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.     

Exogenous Sodium Nitroprusside Mitigates Salt Stress in Lentil (Lens culinaris Medik.) by Affecting the Growth,Yield, and Biochemical Properties

Soil salinity disrupts the physiological and biochemical processes of crop plants and ultimately leads to compromising future food security. Sodium nitroprusside (SNP), a contributor to nitric oxide (NO), holds the potential to alleviate abiotic stress effects and boost tolerance in plants, whereas less information is available on its role in salt-stressed lentils. We examined the effect of exogenously applied SNP on salt-stressed lentil plants by monitoring plant growth and yield-related attributes, biochemistry of enzymes (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) amassing of leaf malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). Salinity stress was induced by NaCl application at concentrations of 50 mM (moderate salinity) and 100 mM (severe salinity), while it was alleviated by SNP application at concentrations of 50 µM and 100 µM. Salinity stress severely inhibited the length of roots and shoots, the relative water content, and the chlorophyll content of the leaves, the number of branches, pods, seeds, seed yield, and biomass per plant. In addition, MDA, H₂O₂ as well as SOD, CAT, and POD activities were increased with increasing salinity levels. Plants supplemented with SNP (100 µM) showed a significant improvement in the growth- and yield-contributing parameters, especially in plants grown under moderate salinity (50 mM NaCl). Essentially, the application of 100 µM SNP remained effective to rescue lentil plants under moderate salinity by regulating plant growth and biochemical pathways. Thus, the exogenous application of SNP could be developed as a useful strategy for improving the performance of lentil plants in salinity-prone environments.     

Flavonoids and strigolactones in root exudates as signals in symbiotic and pathogenic plant-fungus interactions

Secondary plant compounds are important signals in several symbiotic and pathogenic plant-microbe interactions. The present review is limited to two groups of secondary plant compounds, flavonoids and strigolactones, which have been reported in root exudates. Data on flavonoids as signaling compounds are available from several symbiotic and pathogenic plant-microbe interactions, whereas only recently initial data on the role of strigolactones as plant signals in the arbuscular mycorrhizal symbiosis have been reported. Data from other plant-microbe interactions and strigolactones are not available yet. In the present article we are focusing on flavonoids in plant-fungal interactions such as the arbuscular mycorrhizal (AM) association and the signaling between different Fusarium species and plants. Moreover the role of strigolactones in the AM association is discussed and new data on the effect of strigolactones on fungi, apart from arbuscular mycorrhizal fungi (AMF), are provided.     

Ascorbic Acid and Salicylic Acid Mitigate NaCl Stress in Caralluma tuberculata Calli

Plants exposed to salt stress undergo biochemical and morphological changes even at cellular level. Such changes also include activation of antioxidant enzymes to scavenge reactive oxygen species, while morphological changes are determined as deformation of membranes and organelles. Present investigation substantiates this phenomenon for Caralluma tuberculata calli when exposed to NaCl stress at different concentrations. Elevated levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in NaCl-stressed calli dwindled upon application of non-enzymatic antioxidants; ascorbic acid (AA) and salicylic acid (SA). Many fold increased enzymes concentrations trimmed down even below as present in the control calli. Electron microscopic images accentuated several cellular changes upon NaCl stress such as plasmolysed plasma membrane, disruption of nuclear membrane, increased numbers of nucleoli, alteration in shape and lamellar membrane system in plastid, and increased number of plastoglobuli. The cells retrieved their normal structure upon exposure to non-enzymatic antioxidants. The results of the present experiments conclude that NaCl aggravate oxidative molecules that eventually alleviate antioxidant enzymatic system. Furthermore, the salt stress knocked down by applying ascorbic acid and salicylic acid manifested by normal enzyme level and restoration of cellular structure.     

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.     

酸雨胁迫下小麦微弱延迟发光及其生理、生态变化相关性研究

以小麦幼苗为对象，研究了在酸雨胁迫下小麦叶片延迟发光强度变化与小麦叶 片内生理物质，包括叶绿素a，叶绿素b，类胡萝卜素，丙二醛，CAT，POD，SOD含 量变化及小麦生态变化的相关性．实验结果说明，在酸雨胁迫下延迟发光强度与小 麦抗逆过程中CAT，POD，SOD，类胡萝卜素和丙二醛含量变化，具有明显的一致性 ．CAT，POD，SOD指示着小麦组织内活性氧自由基和过氧化氢含量的变化，类胡萝 卜素和丙二醛也反映出小麦组织内氧化性物质含量的变化．说明延迟发光强度与植 物体内活性氧含量及还原性物质含量具有明确的相关性．由于上述各种生理变化与 植物抗病、抗逆机制密切相关，因此可以利用延迟发光结合生态变化作为综合性反 映植物抗逆过程的指标．     

Protective role of exogenous nitric oxide against oxidative-stress induced by salt stress in barley (Hordeum vulgare)

To probe into the potential of relieving the oxidative damage of salt stress, we investigated the protective role of nitric oxide on barley under salt stress. Salt stress resulted in increased ion leakage, lipid peroxidation and protein oxidation in barley leaves. Simultaneous treatments of barley leaves with 50 microM sodium nitroprusside, a nitric oxide donor, alleviated the damage of salt stress, reflected by decreased ion leakage, and malendialdehyde (MDA), carbonyl, and hydrogen peroxide content in barley leaves. The presence of the nitric oxide donor increased the activities of superoxide dismutases (SOD), ascorbate peroxidases (APX), and catalases (CAT). Meantime, sodium nitroprusside addition increased accumulation of ferritin at the protein level, indicating that nitric oxide directly regulated ferritin accumulation. These results suggested that nitric oxide can effectively protect seedlings from salt stress damage by enhancing activities of antioxidant enzymes to quench the excessive reactive oxygen species caused by salt stress and inducing the increase of ferritin accumulation to chelate larger number of ferrous ion. Information from this study can be used to improve soil management practices for sustainable use of salt-affected soils in the future.     

