Accumulation Of Total Phenolic Content Research Articles

Effect of drought stress on the expression pattern of genes involved in ABA biosynthesis in Desi-type chickpea (Cicer arietinum L.).

The behavior of Abscisic acid (ABA) as a stress phytohormone may be involved in mechanisms leading to tolerance and survival in adverse environmental conditions such as drought stress. Here, we evaluated ABA-mediated responses at physio-biochemical and molecular levels in drought-stressed seedlings of two different Desi-type chickpea genotypes (10 as a tolerant genotype and 247 as a sensitive one). Under drought stress, two chickpea genotypes showed a decrease in their relative water content (RWC), and the intense decrease was related to the sensitive genotype (73.9%) in severe stress. Hydrogen peroxide (H2O2) and malondialdehyde (MDA) concomitant with the severity of stress increased in genotypes and the higher increase was in the sensitive genotype (5.8-fold and 3.43-fold, respectively). In the tolerant genotype, the enhanced accumulation of total phenolic content (1.75-fold) and radical scavenging action, based on 1,1-diphenyl-2-picrylhydrazyl test (DPPH), (1.69-fold) were simultaneous with ABA accumulation (1.53-fold). In the tolerant genotype, transcriptional analysis presented upregulation of Zeaxanthin epoxidase (ZEP) (1.35-fold), 9-cis-epoxycarotenoid dioxygenase (NCED) (5.16-fold), and Abscisic aldehyde oxidase (AAO) (1.52-fold compared to control conditions) genes in severe stress in comparison with mild stress. The sensitive genotype had a declining trend in total chlorophyll (up to 70%) and carotenoid contents (36%). The main conclusion to be drawn from this investigation is that ABA with its regulatory effects can affect drought tolerance mechanisms to alleviate adverse effects of unsatisfactory environmental conditions. In this paper, we tried to indicate that drought stress induces overexpression of genes triggering ABA-mediated drought responses simultaneously in two genotypes while more increment expression was related to the tolerant genotype. At first thought, it seems that the tolerant genotype compared to the sensitive genotype has a genetically inherent ability to cope with and drop adverse effects of drought stress through over-accumulation of ABA as drought.

Effects of Different Solvents on the Extraction of Phenolic and Flavonoid Compounds, and Antioxidant Activities, in Scutellaria baicalensis Hairy Roots

The hairy roots (HRs) of Scutellaria baicalensis are widely used and consumed worldwide as a medicine, especially in Asian countries, due to their biological and pharmacological activities. The HRs of this plant are rich in secondary metabolites. However, the optimal method and solvents for the extraction of secondary metabolites from S. baicalensis HRs have not been well studied. Therefore, in this study, S. baicalensis HRs were extracted with different solvents, including water (WE), 99.9% pure methanol (PM), 70% aqueous methanol (AM), 99.9% pure ethanol (PE), and 70% aqueous ethanol (AE). The phenolic and flavonoid compounds and various antioxidant activities of each extract were measured. The AE extract (16.85 ± 0.15%) had a higher yield, which led to the highest accumulation of total phenolic content (TPC) and total flavonoid content (TFC), and antioxidant activity. The TPC and TFC were highest in AE (66.03 ± 0.44 mg GAE/g and 40.11 ± 1.31 mg QE/g, respectively), whereas WE, PM, and PE showed lower values in all assays. In addition, the highest antioxidant activities, such as DPPH, ABTS, and SOD-like scavenging activities and reducing power, were achieved in the AE extract compared to the other solvent extracts. Based on these results, the AE extract showed the highest phenolic and flavonoid accumulation and antioxidant activities, highlighting its potential use in the manufacture of useful materials from S. baicalensis HRs and its novel applications.

Pullulan-Based Active Coating Incorporating Potassium Metabisulfite Maintains Postharvest Quality and Induces Disease Resistance to Soft Rot in Kiwifruit.

