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Indian ginseng ( Withania somnifera L. Dunal), a medicinally important plant exposed to different concentrations of CuSO 4 (0, 10, 25, 50, 100 and 200 μM) for 30 d in vitro accumulated high amount of Cu in a concentration manner. Toxic effects of Cu on plants were reflected by the reductions in fresh weight (FW), shoot and root length, chlorophyll and carotenoids contents. Malondialdehyde (MDA), a decomposition product of polyunsaturated fatty acids hydroperoxides, often considered as a suitable biomarker for lipid peroxidation was induced in metal-treated plants compared to the control. This hypothesis is also confirmed by the higher lipoxygenase (LOX) activity, coupled with higher hydrogen peroxide (H 2 O 2 ) and superoxide anions (O 2 − ) content in treated plants. Ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione- S -transferase (GST) and guaiacol-peroxidase (G-POD) activities of leaves were increased in the presence of Cu when compared to control plants indicated that antioxidant enzymes played an important role in protecting the plant from Cu toxicity. After native polyacrylamide gel electrophoresis (PAGE) analysis, six APX and four G-POD isoforms were detected and significantly induced in metal-treated plants as compared to control plants. The marked decrease in superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPx) activities seems to reflect its inability for eliminating the reactive oxygen species (ROS) resulting from Cu-induced oxidative stress. On the other hand, total phenolic contents increased with increasing concentration of Cu compared to the control. This study reveals that plants have the ability to grow in Cu polluted areas by altering various physiological changes. Since the level of total phenolic content in metal-treated plants increases, therefore, it is advisable to assess the biological activity of the plants before using for medicinal purposes.

The aim of this study was to investigate the effect of CO2 at various concentrations (1, 2.5 and 5%) on antioxidant enzymes and ginsenoside accumulation in Panax ginseng roots in 5 l airlift bioreactors (working volume 4 l). One and 2.5% CO2 was beneficial for root biomass accumulation, but 5% CO2 decreased the biomass. Ginsenoside concentration decreased with increasing concentration of CO2. No significant difference was observed in the malondialdehyde (MDA) content and lipoxygenase (LOX) activity between respective controls and CO2 treated roots. Antioxidant enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR), catalase (CAT), guaiacol peroxidase (G-POD) including reduced ascorbate and total glutathione were induced in CO2 exposed roots which emphasized the protective role of antioxidants against CO2 induced stress. Superoxide dismutase activity (SOD) which was induced after 15 days was significantly inhibited after 45 days. Glutathione-S-transferase (GST) and glutathione peroxidase (GPX) activities also increased when the roots were subjected to 1 and 2.5% CO2 compared to the respective controls but not at 5%. A higher reduced ascorbate to oxidized (ASC/DHA) ratio in CO2 treated root indicates the plant's ability to tolerate CO2 stress. These observations suggest that an increase in antioxidant enzymes may affect a defense response to the cellular damage induced by CO2. Probably, this increase could not stop the deleterious effects of CO2 concentration on ginsenoside concentration, but reduced stress severity and thereby allowing root growth to occur.

Compared to non-embryogenic callus, proembryonic mass, globular, and heart-shaped embryos of Eleutherococcus senticosus had higher levels of endogenous reduced glutathione (GSH). GSH content declined during the course of the embryo development (torpedo and cotyledon). Similarly, glutathione reductase that is involved in the recycling of GSH providing a constant intracellular level of GSH was also higher in globular and heart-shaped embryos. The transient increase in GSH contents also correlated with the changes in measured γ-glutamylcysteine synthetase activity over the same period. The endogenous levels of oxidized glutathione showed similar trend during development of the somatic embryos, whereas it declined in maturing somatic embryos. A pronounced increase in glutathione-S-transferase, glutathione peroxidase, catalase, and guaiacol peroxidase activity was observed during somatic embryo maturation. Ascorbate-glutathione cycle enzymes (ascorbate peroxidase; dehydroascorbate reductase and monodehydroascorbate reductase) activities also induced indicated that antioxidant enzymes played an important role during embryo development. These results suggested that the coordinated up-regulations of the antioxidant enzymes and glutathione redox system provide protection during somatic embryo development in E. senticosus. Antioxidant responses through alterations of the glutathione redox systems, have been described in the present studies have a significant role in somatic embryo development.

