) analysis. Following ginger intake, a statistically significant pain reduction SMD = -0.30 ([95% CI: [(-0.50, -0.09)], P = 0.005]) with a low degree of inconsistency among trials (I(2) = 27%), and a statistically significant reduction in disability SMD = -0.22 ([95% CI: ([-0.39, -0.04)]; P = 0.01; I(2) = 0%]) were seen, both in favor of ginger. Patients given ginger were more than twice as likely to discontinue treatment compared to placebo ([RR = 2.33; 95% CI: (1.04, 5.22)]; P = 0.04; I(2) = 0%]). Ginger was modestly efficacious and reasonably safe for treatment of OA. We judged the evidence to be of moderate quality, based on the small number of participants and inadequate ITT populations. Prospero: CRD42011001777.

Allocation of secondary metabolites, photosynthetic capacity, and antioxidant activity of Kacip Fatimah (Labisia pumila Benth) in response to CO2 and light intensity

A split plot 3 by 4 experiment was designed to investigate and distinguish the relationships among production of secondary metabolites, soluble sugar, phenylalanine ammonia lyase (PAL; EC 4.3.1.5) activity, leaf gas exchange, chlorophyll content, antioxidant activity (DPPH), and lipid peroxidation under three levels of CO2 (400, 800, and 1200 μ mol/mol) and four levels of light intensity (225, 500, 625, and 900 μ mol/m(2)/s) over 15 weeks in Labisia pumila. The production of plant secondary metabolites, sugar, chlorophyll content, antioxidant activity, and malondialdehyde content was influenced by the interactions between CO2 and irradiance. The highest accumulation of secondary metabolites, sugar, maliondialdehyde, and DPPH activity was observed under CO2 at 1200 μ mol/mol + light intensity at 225 μ mol/m(2)/s. Meanwhile, at 400 μ mol/mol CO2 + 900 μ mol/m(2)/s light intensity the production of chlorophyll and maliondialdehyde content was the highest. As CO2 levels increased from 400 to 1200 μ mol/mol the photosynthesis, stomatal conductance, f v /f m (maximum efficiency of photosystem II), and PAL activity were enhanced. The production of secondary metabolites displayed a significant negative relationship with maliondialdehyde indicating lowered oxidative stress under high CO2 and low irradiance improved the production of plant secondary metabolites that simultaneously enhanced the antioxidant activity (DPPH), thus improving the medicinal value of Labisia pumila under this condition.

Impact of organic and inorganic fertilizers application on the phytochemical and antioxidant activity of Kacip Fatimah (Labisia pumila Benth)

A study was conducted to compare secondary metabolites and antioxidant activity of Labisia pumila Benth (Kacip Fatimah) in response to two sources of fertilizer [i.e., organic (chicken dung; 10% N:10% P₂O₅:10% K₂O) and inorganic fertilizer (NPK green; 15% N, 15% P₂O₅, 15% K₂O)] under different N rates of 0, 90, 180 and 270 kg N/ha. The experiment was arranged in a randomized complete block design replicated three times. At the end of 15 weeks, it was observed that the application of organic fertilizer enhanced the production of total phenolics, flavonoids, ascorbic acid, saponin and gluthathione content in L. pumila, compared to the use of inorganic fertilizer. The nitrate content was also reduced under organic fertilization. The application of nitrogen at 90 kg N/ha improved the production of secondary metabolites in Labisia pumila. Higher rates in excess of 90 kg N/ha reduced the level of secondary metabolites and antioxidant activity of this herb. The DPPH and FRAP activity was also highest at 90 kg N/ha. The results indicated that the use of chicken dung can enhance the production of secondary metabolites and improve antioxidant activity of this herb.

Interactive effect of salicylic acid on some physiological features and antioxidant enzymes activity in ginger (Zingiber officinale Roscoe)

The effect of foliar salicylic acid (SA) applications (10⁻³ and 10⁻⁵ M) on activities of nitrate reductase, guaiacol peroxidase (POD), superoxide dismutases (SOD), catalase (CAT) and proline enzymes and physiological parameters was evaluated in two ginger varieties (Halia Bentong and Halia Bara) under greenhouse conditions. In both varieties, tested treatments generally enhanced photosynthetic rate and total dry weight. Photosynthetic rate increases were generally accompanied by increased or unchanged stomatal conductance levels, although intercellular CO₂ concentrations of treated plants were typically lower than in controls. Lower SA concentrations were generally more effective in enhancing photosynthetic rate and plant growth. Exogenous application of SA increased antioxidant enzyme activities and proline content; the greatest responses were obtained in plants sprayed with 10⁻⁵ M SA, with significant increases observed in CAT (20.1%), POD (45.2%), SOD (44.1%) and proline (43.1%) activities. Increased CAT activity in leaves is naturally expected to increase photosynthetic efficiency and thus net photosynthesis by maintaining a constant CO₂ supply. Our results support the idea that low SA concentrations (10⁻⁵ M) may induce nitrite reductase synthesis by mobilizing intracellular NO³⁻ and can provide protection to nitrite reductase degradation in vivo in the absence of NO³⁻. Observed positive correlations among proline, SOD, CAT and POD activities in the studied varieties suggest that increased SOD activity was accompanied by increases in CAT and POD activities because of the high demands of H₂O₂ quenching.

Combined effect of CO(2) enrichment and foliar application of salicylic acid on the production and antioxidant activities of anthocyanin, flavonoids and isoflavonoids from ginger

BACKGROUND

The increase in atmospheric CO(2) concentration caused by climate change and agricultural practices is likely to affect biota by producing changes in plant growth, allocation and chemical composition. This study was conducted to evaluate the combined effect of the application of salicylic acid (SA, at two levels: 0 and 10-3 M) and CO(2) enrichment (at two levels: 400 and 800 μmol·mol-1) on the production and antioxidant activities of anthocyanin, flavonoids and isoflavonoids from two Malaysian ginger varieties, namely Halia Bentong and Halia Bara.

