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Xiaohui Hu – One of the best experts on this subject based on the ideXlab platform.

  • exogenous spermidine is enhancing tomato tolerance to salinity Alkalinity stress by regulating chloroplast antioxidant system and chlorophyll metabolism
    BMC Plant Biology, 2015
    Co-Authors: Jianming Li, Lipan Hu, Li Zhang, Xiaohui Hu


    Salinity–Alkalinity stress is known to adversely affect a variety of processes in plants, thus inhibiting growth and decreasing crop yield. Polyamines protect plants against a variety of environmental stresses. However, whether exogenous spermidine increases the tolerance of tomato seedlings via effects on chloroplast antioxidant enzymes and chlorophyll metabolism is unknown. In this study, we examined the effect of exogenous spermidine on chlorophyll synthesis and degradation pathway intermediates and related enzyme activities, as well as chloroplast ultrastructure, gene expression, and antioxidants in salinity–Alkalinity–stressed tomato seedlings. Salinity–Alkalinity stress disrupted chlorophyll metabolism and hindered uroorphyrinogen III conversion to protoporphyrin IX. These effects were more pronounced in seedlings of cultivar Zhongza No. 9 than cultivar Jinpengchaoguan. Under salinity–Alkalinity stress, exogenous spermidine alleviated decreases in the contents of total chlorophyll and chlorophyll a and b in seedlings of both cultivars following 4 days of stress. With extended stress, exogenous spermidine reduced the accumulation of δ–aminolevulinic acid, porphobilinogen, and uroorphyrinogen III and increased the levels of protoporphyrin IX, Mg–protoporphyrin IX, and protochlorophyllide, suggesting that spermidine promotes the conversion of uroorphyrinogen III to protoporphyrin IX. The effect occurred earlier in cultivar Jinpengchaoguan than in cultivar Zhongza No. 9. Exogenous spermidine also alleviated the stress–induced increases in malondialdehyde content, superoxide radical generation rate, chlorophyllase activity, and expression of the chlorophyllase gene and the stress–induced decreases in the activities of antioxidant enzymes, antioxidants, and expression of the porphobilinogen deaminase gene. In addition, exogenous spermidine stabilized the chloroplast ultrastructure in stressed tomato seedlings. The tomato cultivars examined exhibited different capacities for responding to salinity–Alkalinity stress. Exogenous spermidine triggers effective protection against damage induced by salinity–Alkalinity stress in tomato seedlings, probably by maintaining chloroplast structural integrity and alleviating salinity–Alkalinity–induced oxidative damage, most likely through regulation of chlorophyll metabolism and the enzymatic and non–enzymatic antioxidant systems in chloroplast. Exogenous spermidine also exerts positive effects at the transcription level, such as down–regulation of the expression of the chlorophyllase gene and up–regulation of the expression of the porphobilinogen deaminase gene.

  • effect of exogenous spermidine on polyamine content and metabolism in tomato exposed to salinity Alkalinity mixed stress
    Plant Physiology and Biochemistry, 2012
    Co-Authors: Xiaohui Hu, Yi Zhang, Zhi Zhang, Hao Zhang, Jiuzhou Zhao


    Abstract We investigated the effects of seeds pretreatment with exogenous spermidine (Spd) on the polyamine content and metabolism in the roots of two cultivars of tomato (Solanum lycopersicum), Jinpengchaoguan and Zhongza No. 9 grown under conditions of mixed salinity–Alkalinity stress. These cultivars differ in their tolerance to salinity stress, with the former more tolerant than the latter. PA content, whether in its free forms, soluble conjugated forms, or insoluble bound forms, increased significantly during salinity–Alkalinity stress. The activities of S-adenosylmethionine decarboxylase (SAMDC) and diamine oxidase (DAO), concentrations of free Spd, soluble conjugated forms of Spd and spermine (Spm), and insoluble bound form of Spd in the roots were enhanced to a greater extent in cv. Jinpengchaoguan roots than in cv. Zhongza No.9 in response to salinity–Alkalinity stress. Interestingly, Spd application to seeds markedly suppressed the accumulation of free Put, but promoted an increase in free Spd and Spm concentrations, as well as soluble conjugated forms of Spd and insoluble bound forms of Put in both cultivars. From these data, we deduced that exogenous Spd promotes the conversion of free Put into free Spd and Spm, and soluble conjugated forms and insoluble bound forms of PAs under salinity–Alkalinity stress. Furthermore, under salinity–Alkalinity stress conditions, exogenous Spd enhanced the activities of ODC, SAMDC and DAO, and reduced the activities of ADC and polyamine oxidase (PAO) in cv. Zhongza No.9 roots. In addition, exogenous Spd reduced the activities of ADC and ODC, and increased the activities of DAO and SAMDC in cv. Jinpengchaoguan roots under salinity–Alkalinity stress conditions. These results suggest that exogenous Spd treatment can regulate the metabolic status of polyamines caused by salinity–Alkalinity stress, and eventually enhance tolerance of tomato plants to salinity–Alkalinity stress. Additionally, Spd treatments have varying effects on different tolerant tomato cultivars.