A large number of micropropagated Euphorbia millii shoots from temporary immersion bioreactor showed thick broad leaves that were translucent, wrinkled and/or curled and brittle, symptoms of hyperhydricity. The environment inside bioreactor normally used in plant micropropagation is characterised by high relative humidity, poor gaseous exchange between the internal atmosphere of the bioreactor and its surrounding environment, and the accumulation of ethylene, conditions that may induce physiological disorders. A comparison of hyperhydric shoots (HS) with normal plants shows marked increase in malondialdehyde (MDA) content in HS plants. MDA, a decomposition product of polyunsaturated fatty acids hydroperoxides, has been utilized very often as a suitable biomarker for lipid peroxidation, which is an effect of oxidative damage. This hypothesis is also confirmed by the higher lipoxygenase (LOX) activity in HS plants. The potential role of antioxidant enzymes in protecting hyperhydric shoots from oxidative injury was examined by analyzing enzyme activities and isozyme profiles of hyperhydric and non-hyperhydric leaves of E. millii. Superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity were significantly higher in hyperhydric tissue as compared to non-hyperhydric normal leaf tissue. After native polyacrylamide gel electrophoresis (PAGE) analysis, seven SOD isoenzymes were detected and the increase in SOD activity observed in hyperhydric tissue seemed to be mainly due to Mn-SOD and Cu/Zn-SOD. The activity of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) was proportionally increased in HS tissue compared to normal leaves indicating a crucial role in eliminating toxic H2O2 from plant cells. The depletion of GSH and total glutathione in spite of higher GR activities observed in HS tissue indicates that mechanism of antioxidant defense was by enhanced oxidation of GSH to GSSG by DHAR yielding ascorbate (AA). The antioxidant metabolism has been shown to be important in determining the ability of plants to survive in hyperhydric stress and the up regulation of these enzymes would help to reduce the build up of ROS.

The effects of CO 2 levels (0.03, 0.5, 1, 2 and 5%) on growth and antioxidant responses in 5 l bioreactor (working volume 4 l) root suspension cultures of Echinacea angustifolia were studied. CO 2 caused reduction in growth, malondialdehyde content (MDA), lipoxygenase (LOX, EC 1.13.11.13) activity and superoxide anion (O 2 − ) accumulation along with high total phenols accumulation and pH levels. Maximal increases (37%) in total phenols were obtained at 1% CO 2 compared to the control. An increase in total glutathione and total ascorbate (ASC + DHA), accompanied with enhanced ascorbate–glutathione cycle enzymes were observed in CO 2 -treated roots, which played an important role for the detoxification of harmful substances. CO 2 also induced an increase in glutathione peroxidase (GPx, EC 1.11.1.9) and glutathione- S -transferase (GST, EC 2.5.18) activities. After native polyacrylamide gel electrophoresis (PAGE) analysis, three superoxide dismutase (SOD, EC 1.15.1.1) isoenzymes were detected. Increase in SOD and CAT (EC 1.11.16) activities observed at 0.5% CO 2 -treated roots and induced SOD activity seemed to be mainly due to Mn-SOD. However, both SOD and CAT activities were inhibited at 2 and 5% CO 2 but reached similar to control value. Three APX (EC 1.11.1.11) and three guaiacol peroxidase (G-POD, EC 1.11.1.7) isoenzymes were strongly detected, an increase in APX and G-POD activities suggests increased scavenging of ROS, indicating the tolerance to CO 2 . These results indicated that limited oxidative damage as shown by lower MDA level, low LOX activity and low O 2 − accumulation may be due to the induced activities of antioxidant enzymes and non-enzymatic antioxidant. It is therefore, suggested that roots cultured in a bioreactor could protect themselves from CO 2 by altering the defense systems.

