Alterations in osmoregulation, antioxidant enzymes and indole alkaloid levels in Catharanthus roseus exposed to water deficit

Catharanthus roseus (L.) G. Don plants were grown in different water regimes in order to study the drought induced osmotic stress and proline (PRO) metabolism, antioxidative enzyme activities and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress from 30 days after sowing (DAS) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). The drought stressed plants showed increased aminoacid (AA), glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) and increased γ-glutamyl kinase (γ-GK) activities when compared to control. The antioxidative enzymes like peroxidase (POX) and polyphenol oxidase (PPO) increased to a significant level in drought stressed plants when compared to control. The drought stressed C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to well-watered control plants. Our results suggest that the cultivation of medicinal plants like C. roseus in water deficit areas would increase its PRO metabolism, osmoregulation, defense system and the level of active principles.     

Water deficit stress mitigation by calcium chloride in Catharanthus roseus: effects on oxidative stress, proline metabolism and indole alkaloid accumulation

The present investigation was conducted to determine whether CaCl(2) increases Catharanthus roseus drought tolerance and if such tolerance is correlated with changes in oxidative stress, osmoregulation and indole alkaloid accumulation. C. roseus plants were grown under water deficit environments with or without CaCl(2). Drought induced oxidative stress was measured in terms of lipid peroxidation (LPO) and H(2)O(2) contents, osmolyte concentration, proline (PRO) metabolizing enzymes and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with 5mM CaCl(2) and 5mM CaCl(2) alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stressed plants showed increased LPO, H(2)O(2), glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) activity and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. Addition of CaCl(2) to drought stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the gamma-GK activities. Calcium ions increased the GB contents. CaCl(2) appears to confer greater osmoprotection by the additive role with drought in GB accumulation. The drought with CaCl(2)-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to drought stressed and well-watered plants.     

Changes in antioxidant metabolism of Vigna unguiculata (L.) Walp. by propiconazole under water deficit stress

In the present study, a pot culture experiment was conducted to estimate the ameliorating effect of propiconazole (PCZ) on drought stress in cowpea (Vigna unguiculata (L.) Walp.) plants. From 30 days after sowing (DAS), the plants were subjected to 3, 6 and 9 days interval drought (DID) stress and drought stress with PCZ at 15 and 15 mg l(-1) PCZ alone and 1 day interval irrigation was kept as control. The plant samples were collected on 34 DAS (3 DID), 37 DAS (6 DID) and 40 DAS (9 DID). The plants were separated into root, stem and leaf for estimating the antioxidant contents and activities of antioxidant enzymes. Individual and combined drought stress and PCZ treatments increased ascorbic acid (AA), alpha-tocopherol (alpha-toc) contents, superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and polyphenol oxidase (PPO) activities when compared to control. The PCZ treatment mitigated the adverse effects of drought stress by increasing the antioxidant potentials and thereby paved the way for overcoming drought stress in V. unguiculata plants.     

Antioxidant potential and indole alkaloid profile variations with water deficits along different parts of two varieties of Catharanthus roseus

The variations in antioxidant potentials and indole alkaloid content were studied in the present investigation, in two varieties (rosea and alba) of Catharanthus roseus, an important herb used in traditional as well as modern medicine, exposed to water deficit stress. The antioxidant and alkaloid profiles were estimated from root, stem, leaf, flowers and pods. The antioxidant potentials were examined in terms of non-enzymatic antioxidant molecules and activities of antioxidant enzymes. The non-enzymatic antioxidant molecules studied were ascorbic acid (AA), -tocopherol (-toc) and reduced glutathione (GSH). The estimated antioxidant enzymes were superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO). The antioxidant concentrations and activities of antioxidant enzymes were high under water deficit stress in all parts of the plants. Indole alkaloid content was high in the roots of rosea variety in response to stress when compared to alba variety.     

Protection of Vigna unguiculata (L.) Walp. plants from salt stress by paclobutrazol

A pot culture experiment was conducted to estimate the stress ameliorating ability of paclobutrazol, a triazole fungicide in Vigna unguiculata (L.) Walp. plants. Treatments were given as 80 mM NaCl, 80 mM NaCl + 15 mg l⁻¹ paclobutrazol and 15 mg l⁻¹ paclobutrazol alone. The samples were collected on 60 and 80 days after sowing (DAS). NaCl stress inhibited the root and stem length, total leaf area, fresh weight (FW), dry weight (DW) and activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX). Plants treated with NaCl with paclobutrazol increased these parameters to a larger extent when compared to NaCl stressed plants. The results showed that the paclobutrazol significantly ameliorated the adverse effects of NaCl stress in V. unguiculata plants.     