Effects of CO2 laser pretreatment on drought stress resistance in wheat

In order to determine the role of laser in drought stress resistance of spring wheat (Triticum aestivum L.), seed embryos were exposed to CO2 laser radiation for 0min, 1min, 3min and 5min, respectively, and when the seedlings were 12 days old they were treated with 10% (w/v) PEG6000 solution for 10 days. Changes in the concentration of malondialdehyde (MDA), hydrogen peroxide (H2O2), glutathione (GSH), ascorbate (AsA), oxidized glutathione (GSSG), carotenoid, zeaxanthin, the production rate of superoxide radical (O2(-)), the activities of ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GP), glutathione-S-transferase (GST) and the growth parameters of seedlings (plant height, leaf area and dry weight) were measured to test the effects of laser pretreatment. The results showed that suitable laser pretreatment of embryos enhanced drought stress resistance in wheat seedlings by decreasing the concentration of MDA and H2O2, GSSG, the production rate of O2(-), leaf area and increasing the activities of APX, GST, GP and POD and AsA, carotenoid and zeaxanthin concentration. It is suggested that those changes in MDA, O2(-) H2O2, anti-oxidative enzymes and anti-oxidative compounds were responsible for the increase in drought stress resistance observed in the experiments. The results also showed that the laser had a long-term positive physiological effect on the growth of drought stress seedlings. This is the first investigation reporting the use of CO2 laser pretreatment to enhance drought stress resistance of spring wheat.     

Antioxidant Response of Stevia rebaudiana B. to Polyethylene Glycol and Paclobutrazol Treatments Under In Vitro Culture

This investigation was carried out with the aim of determining the effect of paclobutrazol (PBZ) (0 and 2 mg l^?1) and polyethylene glycol (PEG) (0, 2, 4 and 6 %?w/v of PEG 6000) treatments on antioxidant system of Stevia rebaudiana Bertoni under in vitro condition. Analysis of data showed that PEG treatment significantly increased hydrogen peroxide (H₂O₂) and phenolic contents, while PBZ treatment limited the effect of PEG on them. Our data revealed that PEG treatment significantly increased total antioxidant capacity, catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and peroxidase (POD) activity, while it inversely decreased glutathione reductase (GR) activity. The superoxide dismutase (SOD) activity was not affected by PEG treatment. PBZ treatment induced significantly higher levels of CAT and GR activity and lower levels of SOD activity in PEG-treated plants. PBZ in combination with PEG resulted in no significant difference on APX activity with PEG treatment alone. PBZ treatment prevented the effect of PEG on the PPO activity. PEG (with or without PBZ) treatment increased the ascorbate pool, whereas total glutathione level was not affected by PEG. Our finding indicated that PBZ reduced the negative effect of PEG treatment by quenching H₂O₂ accumulation and increasing the CAT activity. Collectively, the antioxidant capacity of S. rebaudiana in PEG treatment condition was associated with active enzymatic and non-enzymatic defence systems which partly could be improved by the PBZ treatment. In addition, a higher accumulation of phenolic compounds leads to a more potent reactive oxygen species scavenging activity in S. rebaudiana.     

Health-Promoting Compounds in Stevia: The Effect of Mycorrhizal Symbiosis,Phosphorus Supply and Harvest Time

This work aimed to establish the synergic role of arbuscular mycorrhizal fungi (AMF) symbiosis, phosphorus (P) fertilization and harvest time on the contents of stevia secondary metabolites. Consequently, steviol glycosides (SVglys) concentration and profile, total phenols and flavonoids as well as antioxidant assays, have been assessed in inoculated and no-inoculated plants, grown with or without P supply and collected at different growth stages(69, 89 and 123 days after transplanting).The obtained results suggest that the synthesis of stevia secondary metabolites is induced and/or modulated by all the investigated variability factors. In particular, AMF symbiosis promoted total SVglys content and positively influenced the concentration of some minor compounds (steviolbioside, dulcoside A and rebaudioside B), indicating a clear effect of mycorrhizal inoculation on SVglys biosynthetic pathway. Interestingly, only the mycorrhizal plants were able to synthesize rebaudioside B. In addition, P supply provided the highest levels of total phenols and flavonoids at leaf level, together with the maximum in vitro antioxidant activities (FRAP and ORAC). Finally, the harvest time carried out during the full vegetative phase enhanced the entire composition of the phytocomplex (steviolbioside, dulcoside A, stevioside, rebaudioside A, B, C. total phenols and flavonoids). Moreover, polyphenols and SVglys appeared to be the main contributors to the in vitro antioxidant capacity, while only total phenols mostly contributed to the cellular antioxidant activity (CAA). These findings provide original information about the role played by AMF in association with P supply, in modulating the accumulation of bioactive compounds during stevia growth. At the cultivation level, the control of these preharvest factors, together with the most appropriate harvest time, can be used as tools for improving the nutraceutical value of raw material, with particular attention to its exploitation as functional ingredient for food and dietary supplements and cosmetics.