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The association between terrestrial plants and arbuscular mycorrhizal (AM) fungi is one of the most common and widespread mutualistic plant-fungi interaction. AM fungi are of beneficial effects on the water and nutrient uptake of plants and increase plant defense mechanisms to alleviate different stresses. The aim of this study was to determine the level of polyphenol oxidase (PPO), guaiacol peroxidase (POX) and glutathione S-transferase (GST) enzyme activities and to track the expression of glutathione S-transferase (GST) gene in plant-arbuscular mycorrhizal system under temperature- and mechanical stress conditions. Our results suggest that induced tolerance of mycorrhizal sunflower to high temperature may be attributed to the induction of GST, POX and PPO enzyme activities as well as to the elevated expression of GST. However, the degree of tolerance of the plant is significantly influenced by the age which is probably justified by the energy considerations.
Activities of superoxide dismutase (SOD), guaiacol peroxidase (PX), glutahione peroxidase (GPX) and catalase (CAT) as well as formation of malondialdehyde (MDA) and liposoluble fluorescent compounds (LFC) in leaves of 20 wheat genotypes, parents and hybrids of F1 and F2 generation were examined. The aim was to determine inheriting pattern of investigated parameters and relation between antioxidative enzyme activities and lipid peroxidation and LFC formation. No consistent role of inheritance of antioxidant parameters was found. Investigated genotypes and hybrids, among themselves, differed significantly in antioxidative enzyme activities and MDA and LFC content. Results presented indicate that high contents of MDA and LFC are associated with low activities of antioxidative enzymes. Also, relatively small quantities of MDA and LFC are associated with high activities of SOD and CAT.
Hydrogen sulfide (H2S) has been recently found to be a gaseous signaling molecule in plants. In this work, we studied the role of H2S in alleviating salinity stress during wheat grain germination (Triticum aestivum L. Yangmai 158). Pretreatment with NaHS, a H2S donor, during wheat grain imbibition, could significantly attenuate the inhibitory effect of salinity stress on wheat germination. NaHS-pretreated grain showed higher amylase and esterase activities than water control. NaHS pretreatment differentially stimulated the activities of catalase (CAT), guaiacol peroxidase (POD) and ascorbate peroxidase (APX), decreased the level of malondialdehyde (MDA) and reduced NaCl-induced changes in plasma membrane integrity in the radicle tips of seedlings compared with water control. We conclude that H2S plays an important role in protecting wheat grain from oxidative damage induced by salinity stress.
Volatile constituents of four red pepper (called paprika in Hungarian) cultivars of the famous Szeged paprika growing region were analysed by GC-MS measurements subsequent to Likens-Nickerson simultaneous distillation extraction (LN-SDE) sample preparation. Of the compounds, 107 common constituents were managed to be identified. The examination detected the presence of terpenes, esters, hydrocarbons, acids, alcohols, aldehydes, and ketones. Several sulphur, cyclic nitrogen, and oxygen containing compounds were found as well, which usually present fairly high odour activities. The most abundant components in the examined cultivars were the hexadecanoic acid, tetradecanoic acid, dodecanoic acid, 4-vinyl-2-methoxy-phenol (4-vinyl guaiacol), and a compound of unknown structure. Though many pyrazines and relative substances occurred in the samples, 2-methoxy-3-isobutylpyrazine, responsible for the fresh red bell pepper note, could not be detected.
Abstract
Thermogravimetry-mass spectrometry (TG-MS) was used to study the effect of the inorganic salts (NH4)2SO4 and (NH4)2HPO4, active substances of many commercial forest fire retardants, on the pyrolysis of Pinus halepensis needles and their main components (cellulose, lignin and extractives). These salts seemed to affect the pyrolysis of cellulose by increasing significantly the char residue, decreasing the pyrolysis temperature and changing the composition of the evolved gases, that is, increasing levoglucosenone and decreasing oxygen containing volatile products. (NH4)2SO4 seemed to have negligible effect on the pyrolysis of lignin, while (NH4)2HPO4 increased the char residue and decrease the relative contribution of guaiacols in the evolved gases. No effects of the inorganic salts on the extractives were observed. Finally, the inorganic salts seemed to affect the pyrolysis of pine-needles, mainly the cellulose component, but the effects were not as intense as in the pyrolysis of cellulose.
