Responses of antioxidant defense system of <Emphasis Type="Italic">Catharanthus roseus</Emphasis> (L.) G. Don. to paclobutrazol treatment under salinity

The effect of paclobutrazol, a plant growth regulator, on antioxidant defense system was investigated in Catharanthus roseus (L.) G. Don. plants subjected to NaCl stress. The growth parameters were significantly reduced under 80 mM NaCl treatment; however, this growth inhibition was less in paclobutrazol-treated (15 mg l⁻¹ plant⁻¹) plants. The non-enzymatic antioxidants ascorbic acid and reduced glutathione were affected under NaCl stress and they increased significantly under paclobutrazol treatment when compared to NaCl treated as well as control plants (P ≤ 0.05). The activity of antioxidant enzyme ascorbate peroxidase showed a significant enhancement under salinity stress. The catalase activity decreased in roots of NaCl-treated plants, but recovered with paclobutrazol treatment. The results suggested that paclobutrazol have significant role in contributing salt stress tolerance of C. roseus by improving the components of antioxidant defense system.     

Traditional and non-traditional plant growth regulators alters phytochemical constituents in Catharanthus roseus

The effect of different plant growth regulators (PGR) and elicitor treatments on the alkaloid profile variation of Catharanthus roseus was investigated in the present study. The PGR used were paclobutrazol (PBZ), gibberellic acid (GA₃) and Pseudomonas fluorescens elicitors (PF Elicitors). The estimated alkaloids were ajmalicine, catharanthine, tabersonine, serpentine and vindoline. In roots, the ajmalicine content increased significantly under all the treatments on all sampling days. In roots, the catharanthine contents increased with the age in control and growth regulator treatments, but the increase was not prominent and significant in PGR treatments when compared to controls. The serpentine contents of the plant increased with PGR treatments, but the increase was more prominent in PBZ treatments when compared to other treatments. The increase was in the order PBZ > PF Elicitors > GA₃. C. roseus never showed any significant increase in tabersonine contents in the roots under GA₃ treatments, but it increased significantly under PBZ and PF Elicitors when compared to control plants. The root vindoline contents increased with PBZ and PF Elicitors treatments but the decreased under GA₃ treatments when compared to control plants. Our results have good significance, as these increases the secondary metabolites of this traditional medicinal plant.     

Responses of antioxidant potentials in Dioscorea rotundata Poir. following paclobutrazol drenching

The effect of paclobutrazol (PBZ) treatments on the antioxidant metabolism of white yam (Dioscorea rotundata Poir.) was investigated in the present study. PBZ @ 15 mg l(-1) plant(-1) was given to plants by soil drenching, 30, 60, and 90 days after planting (DAP). The non-enzymatic antioxidant contents like ascorbic acid (AA), reduced glutathione (GSH) and alpha-tocopherol (alpha-toc), activities of antioxidant enzymes like superoxide dismutase (SOD), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and catalase (CAT) were extracted and assayed on 100 DAP from leaf, stem and tubers of both control and PBZ treated plants. It was found that PBZ has a profound effect on the antioxidant metabolism and caused an enhancement in both non-enzymatic and enzymatic antioxidant potentials under treatments in white yam. Our results have good significance, as this increase the innate antioxidant potential of this food crop, which is helpful to satisfy the needs of antioxidants in diet and thereby make it an economically important food crop.     

Effect of plant growth regulators on the biosynthesis of vinblastine,vindoline and catharanthine in <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

Catharanthuse roseus is a well-known medicinal plant for its two valuable anticancer compounds: vinblastine and vincristine, which belongs to terpenoid indole alkaloids. Great efforts have been made to study the principles of its secondary metabolic pathways to regulate the alkaloids biosynthesis. In this article, different plant growth regulators were shortly applied to Catharanthus roseus plants during the blooming period to study their effects on the biosynthesis of vinblastine, vindoline and catharanthine. Salicylic acid and ethylene (ethephon) treatments resulted in a significant increase of vinblastine, vindoline and catharanthine while abscisic acid and gibberellic acid had a strongly negative influence on the accumulation of the three important alkaloids. Methyl jasmonate showed no great effect on the production of these valuable alkaloids. Chlormequat chloride highly enhanced the accumulation of vinblastine but greatly decreased the contents of vindoline and catharanthine.     