Pseudomonas fluorescens enhances biomass yield and ajmalicine production in Catharanthus roseus under water deficit stress

The effect of plant growth promoting rhizobacteria (PGPR) like Pseudomonas fluorescens on growth parameters and the production of ajmalicine were investigated in Catharanthus roseus under drought stress. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with Pseudomonas fluorescens at 1mgl(-1) and 1mgl(-1)Pseudomonas fluorescens alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stress decreased the growth parameters and increased the ajmalicine content. But the treatment with Pseudomonas fluorescens enhanced the growth parameters under drought stress and partially ameliorated the drought induced growth inhibition by increasing the fresh and dry weights significantly. The ajmalicine content was again increased due to Pseudomonas fluorescens treatment to the drought stressed plants. From the results of this investigation, it can be concluded that, the seedling treatments of native PGPRs can be used as a good tool in the enhancement of biomass yield and alkaloid contents in medicinal plants, as it provides an eco-friendly approach and can be used as an agent in water deficit stress amelioration.     

Water deficit stress effects on reactive oxygen metabolism in Catharanthus roseus; impacts on ajmalicine accumulation

In the present work, we have analysed the changes in the reactive oxygen metabolism of Catharanthus roseus (L.) G. Don. plants in terms of H(2)O(2) content, lipid peroxidation and the free radical quenching systems (non-enzymatic and enzymatic antioxidants) under drought stress. In addition to this, the root alkaloid ajmalicine was extracted and quantified from both control and drought stressed plants. The H(2)O(2) content was analysed from both stressed and unstressed control plants. Lipid peroxidation was estimated as thiobarbituric acid reactive substances. The non-enzymatic antioxidants viz., ascorbic acid, alpha-tocopherol and reduced glutathione contents, antioxidant enzymes like superoxide dismutase, ascorbate peroxidase, and catalase were extracted and estimated from the samples. The alkaloid ajmalicine was extracted and quantified from shade dried root samples and found significantly increased over control. From the results of this investigation, it can be concluded that the water deficit areas may be well used for the cultivation of medicinal plants like C. roseus and the economically important alkaloid production can be enhanced in the plant level.     

Comparative effects of different triazole compounds on antioxidant metabolism of Solenostemon rotundifolius

The effect of different triazole compounds, viz., triadimefon (TDM) and hexaconazole (HEX) treatments on the antioxidant metabolism of Solenostemon rotundifolius Poir., Morton plants was investigated in the present study under pot culture. Plants were treated with TDM at 15 mg l⁻¹ and HEX at 10 mg l⁻¹ separately by soil drenching on 80, 110 and 140 days after planting (DAP). The plants were harvested randomly on 90, 120 and 150 DAP for determining the effect of both the triazoles on non-enzymatic antioxidant contents like ascorbic acid (AA), reduced glutathione (GSH) and -tocopherol (-toc), activities of antioxidant enzymes like superoxide dismutase (SOD) and ascorbate peroxidase (APX). All the analyses were made in leaf, stem and tubers of both control and treated plants. It was found that both these triazole compounds have profound effects on the antioxidant metabolism and caused an enhancement in both non-enzymatic and enzymatic antioxidant potentials under treatments. These results suggest that, the application of triazoles may be a useful tool to increase the antioxidant production in S. rotundifolius and thereby make it an economical food crop.     

Effect of paclobutrazol on water stress amelioration through antioxidants and free radical scavenging enzymes in Arachis hypogaea L

An investigation was carried out to find out the extent of changes occurred in groundnut (Arachis hypogaea L.) cultivars in response to paclobutrazol (PBZ) treatment under water deficit stress. Two groundnut cultivars namely ICG 221 and ICG 476 were used for the study. Individual treatment with PBZ and drought stress showed an increase in ascorbic acid, -tocopherol and reduced glutathione, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities. PBZ with drought stressed plants maintained higher levels of antioxidant and scavenging enzymes. Significant differences were observed between cultivars and treatments. These results suggests that the adverse effects of water stress can be minimized by the application of PBZ by increasing the antioxidant levels and activities of scavenging enzymes such as SOD, APX and CAT. The Cv. ICG 221 appears to be more tolerant to water stress than the ICG 476.     