In this study of tissue cultured Panax ginseng roots in bioreactor, growth responses, carbonyl content, phenolics, flavonoids, diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, cysteine, non-protein thiol (NPSH) content, phenolics related enzymes and lignin content were analysed after exposure to copper (Cu 2+ ) sulfate at various concentrations. Cu 2+ significantly inhibited root growth and resulted in an increase in protein oxidation (21%) (measured as carbonyl content) at 50 μM. Cu 2+ stress resulted in increased activities of glucose 6 phosphate dehydrogenase (G6PDH), shikimate dehydrogenase (SKDH), phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). The ensuing effect was an accumulation of phenolics and lignin. The phenolics, flavonoids, cysteine and NPSH contents as well as the DPPH activity, increased by 26%, 83%, 30%, 40% and 76%, respectively, at 50 μM Cu 2+ treatment compared to the control after 40 days. The induced activities of substrate specific peroxidases (caffeic acid peroxidase, CA-POD), chlorogenic acid peroxidase (CH-POD), polyphenol oxidase (PPO) and β-glucosidase (β-GS) indicated that these enzymes played an important role in the synthesis of phenolics compounds. The results also provided evidence that the application of Cu 2+ at 25 and 50 μM was accompanied by a substantial increase in oxidative stress as indicated by protein oxidation and reduced root growth. The increase in phenolic compounds, related enzymes and lignin clearly reflects the protective response to cellular damage induced by higher levels of Cu 2+ .

Somatic embryos of Eleutherococcus senticosus were exposed at 12, 16, 24 and 30 °C for duration of 45 days in bioreactor. The effects of such treatments on the growth, eleutheroside B, E, E1, total phenolics, flavonoids, chlorogenic acid concentrations and antioxidant enzymes activities were investigated. The results revealed that low (12 and 18 °C) and high (30 °C) temperature caused significant decrease in fresh weight (FW), dry weight (DW), total phenolics, flavonoids and total eleutheroside accumulation, while low temperature increased eleutheroside E accumulation in somatic embryos. Low temperature significantly increased superoxide dismutase (SOD), catalase (CAT), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) activities whereas a strong increase in ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activity was obtained at 12 °C grown somatic embryos. In contrast, high temperature significantly decreased antioxidant enzymes activities and even guaiacol peroxidase (G-POD) activity also decreased at low temperature in comparison to 24 °C grown embryos. These data suggest that low and high temperature treatment provoked an oxidative stress in E. senticosus embryos, as shown by the increase in lipid peroxidation. The increase in lipid peroxidation was paralleled by a rise in lipoxygenase (LOX) activity and hydrogen peroxide (H2O2) content. However, this stress was more prominent at high temperature than low temperature grown embryos. This result suggests that the reduced growth of embryo at 30 °C was concomitant with reduced efficiency of these protective enzymes. On the other hand, increases in antioxidant activities at 12 and 18 °C could also be a response to the cellular damage; however, this increase could not stop the deleterious effects of low temperature, but reduced stress severity thus allowing embryo growth to occur.

The effect of initial sucrose concentration was investigated in embryogenic cell cultures of Eleutherococcus sessiliflorus in bioreactors for production of eleutherosides, phenol, flavonoids and polysaccharide. The final dry cell weight was increased from 6.16 to 23.33 g l −1 with an increase of initial sucrose concentration from 10 to 70 g l −1 , but an even higher sucrose concentration of 90 g l −1 seemed to repress the cell growth. Furthermore, it was found that a high sugar level was favorable to the synthesis of eleutherosides, phenol and flavonoids, which may be due to higher osmotic pressure. A marked increase in malondialdehyde (MDA) content in germinating embryos was observed in high sucrose treatment. MDA, a decomposition product of polyunsaturated fatty acids hydroperoxides, has been utilized very often as a suitable biomarker for lipid peroxidation, which is an effect of osmotic stress. This hypothesis is also confirmed by the higher lipoxygenase (LOX) activity under this treatment. The much higher antioxidant enzyme activities in the culture fed with higher initial sucrose suggest that osmotic stress arising from a sudden increase in medium osmotic pressure. A hypothesis of osmotic stress and eleutheroside accumulation was confirmed from these results.

