Response of barley grains to the interactive e.ect of salinity and salicylic acid

Effect of grain soaking presowing in 1 mM salicylic acid (SA) and NaCl (0, 50, 100, 150 and 200 mM) on barley (Hordeum vulgare cv Gerbel) was studied. Increasing of NaCl level reduced the germination percentage, the growth parameters (fresh and dry weight), potassium, calcium, phosphorus and insoluble sugars content in both shoots and roots of 15-day old seedlings. Leaf relative water content (RWC) and the photosynthetic pigments (Chl a, b and carotenoids) contents also decreased with increasing NaCl concentration. On the other hand, Na, soluble sugars, soluble proteins, free amino acids including proline content and lipid peroxidation level and peroxidase activity were increased in the two plant organs with increasing of NaCl level. Electrolyte leakage from plant leaves was found to increase with salinity level. SA-pretreatment increased the RWC, fresh and dry weights, water, photosynthetic pigments, insolube saccharides, phosphorus content and peroxidase activity in the stressed seedlings. On the contrary, Na⁺, soluble proteins content, lipid peroxidation level, electrolyte leakage were markedly reduced under salt stress with SA than without. Under stress conditions, SA-pretreated plants exhibited less Ca²⁺ and more accumulation of K⁺, and soluble sugars in roots at the expense of these contents in the plant shoots. Exogenous application (Grain soaking presowing) of SA appeared to induce preadaptive response to salt stress leading to promoting protective reactions to the photosynthetic pigments and maintain the membranes integrity in barley plants, which reflected in improving the plant growth.     

Salicylic acid-induced inactivation of creatine kinase in the presence of lactoperoxidase and H2O2

To clarify one mechanism of aspirin-induced gastric mucosal damage, inactivation of creatine kinase (CK) by salicylic acid that is easily produced from aspirin in vivo was examined in the presence of lactoperoxidase (LPO) and H2O2 (LPO-H2O2). Salicylic acid inactivated CK (rabbit muscle) during its interaction with LPO-H2O2. CK activity in gastric mucosal homogenate decreased dependent on the concentration of salicylic acid in the presence of LPO-H2O2. Oxygen radical scavengers did not prevent the inactivation of CK. Direct detection of free radicals of salicylic acid by electron spin resonance was unsuccessful. However, glutathionyl radicals were formed during the interaction of salicylic acid with LPO-H2O2 in the presence of reduced glutathione and 5,5-dimethyl-1-pyrroline oxide as a spin trap agent. Among salicylic acid-related drugs, salsalate, but not aspirin and ethenzamide, inactivated CK, indicating the phenolic hydroxyl group is oxidized by LPO-H2O2. During oxidation of salicylic acid by LPO-H2O2, the sulfhydryl group in CK markedly decreased, and salicylic acid bound to CK. These results indicate that CK was inactivated through loss of the sulfhydryl group and binding of salicylic acid.     

Effects of peroxidase substrates on the Amplex red/peroxidase assay: antioxidant properties of anthracyclines

Oxidation of Amplex red (AR) by H(2)O(2) in the presence of horseradish peroxidase (HRP) gives rise to an intensely colored product, resorufin. This reaction has been frequently employed for measurements of low concentrations of H(2)O(2) in biological samples. In the current study, we show that alternative peroxidase substrates, such as p-hydroquinone, acetaminophen, anticancer mitoxantrone, and ametantrone, inhibit AR oxidation by consuming H(2)O(2) in a competitive process. In contrast, the anthracycline agents doxorubicin, daunorubicin, and 5-iminodaunorubicin are markedly less efficient as competitors in these reactions, as is salicylic acid. When [H(2)O(2)]>[AR], the generated resorufin was oxidized by HRP and H(2)O(2). In the presence of anthracyclines, this process was inhibited and occurred with a lag time, the duration of which depended on the concentration of anthracycline. We propose that the mechanism of this inhibition is due to the antioxidant activity of anthracyclines involving the reduction of the resorufin-derived phenoxyl radical by the drugs' hydroquinone moiety back to resorufin. In addition to HRP, lactoperoxidase, myeloperoxidase, and HL-60 cells, naturally rich in myeloperoxidase, also supported these reactions. Results of this study suggest that extra caution is needed when using AR to measure cellular H(2)O(2) in the presence of alternative peroxidase substrates. They also demonstrate that the anticancer anthracyclines may function as antioxidants.     