Association of some plant defense enzyme activities with systemic resistance to early leaf blight and leaf spot induced in tomato plants by azoxystrobin and Pseudomonas fluorescens

Abstract

Azoxystrobin at three different concentrations, namely, 31.25, 62.50 and 125 g a.i. ha^?1 mancozeb (1 kg ha^?1) and Pseudomonas fluorescens (10 kg ha^?1) were evaluated for their efficacy in inducing defense enzymes in tomato against Alternaria solani and Septoria lycopersici. The activity of defense enzymes peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), β-1, 3 glucanase, chitinase, catalase and defense-inducing chemicals (total phenols) was found to be increased in azoxystrobin and P. fluorescens-treated tomato plants. The activity of these defense enzymes and chemicals was higher in azoxystrobin (125 g a.i. ha^?1) and P. fluorescens-treated tomato plants challenge inoculated with the pathogens compared to other treatments. Increased expression of specific isoforms of PO and PPO was also observed due to ISR induction.     

Effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the phytoremediation potential of Catharanthus roseus (L.) in Cu and Pb-contaminated soils

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the growth and phytoremediation potential of Catharanthus roseus in Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. The P. fluorescens RB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly, B. subtilis 189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation of P. fluorescens RB4, B. subtilis 189, and P. fluorescens RB4 + B. subtilis 189 resulted in higher accumulation of Cu and Pb in shoots of the C. roseus grown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability of C. roseus was improved by inoculation of P. fluorescens RB4 and B. subtilis 189.     

Hormonal effects on phyllotaxis ofEuphorbia lathyris L.

Benzyladenine and gibberellic acid sprays (100 mg/l) onEuphorbia lathyris L. plants were absolutely successful (100% of the plants) in inducing a change in its normal decussate phyllotaxis. Benzyladenine produced a change to tetracussate, tricussate and bijugate, and gibberellic acid to spiral phyllotaxis. Benzyladenine and gibberellic acid treatments resulted in a significant increase in apex diameter (72.8% and 19.1% respectively). CCC, Ancymidol, Alar and Glyphosine did not alter decussate phyllotaxis.     

Dormancy of <Emphasis Type="Italic">Nicotiana benthamiana</Emphasis> seeds can be broken by different compounds

The influence of after-ripening, sodium nitroprusside, potassium ferricyanide, cyanide, paclobutrazol and nitrite on germination of seeds of Nicotiana benthamiana was investigated as well as the influence of plant hormones such as gibberellins and abscisic acid. Dormancy of N. benthamiana seeds was broken by all treatments except treatments with abscisic acid, paclobutrazol and gibberellic acid (GA₃). Gibberellins had an interesting effect on dormancy breakage of studied seeds which was dependent on use of particular gibberellin: GA₃ or GA₄₊₇. Unlike GA₃, GA₄₊₇ had broken seed dormancy.     

Biological control of root-knot nematode (Meloidogyne javanica) disease by Pseudomonas fluorescens (Chao)

Plant growth-promoting Rhizobacteria is currently developed as an biocontrol agent against many plant pathogens. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Pseudomonas fluorescens was investigated in greenhouse and laboratory experiments. Results showed that 10⁹?(CFU/ml) of P. fluorescens decreased nematode infection and other parameters significantly, compared to the control. P. fluorescens was able to cause destruction of nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX) and phenylalanine ammonia lyase (PAL), increased significantly in P. fluorescens-inoculated plants. Maximum activities of POX and PAL were observed at the 5?days after inoculation, respectively. Results suggested that the destruction of eggs and plant defence mechanisms leading to systemic resistance are two main suppression mechanisms used by P. fluorescens against nematode.     