Roots of mountain ginseng (Panax ginseng) were exposed to various levels of oxygen (O2) (30, 40 and 50%) for 15, 30 and 45 days in 5 L (working volume 4 L) airlift bioreactors. Ginsenoside accumulation and dry weight was enhanced up to 40% O2; but thereafter declined ginsenoside and dry weight of the roots by increasing level of O2. Gradual increase in H2O2 content and lipoxygenase activity (LOX), resulting in cellular damage and oxidative stress as indicated by increased malondialdehyde (MDA) content after 30 and 45 days at all O2 levels was shown. Increased levels of O2 (above ambient) resulted in increases in non-protein thiol (NP-SH) and cysteine content. Higher activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), catalase (CAT), guaiacol peroxidase (G-POD), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S transferase (GST) activities indicated that antioxidant enzymes played an important role in protecting the roots from O2 up to 45 days, except at 50% O2 where GR, GST and GPx decreased compared to the control. However, after 45 days, SOD activity decreased significantly compared to the control in the O2-treated roots. This reflects the sensitivity of enzymes to O2 toxicity. In stress related experiment, roots showed increased synthesis of ginsenosides when 25 and 50 μM H2O2 was applied. However, higher dose and increasing treatment inhibited ginsenoside synthesis. The results indicate that plant roots could grow and protect themselves from O2 stress by coordinated induction of various antioxidant enzymes and metabolite contents. These results suggest that O2 supplementation is useful for ginsenoside accumulation using 5-L bioreactors.

The oxidative status (anti-oxidative enzymes and anti-oxidants), saponins accumulation H 2 O 2 content and thiobarbituric acid reacting substances (TBARS) of tissue cultured roots of Panax ginseng (PG) and Panax quinquefolium (PQ) exposed to methyl jasmonate (MJ-200 μM) for 0, 3, 5, 7 and 9 days were studied in 5 L (working volume-4 L) airlift bioreactors. Saponin accumulation was enhanced 4-fold higher than the cultivated ginseng by elicitation with MJ without changing dry weight (DW). Decrease in TBARS and dehydroascorbate (DHA) contents along with the induced activity of superoxide dismutase (SOD), guaiacol peroxidase (G-POD) and reduced ascorbate (ASC) contents indicated that anti-oxidant played an important role for protecting plant from MJ elicitation. Seven well-resolved bands of SOD were detected after native polyacrylamide gel electrophoresis (PAGE) analysis, and increase in SOD activity observed in MJ-treated roots seemed to be mainly due to Fe-SOD. One G-POD and two catalase (CAT) isoenzymes (CAT 1 and 2) were also detected in both species significantly. MJ strongly induced G-POD activity and isoenzyme in PG than PQ while CAT activity and isozymes patterns inhibited in both species. Ascorbate peroxidase (APX) in PG and dehydroascorbate reductase (DHAR) in PQ was activated indicating a mechanism of protection from MJ elicitation. In addition, MJ resulted in the decrease of monodehydroascorbate reductase (MDHAR), glutathione reductase (GR), glutathione- S -transferase (GST) and glutathione peroxidase (GPX) activities in both species, which impaired detoxification process. However, GR activity was induced after 9 days of the MJ treatments in PQ. Ascorbate oxidase (AO) activity, ASC contents and ASC/DHA ratio increased after MJ treatment in both species, but DHA content decreased in PQ and remain unchanged in PG compared to control. These data suggest that MJ treatment showed limited oxidative stress in both species, as shown by the decrease in TBARS, in spite of the induction of lipoxygenase (LOX) activity and H 2 O 2 content, which was further correlated with the induced activities of SOD, G-POD, AO and ASC content. Therefore, MJ elicitation is useful for saponin production using 4 L bioreactor root suspension culture.