Soft rot is a severe postharvest disease of kiwifruit that causes enormous economic losses annually. In this study, we aimed to explore an effective pullulan-based active coating, incorporating food additives to reduce soft rot and extend the shelf life of cold-stored kiwifruit. The results showed that 1 g/L potassium metabisulfite could completely inhibit the mycelial growth of Diaporthe sp., Botryosphaeria dothidea, Phomopsis sp. and Alternaria sp., which were the primary pathogens of kiwifruit soft rot. Furthermore, the pullulan coating, combined with a 10 g/L potassium metabisulfite group, had a decay rate 46% lower than the control (CK) group and maintained fruit quality at the end of shelf life. The retention of physicochemical properties such as soluble solid content (SSC), firmness, weight loss and respiration rate also confirmed the efficacy of the treatment. In addition, at the end of shelf life, pullulan coating, combined with potassium metabisulfite, increased the accumulation of total phenolic content (37.59%) and flavonoid content (9.28%), maintained a high energy charge (51.36%), and enhanced superoxide dismutase (SOD) (6.27%), peroxidase (POD) (62.50%), catalase (CAT) (84.62%) and phenylalanine ammonia lyase (PAL) (24.61%) enzyme activities as well as initiating the upregulation of their gene expression levels. As a result, the disease resistance of fruit was improved, and the occurrence of soft rot was delayed. Overall, this study demonstrated that using the pullulan-based active coating incorporating potassium metabisulfite treatment effectively controlled soft rot and retarded the senescence of postharvest kiwifruit.

Alterations in plant anatomy and higher lignin synthesis provides drought tolerance in cluster bean [Cyamopsis tetragonoloba (L.) Taub.

Four contrasting varieties of guar, RGC-1002 and RGC-1038, drought tolerant, while, Sarada and RGC-936, drought sensitive, were monitored in watered and drought. The water status, phenolics, plant anatomy and transcript level of genes related to anatomical traits were assessed. The study aimed to decipher the anatomical adaptations of guar plants in response to water stress. The physiological determinants, relative water content (RWC), water potential (ψ), and leaf membrane damage, declined under drought in all four varieties although, the decrement was lesser in the tolerant varieties. Furthermore, the tolerant cultivars subjected to water stress recorded higher accumulation of total phenolic content, anthocyanin and lignin, which efficiently scavenge the reactive oxygen species. The results suggest that the cultivars RGC-1002 and RGC-1038 are better able to resist drought-induced oxidative stress than Sarada and RGC-936. Moreover, leaf, petiole, stem and root anatomical traits viz. size of epidermal cell, parenchyma, width of cortex layer, and diameter of xylem vessels were narrowed in all the varieties although, the decrement was lesser in the tolerant varieties under drought. The expression analysis of genes revealed that drought-tolerant varieties showed enhanced mechanical support for water conduction by up-regulation of genes, Phenylalanine ammonia-lyase1 (PAL1), cinnamate-4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), cinnamoyl-CoA reductase (CCR), caffeoyl-CoA O-methyltransferase (CCOMT), and cinnamyl-alcohol dehydrogenase (CAD6) in water stress conditions. The alterations in physio-anatomical, biochemical and gene expression traits in tolerant guar varieties enabled them to maintain steady nutrient transport while reducing the risk of embolisms and increasing water-flow resistance for better survival in water stressed conditions.

Fungal endophytes from medicinal plant Bletilla striata (Thunb.) Reichb. F. promote the host plant growth and phenolic accumulation

Endophytic fungi are capable of increasing the growth and secondary metabolite production of medicinal plants in an ecofriendly and sustainable manner. Although these responses have been demonstrated in many plant species, they are not well understood in the medicinal plant Bletilla striata (Thunb.) Reichb.F.. Co-culture of B.striata with three endofungal isolates was carried out to evaluate the effects of endophytic fungal interaction on the plant growth and accumulation of phenols. The plant growth-promoting traits of isolated fungi were investigated, and the isolates had the ability to produce indole-3-acetic acid (IAA), siderophore and cellulolytic enzyme. The fungal strain Byssochlamys spectabilis 1-N2 co-cultured with plantlets of B. striata significantly increased certain growth properties, including shoot length by 71.40%, pseudobulbs dry weight by 52.58%, number of new roots by 5.25-fold, pseudobulbs diameter by 30.94% and improved the total phenolic content of the medicinal part by 25.41%. The fungal polysaccharide elicitor prepared from B.spectabilis 1-N2 mycelium also altered the accumulation of total phenolic content at different time points. Polysaccharide elicitor treatment significantly enhanced the accumulation of nitric oxide (NO) and salicylic acid (SA), which are involved in the plant defence response and significantly upregulated the activities of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H) and tyrosine ammonia lyase (TAL). The findings of this study contribute to our understanding of B. striata and endophytic fungi interactions and provide vital information for the use of endophytic fungi to improve plant growth and active component accumulation in B.striata cultivation.