Sucrose application causes hormonal changes associated with potato tuber induction

Stems of potato plants (Solanum tuberosum L. cv. Dianella) were immersed in solutions containing water (control), sucrose, glucose, paclobutrazol, and gibberellic acid. The effects of these treatments on the ethylene release, levels of endogenous gibberellins, glucose, sucrose, and starch were correlated with tuberization of nodal cuttings, excised from potato stems. Paclobutrazol and sucrose improved the percent of tuberization and/or increased tuber weight. In contrast, GA₃ inhibited tuber formation compared with the control. The level of endogenous free GAs was negatively correlated with percent tuberization. However, the level of conjugated GAs was positively correlated with both percent tuberization and tuber weight. The effect of sucrose on potato tuber induction in relation to the possible role of sucrose in GA-conjugate formation is discussed.     

Interactive effects of triadimefon and salt stress on antioxidative status and ajmalicine accumulation in Catharanthus roseus

The ability of triadimefon (TDM), a triazole group of fungicide, to ameliorate salinity stress was studied in Catharanthus roseus (L.) G. Don. plants subjected to sodium chloride (NaCl) treatment. NaCl treatment at 80 mM level decreased overall growth of this plant and reduced the chlorophyll contents, protein, antioxidant enzymes such as peroxidase (POX), superoxide dismutase (SOD) and polyphenol oxidase (PPO). The root alkaloid ajmalicine got increased under salt treatment. When these stressed plants were treated with TDM at 15 mg l⁻¹ concentration minimized the inhibitory effects of NaCl stress by increasing the root, shoot growth and leaf area and increased dry weight (DW), chlorophyll, protein contents and the activities of antioxidant enzymes like POX, SOD and PPO, thereby paved the way to overcome the salinity injury. The quantity of ajmalicine was again increased with the TDM treatment when compared to both control and NaCl treated plants. From these results, it is proved that the fungicide TDM have great role in the enhancement of plant antioxidative enzymes and the enhanced scavenging of potentially harmful free radicals, as a mechanism of protecting plants against noxious oxidative stress from the environment and also in the enhancement of active principles.     

Responses of growth and antioxidant systems in <Emphasis Type="Italic">Carthamus</Emphasis><Emphasis Type="Italic">tinctorius</Emphasis> L. under water deficit stress

An investigation was carried out to find out the extent of changes occurred in two safflower (Carthamus tinctorius L.) cultivars in response to water deficit stress. Two safflower cultivars namely IL.111 and Isfahan were used for the study. Thirty days after sowing, plants were grown under soil moisture corresponding to 100, 85, 70 and 55% field capacity for next 30 days. Water deficit treatments significantly decreased the shoot length, shoot dry matter, root dry matter, relative growth rate, leaf relative water content (LRWC) and leaf water potential (Ψ_W), whereas root length, root-to-shoot ratio, lipid peroxidation and antioxidant compounds such as ascorbic acid (AA), α-tocopherol (α-Toc) and reduced glutathione (GSH) and superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), and peroxidase (POX, EC 1.11.1.7) activities were increased. Water deficit stressed plants maintained higher levels of compounds and scavenging enzymes. Significant differences were observed between cultivars and irrigation levels treatments. The cv. IL.111 could be considered more tolerant to water stress than cv. Isfahan, registering greater biomass, LRWC and leaf water potential (Ψ_W), associated with high antioxidant activity.     

Elicitation of secondary metabolism in Echinacea purpurea L. by gibberellic acid and triazoles

In vitro bioreactor production of Echinacea purpurea L. was used to facilitate the screening of compounds capable of eliciting increased secondary metabolite production. Based on previous experience with various bioreactors, the Southern Sun Liquid Lab Rocker was selected for this study as it produces healthy, vigorous, whole plants. The focus of the present study was to quantify the concentration of the medicinally important secondary metabolites caftaric acid and cichoric acid and to study the effect of growth regulators on the production of these compounds in this system. Both marker compounds were produced at levels that compared favorably to field grown plants. Application of gibberellic acid (GA₃), paclobutrazol, uniconazole and a combined treatment of GA₃ with paclobutrazol to the in vitro plants generally increased the concentration of caftaric acid in the roots with little effect on the concentration in the shoots. The concentration of cichoric acid was higher in the roots of treated plants than in the roots of control plants, but lower in corresponding shoots. The present study highlights the use of in vitro production of whole plants as a model system for studying the regulation of plant secondary metabolism in a controlled environment.     