Stress tolerance is associated with the activation of antioxidant compounds and enzyme systems that are capable of neutralising the reactive oxygen species (ROS) continually produced in response to stress. The present experiment was designed to compare the heat tolerance of four winter wheat varieties in the shooting and grain-filling stages by investigating changes detected in antioxidant enzyme activity and yield components in response to heat stress.Heat treatment was found to cause a significant rise in the activity of the glutathione-S-transferase and catalase enzymes, while there was usually a less intense decline in the activity of guaiacol peroxidase.An analysis of yield data revealed that heat stress had a more pronounced effect during grain filling in this experiment than at the beginning of shooting, as shown by the greater reduction in thousand-kernel weight and yield.
On brief exposure of Azolla fronds to salinity stress, a significant decrease in photosynthetic pigment like chlorophyll and carotenoid with a decrease in ascorbate and glutathione content was observed. Lipid peroxidation increases with doses of NaCl stress resulting a greater membrane damage supported by increase in superoxide radical. However, increase in activities of superoxide dismutase, catalase, guaiacol peroxidase and glutathione reductase showed the development of biochemical defence mechanism against free radicals generated during exposure to short-term salinity stress. K+ ion was found to be decreased with increasing NaCl concentration, with a decrease in relative water content. An increase in fresh mass was observed, with a significant increase in dry mass suggested a development of salt tolerance in Azolla exposed to short-term salinity stress.
Abstract
The combined analytical methods of thermal analysis and mass spectrometry have been applied in form of a newly developed prototype of a thermogravimetry — single photon ionisation time-of-flight mass spectrometer coupling (TG-SPI-TOFMS) to investigate the molecular patterns of evolved gases from several biomass samples as well as a crude oil sample. Single photon ionization (SPI) was conducted by means of a novel electron beam pumped argon excimer lamp (EBEL) as photon source. With SPI-TOFMS various lignin decomposition products such as guaiacol, syringol and coniferyl alcohol could be monitored. Furthermore, SPI allows the detection of aliphatic hydrocarbons, mainly alkenes, carbonylic compounds such as acetone, and furan derivatives such as furfuryl alcohol and hydroxymethylfurfural. More alkaline biomass such as coarse colza meal show intense signals from nitrogen containing substances such as (iso-)propylamine and pyrrole. Thermal degradation of crude oil takes place in two steps, evaporation of volatile components and pyrolysis of larger molecular structures at higher temperatures. Due to the soft ionisation, homologue rows of alkanes and alkenes could be detected on basis of their molecular ions. The obtained information from the thermal analysis/photo ionisation mass spectrometry experiments can be drawn on in comparison to the investigation of the primary products from flash pyrolysis of biomass for production of biofuels and chemicals.
The effect of copper excess (CuSO 4 ) on lipid peroxidation, H 2 O 2 content, and antioxidative enzyme activities was studied in primary leaves of bean seedlings. Fourteen-day-old bean seedlings were cultured in a nutrient solution containing Cu 2+ at various concentrations (50 and 75 μM) for 3 days. Excess of copper significantly increased malondialdehyde content and endogenous H 2 O 2 . This radical accumulated in the intercellular spaces of palisade mesophyll cells. In addition, cupric stress induced changes in antioxidant enzyme activities. GPX (guaiacol peroxidase, EC 1.11.1.7) activity was decreased in 50 μM Cu-stressed leaves whereas 75 μM of CuSOP 4 resulted in an increase of enzyme activity. On the contrary, CAT (catalase, EC 1.11.1.6) activity was stimulated at 50 μM CuSO 4 but unaltered at 75 μM CuSO 4 . Transmission electron microscopy revealed that excess copper induced changes in the ultrastructure of chloroplasts visible in form of a deterioration in the grana structure and the accumulation and swelling of starch grains in the stroma.
In order to determine the toxic effect of chromium Cr(VI) on the seed germination, the root and shoot length, the root-cotyledonary leaves, the fresh and dry weight in eight-day-old seedlings Brassica oleracea L. var. acephala DC (kale) were treated with various concentrations of Cr in the growth medium. The accumulation of chromium in the tissues was determined in the cotyledons and the roots of the kale seedlings. High rate of Cr uptake was observed in the roots. But the organs could not accumulate large amount Cr. The effect of Cr on B. oleracea var. acephala was evaluated by changes in chlorophyll a, b, lipid peroxidation, proline, ascorbate, protein carbonyl groups, non-protein thiols and peroxidase activity. There were significant decreases in chlorophylls a, b content of the plants treated with Cr. Chromium treated kale seedlings had higher lipid peroxidation and the protein carbonyl groups in cotyledonary leaves than the roots. The changes refer to toxic effects of Cr. There were increases in the non-protein thiol, the total ascorbate, and proline content in the cotyledons and the roots of the seedlings grown on the media containing 0.1 and 0.15 mM Cr. The guaiacol peroxidase activity was higher in the roots of the seedlings than their cotyledons.