Higher plants growing in natural environments experience various abiotic stresses. The aim of this study was to determine whether exposure to temperature-stress would lead to oxidative stress and whether this effect varied with different exposure periods. The thermal dependencies of the activities of protective enzymes, photosynthetic efficiency (Fv/Fm), protein, non-protein thiol (NP-SH), cysteine content, lipoxygenase (LOX) activity (EC 1.13.11.12) and malondialdehyde (MDA) content at 25-40 degrees C were determined for 4, 24 and 48 h in leaf and root segments of Phalaenopsis. The increase in MDA level and LOX activity may be due to temperature-associated oxidative damage to leaf and root segments. Temperature-stress induced not only activities of active oxygen species (AOS) scavenging enzymes but also protein, NP-SH and cysteine content in both leaf and root segments at 30 degrees C for 4 and 24 h (except for 48 h in some cases) compared to 25 degrees C-and greenhouse-grown leaf and root segments indicating that antioxidants enzymes played an important role in protecting plant from temperature-stress. However, activities of dehydroascorbate reductase (DHAR, EC 1.8.5.1), glutathione peroxidase (GPX, EC 1.11.1.9) and glutathione-S-transferase (GST, EC 2.5.1.18) in leaf and root, glutathione reductase (GR, EC 1.6.4.2) in leaf and guaiacol peroxidase (G-POD, 1.11.1.7) in root segments were induced significantly at 40 degrees C compared to 25 degrees C and greenhouse-grown plants suggesting that these enzymes play protective roles at high temperature. In contrast, activities of superoxide dismutase (SOD, EC 1.15.1.1) and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) in leaf and root, catalase (CAT, EC 1.11.1.6) in root, GR in root, and protein, cysteine, NP-SH content in both root and leaf and Fv/Fm ratio were diminished significantly at 40 degrees C compared to 25 degrees C-and greenhouse-grown plants. These indicate that these enzymes were apparently not involved in detoxification process and sensitive at higher temperature. Also, the close relation between activities of enzymes with their metabolites at 30 degrees C than 40 degrees C indicated that the antioxidants enzymes and metabolites both may play an important role in protecting cells against the temperature-stress.

We studied how the relationship between cadmium (Cd) toxicity and oxidative stress influenced the growth, photosynthetic efficiency, lipid peroxidation, and activity of ntioxidative enzymes in the roots and leaves of rice(Oryza sativa L Dongjin). Plants were exposed to Cd for 21 d. Both seedling growth and photosynthetic efficiency decreased gradually with increasing cadmium concentrations. Lipid peroxidation increased slowly in both roots and leaves, causing oxidative stress. However, each tissue type responded differently to Cd concentrations with regard to the induction/ inhibition of antioxidative enzymes. The activity of Superoxide dismutase (SOD) increased in both roots and leaves. Ascorbate peroxidase (APX) activity increased in leaves treated with up to 0.25 µM Cd, then decreased gradually at higher concentrations. In contrast, APX activity in roots increased and remained constant between 0.25 and 25 µM Cd. Enhanced peroxidase (POD) activity was recorded for treatments with up to 25/M Cd, gradually decreasing at higher concentrations in the leaves but remaining unchanged in the roots. Catalase (CAT) activity increased in the roots, but decreased in the leaves, whereas the activity of glutathione reductase (GR) was enhanced in both roots and leaves, where it remained elevated at higher Cd concentrations. These results suggest that rice seedlings tend to cope with free radicals generated by Cd through coordinated, enhanced activities of the antioxidative enzymes involved in detoxification.