Nitrogen levels, plant density and postharvest storage duration affect phytochemical and antioxidant properties of field-grown basil and rocket crops

ABSTRACT Growers usually apply elevated nitrogen levels when plants are established at high densities to obtain improved yields. It is not known how this practice affects phytochemical and antioxidant properties of basil (Ocimum basilicum L.) and rocket [Diplotaxis tenuifolia (L.) DC]) during postharvest storage, which are important quality aspects of these crops for human health. This study investigated effects of N application (60, 90, 120, 150, or 180 kg.ha−1), plant density (40,000; 62,500 and 93,750 plants.ha−1 for basil; 40,000; 80,000 and 133,333 plants.ha−1 for rocket), and postharvest storage duration (0, 5, 10 or 15 days) on phytochemical and antioxidant properties of basil and rocket. After harvest, leaves were packaged in biaxially oriented polypropylene (anti-mist) bags and kept at 12°C and 85% relative humidity in a cold temperature room. Nitrogen application of 120 kg.ha−1 at day 0 of storage, caused the highest accumulation of total phenolic content (TPC), flavonoid content (FC), strong free radical scavenging activity, and % antioxidant with limited effect due to plant density on basil. In rocket, application of 60 to 120 kg.ha−1 N at day 0 of storage had high TPC; FC was high at 90 to 180 kg.ha−1 N and 10 days of storage. Rocket had strong scavenging activity, as a result of 120 to 180 kg.ha−1 N, at 15 days of storage, and for 60 and 90 kg.ha−1 N at 0 and 10 days of storage. Postharvest quality of basil was affected by storage time and N application; TPC, FC, and free radical scavenging activity (FRS) were reduced as storage time lengthened. Rocket had improved postharvest quality at 10 days of storage. Spacing had limited effect on all parameters in basil and rocket. The most economic treatment in basil was 60 kg.ha−1 N for TPC, FC, FRS, and antioxidant activity; in rocket, it was 120 kg.ha−1 with longer shelf-life of 10 days of storage with regard to antioxidant activity. Optimization of agronomic practises for improved production should consider phytochemical quality assurance to ensure crop health benefits to consumers are not compromised.

Total Phenolic Content, Peroxidase and Polyphenoloxidase Activities in Ganoderma Infected Oil Palm Seedlings – Inoculated with Arbuscular Mycorrhiza Fungi (AMF)

Basal stem rot disease caused by Ganoderma boninense is the most predominant disease of oil palm plantations in Southeast Asia. Although an effective method for controlling the disease is elusive, research towards early detection and remedy for disease control measures remains crucial for plantation operation. Arbuscular mycorrhiza fungi (AMF) offers a practical alternative that should be seriously considered and implemented. This study evaluated the enzyme activities (TPC, PPO, PO activity) in oil palm seedlings inoculated with arbuscular mycorrhizal fungi (AMF) and infected with G. boninense. Artificial inoculation was conducted using oil palm germinated seeds in the nursery, and plant responses were analysed at 8, 12, 16, and 20 weeks of post-inoculation (WPI). At 20 WPI, the highest accumulation of total phenolic content (TPC) was recorded in T3 (AMF + G. boninense) with 6.09 mg/g compared to T1 (untreated), T2 (G. boninense), and T4 (AMF), which recorded TPC of 3.24 mg/g, 4.19 mg/g and 3.87 mg/g respectively with no significant difference indicating the natural presence of phenol compound in healthy tissue at concentration enough for defense, whether as free compound or in the conjugated form which released after the attack. Both T2 and T3 showed higher peroxidase (PO) levels with 122.8 unit/g tissue and 116.5 unit/g tissue compared to T1 (73.63 unit/g tissue) and T4 (80.6 unit/g tissue). The polyphenoloxidase (PPO) activity was also higher in both T2 (142.3 unit/g tissue) and T3 (111.7 unit/g tissue) compared to T1 (55.3 unit/g tissue) and T4 (36.3 unit/g tissue). Seedlings treated with AMF also showed increased plant growth compared to untreated seedlings. It was observed that T3 seedlings with AMF prophylactic treatment showed the highest chlorophyll content even with G. boninense infection.