Alterations in morphological parameters and photosynthetic pigment responses of Catharanthus roseus under soil water deficits

An experiment was conducted in two varieties, rosea and alba, of Catharanthus roseus plants with two watering treatments viz., 100 and 60% of field capacity, to understand the effects of water deficit on early growth, biomass allocation and photosynthetic pigment responses. We found that there were significant differences in early growth, dry matter accumulation and pigment variations between the two varieties. The root length, shoot length, total leaf area, fresh and dry weights were significantly reduced under water stress treatments. There was a significant reduction in the photosynthetic pigment contents in both the varieties. The rosea variety was more affected due to water deficit when compared to alba variety.     

Effect of sound wave stress on antioxidant enzyme activities and lipid peroxidation of Dendrobium candidum

The effect of sound wave stress on important medicinal plant, Dendrobium candidum Wall. ex Lindl, was investigated, including the responses on malondialdehyde (MDA) content, the activities change of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX). Results were found that the activities of SOD, CAT, POD and APX enhanced totally in different organs of D. candidum, as leaves, stems and roots, in response to the stress. Furthermore there happened similar shift of antioxidant enzymes activities, which increased in the initial stimulation and decreased afterwards. Data showed SOD, CAT, POD and APX activities ascended to max at day 9, 6, 9 and 12 in leaves, at day 9, 6, 12 and 9 in stems, and at day 12, 6, 9 and 9 in roots, respectively. As a lipid peroxidation parameter, MDA content in different organs increased in the beginning, dropped afterward, and increased again in the late. Anyway the total trend was the rise of MDA level compared to the control. It was interesting that the MDA content appeared the lowest levels almost when the antioxidant enzymes activities were up to the highest. Our results demonstrated the different organs of D. candidum might produce accumulation of active oxygen species (AOS) under initial treatment of sound wave stress. Later AOS might start to reduce due to the enhancement of antioxidant enzymes activities treated by the stress. The data revealed that the antioxidant metabolism was to be important in determining the ability of plants to survive in sound stress, and the up regulation of these enzymes activities would help to reduce the build up of AOS, which could protect plant cells from oxidative damage. Moreover, different cell compartments might activate different defensive system to reduce excessive amount of AOS. Finally the mechanism of this action was also discussed simply.     

Effects of Vitamin E on the Activities of Protective Enzymes and Membrane Lipid Peroxidation in Leymus Chinensis under Drought Stress

Leymus chinensis seedlings were treated with 0.05--10 mmol/L vitamin E under osmotic stress in the presence of polyethylene glycol（PEG） as the stress reagent. The effects of the different concentrations of exogenous vitamin E on the activities of SOD, POD and free proline, and the MDA contents under drought stress were examined so as to ascertain the mechanism of Leymus chinensis resistance to drought stress and explore the possible preventive measures. The results indicate that the activities of SOD and POD decreased but the free proline and MDA contents increased as drought stress was accentuated, showing an enhancement of oxidative stress that may cause a decline in membrane stabilization. However, the activities of SOD and POD and the free proline content increased, whereas the MDA content reduced in Leymus chinensis pretreated with vitamin E in comparison with that of the control. This indicates that exogenous vitamin E enhanced the antioxidation of Leymus chinensis seedlings. It suggests that cytomembrane can be protected from damage by increasing the free proline content and the activities of SOD and POD that result in enhancing the drought resistance of Leymus chinensis seedlings.     

Differential effects of hexaconazole and paclobutrazol on biomass, electrolyte leakage, lipid peroxidation and antioxidant potential of Daucus carota L

The application of triazole fungicides is a common practice in the cultivation of carrot (Daucus carota L.) plants. It is there for seems important to test the changes that are occurring in this food crop under triazoles, the non-traditional plant growth regulators, treatments in order to identify the extent to which it tolerate the fungicide application and thereby make it an economical food crop. A field experiment was conducted to find out the effects of two triazole fungicides (hexaconazole (HEX) and paclobutrazol (PBZ) at 20 mg l⁻¹ plant⁻¹) on the biomass, yield, electrolyte leakage, lipid peroxidation and antioxidant potential of carrot. The treatments were given to plants on 15, 30 and 45 days after sowing (DAS). The plants were uprooted for analyses of growth and biochemical parameters on 60 DAS. It was found that both HEX and PBZ have significant effects on the growth and biochemical parameters of this plant. Among the triazoles used, PBZ performed best in terms of anthocyanin, protein, amino acid, proline, starch and sugar, contents whereas HEX enhanced carotenoids, fresh weight, dry weight and biomass. There was no significant variation in chlorophyll (‘a’ and ‘b’) contents between the two triazole treated plants, but HEX and PBZ proved best when compared to untreated control plants. HEX and PBZ increased - and β-amylases enzymes activities to a significant level. Out of these two triazoles, PBZ performed best in increasing the starch hydrolyzing enzymes activities. The non-enzymatic antioxidant, reduced glutathione (GSH) and antioxidant enzyme ascorbate peroxidase (APX) were increased under fungicide applications. The data suggests that, the application of triazole fungicides may be a useful tool to increase the tuber quality as well as quantity in carrot plants, apart from their fungicidal properties.     