Effect of triadimefon: a triazole fungicide on oxidative stress defense system and eugenol content in <Emphasis Type="Italic">Ocimum tenuiflorum</Emphasis> L.

The effect of triadimefon (TDM) a triazole compound on antioxidant potential and eugenol content was studied in Ocimum tenuiflorum L. The plant was subjected to 15 mg/l TDM by soil-drenching on 50th, 70th and 90th days after planting (DAP). Analyses were carried out on 60th, 80th and 100th DAP. Both enzymatic and non-enzymatic antioxidant potential estimation was carried out. The non-enzymatic antioxidant viz ascorbic acid, α-tocopherol and reduced glutathione were found to increase under triadimefon treatment. The antioxidant enzyme like superoxide dismutase, ascorbate peroxidase and catalase activities showed significant increase in TDM treatment. Triazole-treated plants yielded more eugenol (a major component of Ocimum-essential oil) in comparison to control. The study evidenced that TDM residues could be detected in the upper soil layer only and does not accumulate in the soil. These preliminary results suggest that TDM may be useful to increase the antioxidant content in medicinal plants and also to act as an elicitor to enhance the production of secondary metabolites of medicinal plants.     

Leucojum aestivum L. in vitro bulbs induction and acclimatization

The effects of growth retardants (paclobutrazol and ancymidol), sucrose, GA₃ (gibberellic acid) and physical state of the medium (solid and liquid — Rita® temporary immersion system) on in vitro induction of Leucojum aestivum bulbs and their acclimatization were studied. Paclobutrazol, regardless of the physical state of the medium, stimulated the formation of bulbs (99.3%). Under the influence 90 g L^?1 of sucrose or paclobutrazol the bulbs with the highest fresh weight (FW) were formed (250 mg and 208.8 mg, respectively). However, the addition of ancymidol to the liquid medium led to obtaining the bulbs showing the highest number of leaves and roots (63.2% and 91.7%, respectively). The scanning microscopy study proved that plants obtained in the medium containing GA₃ produced the stomata which most closely resembled to the one observed in the mother plant. Cytometric analysis of all regenerants revealed absence of changes in the nuclear DNA content. The maximum survival rate (100%) was observed for plants derived from liquid medium containing 90 g L^?1 of sucrose. Somewhat fewer plants were acclimatized after their cultivations in liquid medium enriched with paclobutrazol or ancymidol. The temporary immersion system led to perform successful ex vitro adaptation of Leucojum aestivum plants.     

Effect of drought and low light on growth and enzymatic antioxidant system of Picea asperata seedlings

The combined effects of drought and low light on biomass partition, foliar nitrogen concentration, membrane stability and active oxygen species (AOS) and antioxidant system were investigated in dragon spruce (Picea asperata Mast.) seedlings grown at two watering regimes (well-watered, 100% of field capacity and drought, 30% of field capacity) and light availabilities (HL, 100% of full sunlight and low light, 15% of full sunlight). Under high light condition drought not only reduced foliar nitrogen concentration (Nmass) and membrane stability index (MSI) but also significantly increased biomass partitioning to roots, AOS, ascorbic acid (AsA) content and antioxidant enzyme activities including superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase(GR, EC 1.6.4.2). However, no prominently drought-induced differences in biomass partitioning to root, SOD, GR activities, hydrogen peroxide (H₂O₂) and MSI were observed in low light seedlings. On the other hand, significant interaction of drought and low light was found on MSI, the antioxidant enzymes activities (SOD, POD, CAT, APX, GR), H₂O₂ and superoxide radical (O₂ ⁻). These results suggested that seedlings grown at the understory were more sensitive to drought than low light.     