Thermotolerance and Related Antioxidant Enzyme Activities Induced by Heat Acclimation and Salicylic Acid in Grape (Vitis vinifera L.) Leaves

Thermotolerance and related antioxidant enzyme activities induced by both heat acclimation and exogenous salicylic acid (SA) application were studied in grapevine (Vitis vinifera L. cv. Jingxiu). Heat acclimation and exogenous SA application induced comparable changes in thermotolerance, ascorbic acid (AsA), glutathione (GSH), and hydrogen peroxide (H₂O₂) concentrations, and in activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), ascorbic peroxidase (APX) and catalase (CAT) in grape leaves. Within 1 h at 38 °C, free SA concentration in leaves rose from 3.1 μg g⁻¹ FW to 19.1 μg g⁻¹ FW, then sharply declined. SA application and heat acclimation induced thermotolerance were related to changes of antioxidant enzyme activities and antioxidant concentration, indicating a role for endogenous SA in heat acclimation in grape leaves.     

Salicylic acid-induced adaptive response to copper stress in sunflower (Helianthus annuus L.)

The ameliorative effect of salicylic acid (SA: 0.5 mM) on sunflower (Helianthus annuus L.) under Cu stress (5 mg l⁻¹) was studied. Excess Cu reduced the fresh and dry weights of different organs (roots, stems and leaves) and photosynthetic pigments (chlorophyll a, b and carotenoids) in four-week-old plants. There was a considerable increase in Chl a/b ratio and lipid peroxidation in both the roots and leaves of plants under excess Cu. Soluble sugars and free amino acids in the roots also decreased under Cu stress. However, soluble sugars in the leaves, free amino acids in the stems and leaves, and proline content in all plant organs increased in response to Cu toxicity. Salicylic acid (SA) significantly reduced the Chl a/b ratio and the level of lipid peroxidation in Cu-stressed plants. Under excess Cu, a higher accumulation of soluble sugars, soluble proteins and free amino acids including proline occurred in plants treated with 0.5 mM SA. Exogenous application of SA appeared to induce an adaptive response to Cu toxicity including the accumulation of organic solutes leading to protective reactions to the photosynthetic pigments and a reduction in membrane damage in sunflower.     

水杨酸和茉莉酸甲酯对丹参幼苗叶片显微结构、光合及非结构糖积累的影响

研究了水杨酸(SA)和茉莉酸甲酯(MeJA)处理对丹参(Salvia miltiorrhiza Bunge)幼苗叶片显微结构、叶片光合能力及幼苗中非结构糖积累的影响.结果显示:SA处理增加了丹参幼苗叶片气孔密度;叶肉细胞排列紧密、体积减小,叶肉细胞内叶绿体数目减少,但叶绿体体积增大,叶绿体基粒片层结构的数目增加;叶片中叶绿素a、b含量、叶气孔导度、蒸腾速率以及净光合速率均增加;同时,幼苗根中和叶片中酸性转化酶活性降低,幼苗地上部分蔗糖含量及可溶性糖总量显著高于对照.MeJA处理减少了叶片气孔密度,气孔发育畸形;叶肉细胞间隙增大,栅栏细胞层数减少,叶肉细胞内叶绿体数目减少,叶绿体体积减小,叶绿体基粒片层结构被破坏;叶片中叶绿素a及类胡萝卜素含量、叶片的净光合速率低于对照,叶气孔导度、蒸腾速率增强;同时,幼苗根中及叶中酸性转化酶活性增加,幼苗根中蔗糖含量及可溶性糖总量显著低于对照.可见,SA处理能促进植物叶片显微结构发育,增强叶片光合能力,抑制蔗糖降解并促进蔗糖积累;而MeJA处理则破坏了植物叶片显微结构,降低了叶片光合能力,促进了蔗糖降解并减少蔗糖积累.