Antioxidant potentials and ajmalicine accumulation in Catharanthus roseus after treatment with giberellic acid

Changes in antioxidant potentials and indole alkaloid, ajmalicine, production were studied in Catharanthus roseus (L.) G. Don. plants under treatment with gibberellic acid (GA(3)). The GA(3) treatments were given in two ways, foliar spray and soil drenching methods on 30, 45, 60 and 75 days after planting (DAP). The plants were uprooted randomly on 90 DAP and separated into root, stem and leaves and used for analyses. The antioxidant potential was studied in terms of non-enzymatc antioxidant molecules like ascorbic acid (AA), alpha-tocopherol (alpha-toc) and reduced glutathione (GSH) and activities of antioxidant enzyme, viz., superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT). The alkaloid ajmalicine was extracted and estimated from roots of both control and treated plants. It was found that, GA(3) has a profound effect upon the antioxidant potentials and it caused a significant enhancement in the production of ajmalicine when compared to untreated control as well as foliar-sprayed plants. There was no significant enhancement in GSH and ajmalicine content under GA(3) foliar spray in C. roseus. These preliminary results suggest that, the application of GA(3) may be a useful tool to increase the antioxidant potential and alkaloid production in medicinal plants like C. roseus.     

Endophytic Fungi Produce Gibberellins and Indoleacetic Acid and Promotes Host-Plant Growth during Stress

We isolated and examined two endophytic fungi for their potential to secrete phytohormones viz. gibberellins (GAs) and indoleacetic acid (IAA) and mitigate abiotic stresses like salinity and drought. The endophytic fungi Phoma glomerata LWL2 and Penicillium sp. LWL3 significantly promoted the shoot and allied growth attributes of GAs-deficient dwarf mutant Waito-C and Dongjin-beyo rice. Analysis of the pure cultures of these endophytic fungi showed biologically active GAs (GA₁, GA₃, GA₄ and GA₇) in various quantities. The cultures of P. glomerata and Penicillium sp. also contained IAA. The culture application and endophytic-association with host-cucumber plants significantly increased the plant biomass and related growth parameters under sodium chloride and polyethylene glycol induced salinity and drought stress as compared to control plants. The endophytic symbiosis resulted in significantly higher assimilation of essential nutrients like potassium, calcium and magnesium as compared to control plants during salinity stress. Endophytic-association reduced the sodium toxicity and promoted the host-benefit ratio in cucumber plants as compared to non-inoculated control plants. The symbiotic-association mitigated stress by compromising the activities of reduced glutathione, catalase, peroxidase and polyphenol oxidase. Under stress conditions, the endophyte-infection significantly modulated stress through down-regulated abscisic acid, altered jasmonic acid, and elevated salicylic acid contents as compared to control. In conclusion, the two endophytes significantly reprogrammed the growth of host plants during stress conditions.     

Expression Profiling of Flavonoid Biosynthesis Genes and Secondary Metabolites Accumulation in Populus under Drought Stress

Flavonoids are key secondary metabolites that are biologically active and perform diverse functions in plants such as stress defense against abiotic and biotic stress. In addition to its importance, no comprehensive information has been available about the secondary metabolic response of Populus tree, especially the genes that encode key enzymes involved in flavonoid biosynthesis under drought stress. In this study, the quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the expression of flavonoid biosynthesis genes (PtPAL, Pt4-CL, PtCHS, PtFLS-1, PtF3H, PtDFR, and PtANS) gradually increased in the leaves of hybrid poplar (P. tremula × P. alba), corresponding to the drought stress duration. In addition, the activity and capacity of antioxidants have also increased, which is positively correlated with the increment of phenolic, flavonoid, anthocyanin, and carotenoid compounds under drought stress. As the drought stress prolonged, the level of reactive oxygen species such as hydrogen peroxide (H₂O₂) and singlet oxygen (O₂⁻) too increased. The concentration of phytohormone salicylic acid (SA) also increased significantly in the stressed poplar leaves. Our research concluded that drought stress significantly induced the expression of flavonoid biosynthesis genes in hybrid poplar plants and enhanced the accumulation of phenolic and flavonoid compounds with resilient antioxidant activity.     