Biochemical and Gene Expression Analyses in Different Poplar Clones: The Selection Tools for Afforestation of Halomorphic Environments

Halomorphic soils cover a significant area in the Vojvodina region and represent ecological and economic challenges for agricultural and forestry sectors. In this study, four economically important Serbian poplar clones were compared according to their biochemical and transcriptomic responses towards mild and severe salt stress to select the most tolerant clones for afforestation of halomorphic soils. Three prospective clones of Populus deltoides (Bora-B229, Antonije-182/81 and PE19/66) and one of hybrid genetic background P. nigraxP. deltoides, e.g., P. x euramericana (Pannonia-M1) were hydroponically subjected to NaCl as a salt stress agent in a concentration range from 150 mM to 450 mM. Plant responses were measured at different time periods in the leaves. Biochemical response of poplar clones to salt stress was estimated by tracking several parameters such as different radical scavenging capacities (estimated by DPPH, FRAP and ABTS assays), accumulation of total phenolic content and flavonoids. Furthermore, accumulation of two osmolytes, glycine betaine and proline, were quantified. The genetic difference of those clones has been already shown by single nucleotide polymorphisms (SNPs) but this paper emphasized their differences regarding biochemical and transcriptomic salt stress responses. Five candidate genes, two putative poplar homologues of GRAS family TFs (PtGRAS17 and PtGRAS16), PtDREB2 of DREB family TFs and two abiotic stress-inducible genes (PtP5SC1, PtSOS1), were examined for their expression profiles. Results show that most salt stress-responsive genes were induced in clones M1 and PE19/66, thus showing they can tolerate salt environments with high concentrations and could be efficient in phytoremediation of salt environments. Clone M1 and PE19/66 has ABA-dependent mechanisms expressing the PtP5CS1 gene while clone 182/81 could regulate the expression of the same gene by ABA-independent pathway. To improve salt tolerance in poplar, two putative GRAS/SCL TFs and PtDREB2 gene seem to be promising candidates for genetic engineering of salt-tolerant poplar clones.

English

Secondary metabolites are bioactive compounds which are synthesized naturally in all plant parts. The quality and quantity of secondary metabolites produced by plants differ depending on the plant and environmental conditions under which they are produced. The purpose of the study was to investigate the effects of nitrogen, phosphorous and potassium (NPK) fertilizer (17:17:17) rates (0, 100, 200, 300 and 400 kg ha-1) on the production of secondary metabolites in field and greenhouse grown pepino melons (Solanum muricatum Aiton). The experimental design was randomized complete block design with five NPK fertilizer treatments replicated three times. Results indicated that an increase in NPK fertilizer rate led to an increase of carotenoids (lutein, lycopene and β-carotene) up to a maximum at 200 kg NPK ha-1 after which the contents decreased in both growing environments and trials. The control (no fertilizer application) favored the accumulation of total phenolic content (TPC) in both growing environments and trials. Greenhouse grown pepino melon fruits which were not supplied with fertilizer (control) had a TPC content of 174.3 and 145.5 mg GAE 100g-1 fresh weight (FW) in trial one and two, respectively. Fertilizers could not enhance production of TPC in pepino melon fruits and application of 200 kg NPK ha-1 is recommended for maximum accumulation of carotenoids (lycopene, lutein and β-carotene).  Key words: Secondary metabolites, NPK fertilizer, greenhouse, field, pepino.