We studied the effects of different concentrations of mercury (0.0 to 100 µM) on growth and photosynthetic efficiency in rice plants treated for 21 d. In addition, we investigated how this metal affected the malondialdehyde (MDA) content as well as the activity of five antioxidant enzymes — superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), guaiacol peroxidase (POD), and catalase (CAT). Photosynthetic efficiency (Fµ/Fm) and seedling growth decreased as the concentration of Hg was increased in the growth media. Plants also responded to Hg-induced oxidative stress by changing the levels of their antioxidative enzymes. Enhanced lipid peroxidation was observed in both leaves and roots that had been exposed to oxidative stress, with leaves showing higher enzymatic activity. Both SOD and APX activities increased in treatments with up to 50 µM Hg, then decreased at higher concentrations. In the leaves, both CAT and POD activities increased gradually, with CAT levels decreasing at higher concentrations. In the roots, however, CAT activity remained unchanged while that of POD increased a bit more than did the control for concentrations of up to 10 µM Hg. At higher Hg levels, both CAT and POD activities decreased. GR activity increased in leaves exposed to no more than 0.25 µM Hg, then decreased gradually. In contrast, its activity was greatly inhibited in the roots. Based on these results, we suggest that when rice plants are exposed to different concentrations of mercury, their antioxidative enzymes become involved in defense mechanisms against the free radicals that are induced by this stress.

To investigate the enzyme variations responsible for the synthesis of phenolics, 40 day-old adventitious roots of Panax ginseng were treated with 200 microM methyl jasmonate (MJ) or salicylic acid (SA) in a 5 L bioreactor suspension culture (working volume 4 L). Both treatments caused an increase in the carbonyl and hydrogen peroxide (H2O2) contents, although the levels were lower in SA treated roots. Total phenolic, flavonoid, ascorbic acid, non-protein thiol (NPSH) and cysteine contents and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical reducing activity were increased by MJ and SA. Fresh weight (FW) and dry weight (DW) decreased significantly after 9 days of exposure to SA and MJ. The highest total phenolics (62%), DPPH activity (40%), flavonoids (88%), ascorbic acid (55%), NPSH (33%), and cysteine (62%) contents compared to control were obtained after 9 days in SA treated roots. The activities of glucose 6-phosphate dehydrogenase, phenylalanine ammonia lyase, substrate specific peroxidases (caffeic acid peroxidase, quercetin peroxidase and ferulic acid peroxidase) were higher in MJ treated roots than the SA treated ones. Increased shikimate dehydrogenase, chlorogenic acid peroxidase and beta-glucosidase activities and proline content were observed in SA treated roots than in MJ ones. Cinnamyl alcohol dehydrogenase activity remained unaffected by both MJ and SA. These results strongly indicate that MJ and SA induce the accumulation of phenolic compounds in ginseng root by altering the phenolic synthesis enzymes.

Roots of Panax ginseng exposed to various concentrations of Cu (0.0, 5, 10.0, 25.0, and 50.0 microM) accumulated high amounts of Cu in a concentration-dependent and duration-dependent manner. Roots treated with 50 microM Cu resulted in 52% and 89% growth inhibition after 20 and 40 days, respectively. Saponin synthesis was stimulated at a Cu concentration between 5 and 25 muM but decreased at 50 microM Cu. Malondialdehyde content (MDA), lipoxygenase activity (LOX), superoxide ion (O2*-) accumulation, and H2O2 content at 5 and 10 microM Cu-treated roots were not increased but strongly increased at 50 microM Cu resulting in the oxidation of ascorbate (ASC) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively indicating a clear oxidative stress. Seven well-resolved bands of superoxide dismutase (SOD) were detected in the gel and an increase in SOD activity seemed to be mainly due to the induction of Fe-SOD 3. Five to 10 microM Cu slightly induced activity of ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR), guaiacol peroxidase (G-POD) but inhibited monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) enzyme activities. No changes in catalase (CAT) activity and in activity gel were found up to 25 microM Cu, but both G-POD and CAT activities were inhibited at 50 microM Cu. Glutathione metabolism enzymes such as gamma-glutamylcysteine synthetase (gamma-GCS), glutathione-S-transferase (GST), and glutathione peroxidase activities (GPx) were activated at 5 and 10 microM Cu but were strongly inhibited at 50 microM Cu due to the Cu accumulation in root tissues. The strong depletion of GSH at 50 microM Cu was associated to the strong induction of gamma-glutamyltranspeptidase (gamma-GGT) activity. These results indicate that plant could grow under Cu stress (5-25 microM) by modulating the antioxidant defense mechanism for combating Cu induced oxidative stress.