Comparative effects of different triazole compounds on growth, photosynthetic pigments and carbohydrate metabolism of Solenostemon rotundifolius

The effects of two triazole compounds, triadimefon and hexaconazole, on the growth and carbohydrate metabolism were studied in Solenostemon rotundifolius Poir., Morton plants under pot culture. Plants were treated with triadimefon at 15mg l(-1) and hexaconazole at 10mg l(-1) separately by soil drenching on 80, 110 and 140 days after planting (DAP). The plants were harvested randomly and growth parameters were studied on 90, 120 and 150 DAP for determining the effect of both the triazole on growth and chlorophyll pigments. These triazole compounds increased the chlorophyll pigments. However, both the treatments decreased the fresh and dry weights of shoot and leaf area. Both these triazole resulted in a marginal increase in starch content and decreased the sugar contents. The carbohydrate metabolizing enzymes alpha- and beta-amylase activities were reduced and invertase activity increased in S. rotundifolius under triadimefon and hexaconazole treatments.     

Soil applied cobalt alters the nodulation, leg-haemoglobin content and antioxidant status of Glycine max (L.) Merr

The present investigation has been carried out to estimate the effect of cobalt on the nodulation leg-haemoglobin content and antioxidant enzyme activities of soybean plants. The experiments were conducted in earthen pots containing 3 kg of air dried soil. The inner surface of pots was lined with polythene sheet. Soybean plants were raised in soil amended with different concentration of cobalt (0, 50, 100, 150, 200 and 250 mg/kg). The root nodule formation, leg-haemoglobin contents and antioxidant enzyme activities were analysed at 15 days intervals, namely 15, 30, 45, 60 and 75 days after sowing (DAS). There found a significant increase in the total number of root nodules, leg-haemoglobin content and antioxidant enzyme activities at 50 mg/kg cobalt application in the soil in all the sampling days when compared to control. Further increase in the cobalt level (100–250 mg/kg) in the soil decreased root nodules formation as well as leg-haemoglobin content antioxidant enzyme activities of soybean plants in all the sampling days.     

Growth, biochemical modifications and proline metabolism in Helianthus annuus L. as induced by drought stress

In the present investigation, two watering treatments, viz., 100% and 60% field capacity (FC) were used to understand the effects of water deficit on early growth, biomass allocation, pigment and biochemical constituents and proline metabolism of five varieties of Sunflower (Helianthus annuus L.) plants. We found that there was a significant difference in early growth, dry matter accumulation, pigment, biochemical constituents and proline metabolism among the five varieties. The root length, shoot length, total leaf area, fresh and dry weight, chlorophyll a, b, total chlorophyll and carotenoid were significantly reduced under water stress treatments. Water stress increased the proline, free amino acid and glycinebetaine contents along with increased activity of γ-glutamyl kinase but the activity of proline oxidase reduced as a consequence of water stress.     

Impact of Peels Extracts from an Italian Ancient Tomato Variety Grown under Drought Stress Conditions on Vascular Related Dysfunction

Background: Tomato by-products contain a great variety of biologically active substances and represent a significant source of natural antioxidant supplements of the human diet. The aim of the work was to compare the antioxidant properties of a by-product from an ancient Tuscan tomato variety, Rosso di Pitigliano (RED), obtained by growing plants in normal conditions (-Ctr) or in drought stress conditions (-Ds) for their beneficial effects on vascular related dysfunction. Methods: The antioxidant activity and total polyphenol content (TPC) were measured. The identification of bioactive compounds of tomato peel was performed by HPLC. HUVEC were pre-treated with different TPC of RED-Ctr or RED-Ds, then stressed with H₂O₂. Cell viability, ROS production and CAT, SOD and GPx activities were evaluated. Permeation of antioxidant molecules contained in RED across excised rat intestine was also studied. Results: RED-Ds tomato peel extract possessed higher TPC than compared to RED-Ctr (361.32 ± 7.204 mg vs. 152.46 ± 1.568 mg GAE/100 g fresh weight). All extracts were non-cytotoxic. Two hour pre-treatment with 5 µg GAE/mL from RED-Ctr or RED-Ds showed protection from H₂O₂-induced oxidative stress and significantly reduced ROS production raising SOD and CAT activity (* p < 0.05 and ** p < 0.005 vs. H₂O₂, respectively). The permeation of antioxidant molecules contained in RED-Ctr or RED-Ds across excised rat intestine was high with non-significant difference between the two RED types (41.9 ± 9.6% vs. 26.6 ± 7.8%). Conclusions: RED-Ds tomato peel extract represents a good source of bioactive molecules, which protects HUVECs from oxidative stress at low concentration.