Salinity-Induced Physiological Responses of Three Putative Salt Tolerant Citrus Rootstocks

Our study aimed to evaluate the physiological responses following salinity treatment of three putatively salt-tolerant Citrus rootstocks recently developed by the University of Florida’s Citrus breeding program. Four-month-old seedlings from each of the three rootstocks (HS1, HS17, and HC15) were irrigated with 0, 60, 80, and 100 mm NaCl solution. The seedlings were evaluated together with the salt-tolerant Cleopatra mandarin as a positive control, Volkamer lemon as a moderately salt-tolerant rootstock, and the salt-sensitive Carrizo rootstock as a negative control. Our results demonstrated that chlorophyll content, net CO2 assimilation rate (A), transpiration rate (E), and stomatal conductance (gsw) significantly decreased in response to salinity. Na+ and Cl− levels were higher in leaf tissues than in the roots. Relatively little damage to the cellular membrane was recorded in HC15 and Cleopatra rootstocks under the 100 mm NaCl treatment, along with high accumulation of total phenolic content (TPC), while HS17 had the highest proline levels. Our results indicate that HC15 and HS17 rootstocks exhibited salt tolerance capacity via different strategies under salt stress and could be suitable replacements to the commercially available, salt-tolerant Cleopatra rootstock.

Effect of exogenous methyl jasmonate treatment on disease resistance of postharvest kiwifruit

Kiwifruit (Actinidia deliciosa cv. Jinkui) were treated with 0.1 mmol/L methyl jasmonate (MeJA) to investigate the effects on disease resistance to soft rot caused by Botryosphaeria dothidea. The results showed that MeJA treatment significantly reduced the diameter of lesions after inoculation with B. dothidea. This treatment significantly enhanced the activities of related antioxidant protective enzymes, defence-related enzymes including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), polyphenol oxidase (PPO), chitinase (CHI), β-1,3 glucanase (GLU) and increased the accumulation of total phenolic content, while the degree of membrane lipid peroxidation was reduced. MeJA treatment effectively enhanced gene expression of AcPOD, AcSOD, AcCHI and AcGLU. The results from this research suggest that MeJA treatment is a promising and safe strategy for controlling postharvest rot soft of kiwifruit.

Leaf harvesting severity affects total phenolic and tannin content of fresh and dry leaves of Moringa oleifera Lam. trees growing in Gauteng, South Africa

The most important chemicals common in Moringa oleifera Lam. leaves are polyphenols and tannins. They are synthesised during development and the amount and composition are primarily dependent on environmental conditions and factors such as leaf harvesting. Trials were conducted in the Gauteng Province at the University of Pretoria Experimental Farm on Hillcrest Campus (250 45′ 08.6″S, 280 15′ 30.S" E), with an altitude of 1372 m above sea level and an average annual rainfall of 640 mm. Five year old M. oleifera tree orchard were used for this study and treatments were laid in a randomised complete block design, where 12 plants were used in each plot within a row, with a plant spacing of 2 × 2 m2. Partial harvesting was done at 25% leaf removal, while severe leaf harvesting was done at 75% leaf removal. The control trees were not harvested, but only leaf (mature and immature) samples were harvested for analyses. Leaf samples from all plots were harvested in September, November, February and May in years 1 and 2. Leaf samples (equal quantities of immature and mature leaves) from partially, severely harvested and control plots were harvested and separated into batches, one to be analysed as fresh material and the other as dry material. The dry material was placed in paper bags and allowed to immediately air dry under normal room conditions of 26 °C. Partially harvested M. oleifera leaves produced an increased accumulation of total phenolic content (TPC) 35–44 g/kg dry weight, from spring to summer season, in comparison to severe harvesting 26–35 g/kg dry weight. With severe leaf harvesting (75%), because of probable lower photosynthetic capacity, phenols across September to May of years 1 and 2 decreased. The onset of low temperatures in May resulted mostly higher TPC and tannin build up, which means that cold stress may improve more bio-active compounds in the leaves. Dark and fully developed mature leaves mainly contained the highest amount of TPC. Moringa oleifera leaves collected and dried at each harvesting interval, instead of freshly milled, do show the same quantity of TPC and tannins across the season illustrating that air drying can be used as a post-harvest handling technique, extending shelf life without losses of vital phenols. With harvesting severity as a concern in Moringa, this study confirms that the TPC and tannins in mature and immature leaves did not rise to toxic levels for human consumption.