Rhizobacterial bioformulation for the effective management of Macrophomina root rot in mungbean

Abstract

Fluorescent pseudomonads based bioformulation was evaluated for their ability to control Macrophomina root rot disease in mungbean (Vigna mungo). P. fluorescens isolate Pf1 showed the maximum inhibition in mycelial growth of Macrophomina phaseolina under in vitro conditions. Bioformulation of Pf1 with chitin was effective in reducing the root rot incidence in green gram both under glasshouse and field conditions. The rhizosphere colonization of P. fluorescens was observed appreciable with the green gram plants. However, Pf1 amended with chitin colonized effectively. Furthermore, the induction of defence-related enzymes and chemicals in plants by Pf1 amended with or without chitin and neem were tested. Increased accumulation of defence enzymes viz., phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), chitinase, β-1,3-glucanse and phenolics were observed in Pf1 bioformulation amended with chitin, pre-treated plants challenge inoculated with M. phaseolina under glasshouse conditions. The present study reveals that in addition to direct antagonism and plant-growth promotion, PGPR strains amended with chitin bioformulation induced defence-related enzymes and pathogenesis related (PR) proteins which collectively enhance the resistance in green gram against the infection of M. phaseolina.     

Effect of detoxified Aflatoxin B1 contaminated products on some in vivo and in vitro plant physiological systems

Aflatoxin B₁ was detoxified (60 %) enzymatically by horseradish peroxidase. In another set of experiments the toxin was detoxified (97 %) by a combination of enzyme and microwave treatments. Chloroform extracts of these reaction products were used to study their effects on some important physiological processes of higher plants. Cell mass growth in suspension culture of Catharanthus roseus showed 34 % and 77 % respective increase in dry weight after 4 to 8 weeks of incubation at room temperature (22 EC) without toxin but in presence of toxin only 21 % and 43 % dry weight increase occurred in the same time interval. Aflatoxin B₁ showed a profound effect on pollen germination and pollen tube morphology leading to only 40 % germination and several morphological anomalies in Catharanthus roseus and Haemanthus Katherinae. Embryogenic callus of Santalum album could give rise to only 60 % somatic embryo in presence of 1mM toxin with several abnormalities which is much less compared to 94 % conversion to distinct bipolar embryos in case of control set without toxin. Only 49 % seeds of Arachis hypogaea germinated in presence of 1mM aflatoxin in the germinating medium compared to 71 % germination in control media.     

Influence of phylloplane colonizing biocontrol agents on the black spot of rose caused by Diplocarpon rosae

Abstract

An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplane of rose cv. Edward to manage the black spot (Diplocarpon rosae) disease. Eight antagonistic microorganisms were tested in vivo against the black spot pathogen. Among these, Trichoderma viride and Pseudomonas fluorescens pf1 reduces the mycelial growth significantly. These two biocontrol agents were evaluated for their ability to induce defense-related enzymes and chemicals in plants. Increased activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO) and total phenolics were recorded in all the biocontrol agents treated leaves. P. fluorescens Pf1 recorded early and increased synthesis of the entire defense-related enzymes and total phenol within 6 days. The application of biocontrol agents induced the defense-related enzymes involved in phenyl propanoid pathway in addition to direct antagonism, which collectively contribute for enhanced resistance against invasion of Diplocarpon rosae in rose.     

Effects of growth retardants on bulbil production by Narcissus twin-scales

Narcissus twin-scale propagules, cut from various positions in the parent bulb, were incubated with gibberellic acid (GA₃) or growth retardants. Bulbil production was inhibited in all cases by GA₃ at 10–100 mg/litre. Chlormequat chloride, chlorphonium chloride and paclobutrazol also inhibited bulbil production; in the case of paclobutrazol, outer twin-scales were more sensitive to lower concentrations of the retardant than inner ones. Ancymidol enhanced bulbil production (in numbers by up to 15%) in the outermost twin-scales, and had no stimulatory effect on the inner twin-scales. Treatments affected bulbil numbers and bulbil lengths about equally.