Alberto Zirino – One of the best experts on this subject based on the ideXlab platform.

  • ph Alkalinity and total co2 in coastal seawater by potentiometric titration with a difference derivative readout
    Analytica Chimica Acta, 1999
    Co-Authors: Martin J Hernandezayon, Alberto Zirino, Stuart L Belli


    Abstract A method for measuring three components of the CO2 system, pH, Alkalinity (At) and total CO2 (TCO2) in coastal seawater is presented. The measurements are sufficiently precise to register CO2 changes of biological origin in surficial and coastal waters or in culture media. The method is based on a modified potentiometric titration of seawater with acid in a custom-built cell with the data plotted as a difference derivative, giving two peaks from which total carbonate and Alkalinity can be computed. pH is calculated directly from the initial millivolt reading of the sample. One important aspect of this technique is that, unlike a Gran titration, the measured values of pH, At and TCO2 are independent of any pre-conceived seawater model. In this work we demonstrate that the relative position of the two peaks (used for determining TCO2) is relatively insensitive to interferences from dissolved organic matter to about 1 × 10−4 M, while peak height is sensitive to it. This last observation permits the detection of organic bases which might be included in the measurement of Alkalinity.

Delia Teresa Sponza – One of the best experts on this subject based on the ideXlab platform.

  • effect of Alkalinity on the performance of a simulated landfill bioreactor digesting organic solid wastes
    Chemosphere, 2005
    Co-Authors: Osman Nuri Agdag, Delia Teresa Sponza


    This study investigated the effects of Alkalinity on the anaerobic treatment of the organic solid wastes collected from the kitchen of Engineering Faculty in Dokuz Eylul University, Izmir, Turkey and the leachate characteristics treated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation. One reactor was operated without Alkalinity addition. The second reactor was operated by the addition of 3 g l-1 d-1 of NaHCO3 Alkalinity to the leachate and the third reactor was operated by the addition of 6 g l-1 d-1 NaHCO3 Alkalinity to the leachate. After 65 d of anaerobic incubation, it was observed that the chemical oxygen demand (COD), volatile fatty acids (VFA) concentrations, and biochemical oxygen demand to chemical oxygen demand (BOD5/COD) ratios in the leachate samples produced from the Alkalinity added reactors were lower than the control reactor while the pH values were higher than the control reactor. The COD values were measured as 18900, 3800 and 2900 mg l-1 while the VFA concentrations were 6900, 1400 and 1290 mg l-1, respectively, in the leachate samples of the control, and reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 after 65 d of anaerobic incubation. The total nitrogen (TN), total phosphorus (TP) and ammonium nitrogen (NH4-N) concentrations in organic solid waste (OSW) significantly reduced in the reactor containing 6 g l-1 NaHCO3 by d 65. The values of pH were 6.54, 7.19 and 7.31, after 65 d of anaerobic incubation, respectively, in the aforementioned reactors results in neutral environmental conditions in Alkalinity added reactors. Methane percentage of the control, reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 were 37%, 64% and 65%, respectively, after 65 d of incubation. BOD5/COD ratios of 0.27 and 0.25 were achieved in the 3 and 6 g l-1 NaHCO3 containing reactors, indicating a better OSW stabilization. Alkalinity addition reduced the waste quantity, the organic content of the solid waste and the biodegradation time.

  • effects of Alkalinity and co substrate on the performance of an upflow anaerobic sludge blanket uasb reactor through decolorization of congo red azo dye
    Bioresource Technology, 2005
    Co-Authors: Mustafa Isik, Delia Teresa Sponza


    Abstract The effect of substrate (glucose) concentrations and alkalinitiy (NaHCO 3 ) on the decolorization of a synthetic wastewater containing Congo Red (CR) azo dye was performed in an upflow anaerobic sludge blanket (UASB). Color removal efficiencies approaching 100% were obtained at glucose-COD concentrations varying between 0 and 3000 mg/l. The methane production rate and total aromatic amine (TAA) removal efficiencies were found to be 120 ml per day and 43%, respectively, while the color was completely removed during glucose-COD free operation of the UASB reactor. The complete decolorization of CR dye under co-substrate free operation could be attributed to TAA metabolism which may provide the electrons required for the cleavage of azo bond in CR dye exist in the UASB reactor. No significant differences in pH levels (6.6–7.4), methane production rates (2000–2700 ml/day) and COD removal efficiencies (82–90%) were obtained for NAHCO 3 concentrations ranging between 550 and 3000 mg/l. However, decolorization efficiency remained at 100% with decreasing NaHCO 3 concentrations as low as 250 mg/l in the feed. An Alkalinity/COD ratio of 0.163 in the feed was suggested for simultaneous optimum COD and color removal.