Identification of romaine lettuce (Lactuca sativa var. longifolia) Cultivars with reduced browning discoloration for fresh-cut processing

Discoloration (browning) represents a major challenge that limits the quality and shelf life of fresh-cut lettuce. In this study, we aimed to find romaine lettuce (Lactuca sativa var. longifolia) accessions with low browning potential. Midribs of 14 accessions (11 cultivars, two breeding lines, and a single plant introduction) were shredded and packaged in perforated bags for five days. Images of processed samples were captured daily and analyzed with computer vision technology to quantify browning intensity via L*a*b* color values and browning index (BI). Enzymatic activity[phenylalanine lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO)] and total phenolic content (TPC) were measured daily. After five days in storage, the accessions in the Tall Guzmaine and Parris Island Cos pedigree groups exhibited the greatest and least browning, respectively. In addition, while the PAL, POD, and TPC increased substantially over time, the PPO of twelve accessions fluctuated with only minor increases. For all accessions, the temporal increase of PAL, POD, and TPC showed significant, positive correlation to browning progression. Comparing between accessions, those that had greater amounts of accumulated PAL and smaller amounts of POD tended to have a greater amount of browning after five days of storage, despite relatively low correlation coefficients. However, the accumulation of TPC and PPO was not correlated to browning severity after five days of storage. This systematic study provides lettuce growers and breeders with guidance for selecting accessions with limited browning, and it supplies researchers in plant physiology and genetics with more information on the roles of enzymes in the lettuce browning process.

Effects of selenium on enzymatic changes and productivity of garlic under salinity stress

There is a lack of information pertaining to garlic growth under increasing levels of salinity. This research was conducted to assess the effects of NaCl level on growth, lipid peroxidation and antioxidant activity of marketable garlic (Allium sativum L.) in a hydroponic greenhouse experiment. Garlic plants were treated with NaCl (0, 30, 60 and 90 mM) and Na2SeO4 (0, 4, 8 and 16 mg Se L−1). The results showed that selenium application without salinity significantly increased the fresh and dry weights of bulb, number of clove per bulb, bulb diameter and bulb height compared to the control plants. Also, salt stress (30 mM) without selenium caused a drastic increase in garlic fresh and dry weights of root and bulb, bulb diameter and bulb height. Exogenous Se supply at 8 and 16 mg L−1 significantly increased Chl “a” under levels 60 mM of salinity. Also, Se supplementation at 16 mg L−1 in combination with salt stress (30 and 60 mM NaCl) significantly increased Chl “b” and total Chl. However, application of Se significantly decreased the level of malondialdehyde. Se supply (8 mg L−1) at 30 mM NaCl significantly decreased the electrolyte leakage by 58%. Low Se supply (4, 8 mg L−1) induced accumulation of total phenolic content at 90 mM NaCl, but this diminished at higher supply. The results show that garlic plants have high antioxidant activity against salinity stress without treatment with selenium compared to treated. Under salinity conditions of 30 mM NaCl, the superoxide dismutase and catalase activities increased with increasing the level of Se treatment. Addition of Se at 16 mg L−1 in combination with salt stress (60, 90 mM NaCl) significantly increased the level of ascorbate peroxidase activity. These results indicated that salt stress had a positive physiological effect on some growth parameters of garlic which is in contrast to previous reports. In addition, application of Se made garlic plants more tolerant to salt stress-induced oxidative damage by enhancing their antioxidant defense systems.

Soil constituents influence accumulation of phytochemicals and nutritional content in Wrightia tinctoria of North Gujarat, India

Wrightia tinctoria R.Br (family Apocynaceae) is a lesser known plant species used in indigenous system of medicine and dietary proposes in North Gujarat, India. The variation in nutritional and phytochemical attributes of W. tinctoria in different forest localities from North Gujarat aiming the possible effect of onsite soil factors on phytochemical and nutrients level of the species was studied. A significant level of variations in phytochemical, nutritional content and antioxidant activity was observed among localities and plant parts. Leaves exhibited higher levels of total phenolic, flavonoid, flavonol, saponin and protein content, while total alkaloid content was highest in fruits. Soil phosphorus showed negative relationship with total phenolic (p < 0.01) and flavonol (p < 0.05) in leaves and positive with protein in stem bark (p < 0.01). Saponin in leaves was significantly correlated (p < 0.05) with total soil nitrogen and carbon. The results indicate the potential role of soil constituents in accumulation of total phenolic content, total flavonoid content and antioxidant activity in above ground systems of W. tinctoria.

Elicitation of antioxidant secondary metabolites with jasmonates and gibberellic acid in cell suspension cultures of Artemisia absinthium L.