The effects of methyl jasmonate (MJ) and salicylic acid (SA) on changes of the activities of major antioxidant enzymes, superoxide anion accumulation (O2-), ascorbate, total glutathione (TG), malondialdehyde (MDA) content and ginsenoside accumulation were investigated in ginseng roots (Panax ginseng L.) in 4 l (working volume) air lift bioreactors. Single treatment of 200 microM MJ and SA to P. ginseng roots enhanced ginsenoside accumulation compared to the control and harvested 3, 5, 7 and 9 days after treatment. MJ and SA treatment induced an oxidative stress in P. ginseng roots, as shown by an increase in lipid peroxidation due to rise in O2- accumulation. Activity of superoxide dismutase (SOD) was inhibited in MJ-treated roots, while the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), SOD, guaiacol peroxidase (G-POD), glutathione peroxidase (GPx) and glutathione reductase (GR) were induced in SA-treated roots. A strong decrease in the activity of catalase (CAT) was obtained in both MJ- and SA-treated roots. Activities of ascorbate peroxidase (APX) and glutathione S transferase (GST) were higher in MJ than SA while the contents of reduced ascorbate (ASC), redox state (ASC/(ASC+DHA)) and TG were higher in SA- than MJ-treated roots while oxidized ascorbate (DHA) decreased in both cases. The result of these analyses suggests that roots are better protected against the O2- stress, thus mitigating MJ and SA stress. The information obtained in this work is useful for efficient large-scale production of ginsenoside by plant-root cultures.

Background The production and use of biologically derived soil additives is one of the fastest growing sectors of the fertilizer industry. These products have been shown to improve crop yields while at the same time reducing fertilizer inputs to and nutrient loss from cropland. The mechanisms driving the changes in primary productivity and soil processes are poorly understood and little is known about changes in secondary productivity associated with the use of microbial products. Here we investigate secondary metabolic responses to a biologically derived soil additive by monitoring changes in the phenlypropanoid (PP) pathway in Arabidopsis thaliana. Results This study was designed to test the influence of one of these products (Soil Builder™-AF, SB) on secondary metabolism after being applied at different times. One time (TI) application of SB to Arabidopsis increased the accumulation of flavonoids compared to multiple (TII) applications of the same products. Fourteen phenolic compounds including flavonols and anothocyanins were identified by mass spectrometry. Kaempferol-3,7-O-bis-α-L-rhamnoside and quercetin 3,7-dirhamnoside, the major compounds, increased 3-fold and 4-fold, respectively compared to control in the TI treatment. The most abundant anthocyanin was cyanidin 3-rhamnoglucoside, which increased 3-fold and 2-fold in TI compared to the control and TII, respectively. Simultaneously, the expression of genes coding for key enzymes in the PP pathway (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, chalcone synthase, flavonoid-3′-O-hydroxylase, flavonol synthase1 and dihydroflavonol-4-reductase) and regulatory genes (production of anthocyanin pigment2, MYB12, MYB113, MYB114, EGL3, and TT8) were up-regulated in both treatments (TI and TII). Furthermore, application of TI and TII induced expression of the lignin pathway genes (hydroxyl cinamyl transferase, caffeyl-CoA O-methyl transferase, cinnamyl alcohol dehydrogenase, cinnamyl-CoA reductase, secondary wall-associated NAC domain protein1, MYB58 and MYB63 resulting in higher accumulation of lignin content compared to the control. Conclusions These results indicate that the additions of microbially based soil additives have a perceptible influence on phenylpropanoid pathway gene regulation and its production of secondary metabolites. These findings open an avenue of research to investigate the mode of action of microbially-based soil additives which may assist in the sustainable production of food, feed, fuel and fiber.