METHODS

High-performance liquid chromatography (HPLC) with photodiode array detection and mass spectrometry was employed to identify and quantify the flavonoids and anthocyanins in the ginger extracts. The antioxidant activity of the leaf extracts was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and thiobarbituric acid (TBA) assays. The substrate specificity of chalcone synthase, the key enzyme for flavonoid biosynthesis, was investigated using the chalcone synthase (CHS) assay.

RESULTS

CO(2) levels of 800 μmol·mol-1 significantly increased anthocyanin, rutin, naringenin, myricetin, apigenin, fisetin and morin contents in ginger leaves. Meanwhile, the combined effect of SA and CO(2) enrichment enhanced anthocyanin and flavonoid production compared with single treatment effects. High anthocyanin content was observed in H Bara leaves treated with elevated CO(2) and SA. The highest chalcone synthase (CHS) activity was observed in plants treated with SA and CO(2) enrichment. Plants not treated with SA and kept under ambient CO(2) conditions showed the lowest CHS activity. The highest free radical scavenging activity corresponded to H Bara treated with SA under high CO(2) conditions, while the lowest activity corresponded to H Bentong without SA treatment and under atmospheric CO(2) levels. As the level of CO(2) increased, the DPPH activity increased. Higher TBA activity was also recorded in the extracts of H Bara treated with SA and grown under high CO(2) conditions.

CONCLUSIONS

The biological activities of both ginger varieties were enhanced when the plants were treated with SA and grown under elevated CO(2) concentration. The increase in the production of anthocyanin and flavonoids in plants treated with SA could be attributed to the increase in CHS activity under high CO(2) levels.

Primary, secondary metabolites, photosynthetic capacity and antioxidant activity of the Malaysian Herb Kacip Fatimah (Labisia Pumila Benth) exposed to potassium fertilization under greenhouse conditions

A randomized complete block design was used to characterize the relationship between production of total phenolics, flavonoids, ascorbic acid, carbohydrate content, leaf gas exchange, phenylalanine ammonia-lyase (PAL), soluble protein, invertase and antioxidant enzyme activities (ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) in Labisia pumila Benth var. alata under four levels of potassium fertilization experiments (0, 90, 180 and 270 kg K/ha) conducted for 12 weeks. It was found that the production of total phenolics, flavonoids, ascorbic acid and carbohydrate content was affected by the interaction between potassium fertilization and plant parts. As the potassium fertilization levels increased from 0 to 270 kg K/ha, the production of soluble protein and PAL activity increased steadily. At the highest potassium fertilization (270 kg K/ha) L. pumila exhibited significantly higher net photosynthesis (A), stomatal conductance (g_s), intercellular CO₂ (C_i), apparent quantum yield (ξ) and lower dark respiration rates (R_d), compared to the other treatments. It was found that the production of total phenolics, flavonoids and ascorbic acid are also higher under 270 kg K/ha compared to 180, 90 and 0 kg K/ha. Furthermore, from the present study, the invertase activity was also found to be higher in 270 kg K/ha treatment. The antioxidant enzyme activities (APX, CAT and SOD) were lower under high potassium fertilization (270 kg K/ha) and have a significant negative correlation with total phenolics and flavonoid production. From this study, it was observed that the up-regulation of leaf gas exchange and downregulation of APX, CAT and SOD activities under high supplementation of potassium fertilizer enhanced the carbohydrate content that simultaneously increased the production of L. pumila secondary metabolites, thus increasing the health promoting effects of this plant.

Involvement of salicylic acid on antioxidant and anticancer properties, anthocyanin production and chalcone synthase activity in ginger (Zingiber officinale Roscoe) varieties

The effect of foliar application of salicylic acid (SA) at different concentrations (10-3 M and 10-5 M) was investigated on the production of secondary metabolites (flavonoids), chalcone synthase (CHS) activity, antioxidant activity and anticancer activity (against breast cancer cell lines MCF-7 and MDA-MB-231) in two varieties of Malaysian ginger, namely Halia Bentong and Halia Bara. The results of high performance liquid chromatography (HPLC) analysis showed that application of SA induced the synthesis of anthocyanin and fisetin in both varieties. Anthocyanin and fisetin were not detected in the control plants. Accordingly, the concentrations of some flavonoids (rutin and apigenin) decreased significantly in plants treated with different concentrations of SA. The present study showed that SA enhanced the chalcone synthase (CHS) enzyme activity (involving flavonoid synthesis) and recorded the highest activity value of 5.77 nkat /mg protein in Halia Bara with the 10-5 M SA treatment. As the SA concentration was decreased from 10-3 M to 10-5 M, the free radical scavenging power (FRAP) increased about 23% in Halia Bentong and 10.6% in Halia Bara. At a concentration of 350 μg mL-1, the DPPH antioxidant activity recorded the highest value of 58.30%-72.90% with the 10-5 M SA treatment followed by the 10-3 M SA (52.14%-63.66%) treatment. The lowest value was recorded in the untreated control plants (42.5%-46.7%). These results indicate that SA can act not only as an inducer but also as an inhibitor of secondary metabolites. Meanwhile, the highest anticancer activity against MCF-7 and MDA-MB-231 cell lines was observed for H. Bara extracts treated with 10-5 M SA with values of 61.53 and 59.88%, respectively. The results suggest that the high anticancer activity in these varieties may be related to the high concentration of potent anticancer components including fisetin and anthocyanin. The results thus indicate that the synthesis of flavonoids in ginger can be increased by foliar application of SA in a controlled environment and that the anticancer activity in young ginger extracts could be improved.