Artemisia absinthium L. is a very important species with worldwide traditional medicinal uses. In this study, effects of different concentrations of two important elicitors, methyl jasmonate (MeJA) and jasmonic acid (JA), and a phytohormone gibberellic acid (GA) on growth kinetics, secondary metabolites accumulation and antioxidant activity in cell suspension cultures of Artemisia absinthium L. were investigated. The results showed inhibition in dry biomass accumulation and shorter log phases of cultures growth in response to most treatments, compared to control. Further, we observed enhanced accumulation of total phenolic content (TPC), total flavonoid content (TFC) and highest radical scavenging activity (RSA) in suspension cultures treated with 1.0 mg/l of MeJA, JA and GA, each. The correlation studies between secondary metabolites and antioxidant activity showed TPC-dependent RSA in most cultures. MeJA and JA treated cultures showed no significant variation in the context of total flavonoid contents and 1.0 mg/l of both displayed significantly comparable maximum RSA profiles on day-24 of culture. GA-treated cultures showed minimum accumulation of TPC, but TFC and RSA were found to be significantly comparable to those in MeJA and JA treated cultures. The results showed elicitors-induced enhancement in phenolic and flavonoid accumulation and antioxidant activity in suspension cultures of Artemisia absinthium L.

Synergistic Effects of Drought Stress and Photoperiods on Phenology and Secondary Metabolism of Silybum marianum

Silybum marianum is an important medicinal plant of the family Asteraceae, well known for its set of bioactive isomeric mixture of secondary metabolites "silymarin", primarily acting as a hepato-protective agent. Abiotic stress augments plant secondary metabolism in different plant tissues to withstand harsh environmental fluctuations. In the current study, our aim was to induce drought stress in vitro on S. marianum under the influence of different photoperiod treatments to study the effects, with respect to variations in secondary metabolic profile and plant growth and development. S. marianum was extremely vulnerable to different levels of mannitol-induced drought stress. Water deficiency inhibited root induction completely and retarded plant growth was observed; however, phytochemical analysis revealed enhanced accumulation of total phenolic content (TPC), total flavonoid content (TFC), and total protein content along with several antioxidative enzymes. Secondary metabolic content was positively regulated with increasing degree of drought stress. A dependent correlation of seed germination frequency at mild drought stress and antioxidative activities was established with 2 weeks dark + 2 weeks 16/8 h photoperiod treatment, respectively, whereas a positive correlation existed for TPC and TFC when 4 weeks 16/8 h photoperiod treatment was applied. The effects of drought stress are discussed in relation to phenology, seed germination frequency, biomass build up, antioxidative potential, and secondary metabolites accumulation.

Trichoderma harzianumelicits induced resistance in sunflower challenged byRhizoctonia solani

To investigate the efficacy of Trichoderma harzianum NBRI-1055 (denoted as 'T-1055') in suppression of seedling blight of sunflower caused by Rhizoctonia solani Kühn and their impact on host defence responses. T-1055 was applied as seed treatment, soil application and combined application (seed treatment+soil application). Higher protection afforded by combined application of T-1055 was associated with the marked induction of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (PO) and cinnamyl alcohol dehydrogenase (CAD) activities. The activities of PAL and PPO reached maximum at 10days after sowing (DAS), while PO and CAD levels reached maximum at 12 DAS. This was further supported by the accumulation of total phenolic content that showed an increase up to threefold at 14 DAS. In addition, HPLC analysis revealed that the contents of ferulic and p-coumaric acids increased by 6·3 and 4·6 times, respectively, at 14 DAS. Amount of gallic acid was also little more than double. Lignin deposition in sunflower root increased by 2·7, 3·4 and 3·7 times through combined application of T-1055 at 16, 18 and 20 DAS, respectively. Combined application also increased the accumulation of PR-2 and PR-3 proteins by 3·3 and 3·9 times, respectively, at 12 DAS in followed by seed treatment alone. The combined application of T-1055 triggered defence responses in an enhanced level in sunflower than the soil and seed alone and provided better protection against Rhizoctonia seedling blight. Rhizospheric fungal bioagent 'T-1055' can enhance protection in sunflower against the R.solani pathogen through augmented elicitation of host defence responses.