Hydrogen peroxide pretreatment alters the activity of antioxidant enzymes and protects chloroplast ultrastructure in heat-stressed cucumber leaves

To elucidate the physiological mechanism of heat stress mitigated by exogenous hydrogen peroxide (H₂O₂) further, seedlings of Cucumis sativus cv Lvfeng no. 6 were subjected to two temperatures (42/38 and 25/18 °C) after pretreatment with 1.5 mM H₂O₂. We investigated whether exogenous H₂O₂ could protect chloroplast ultrastructure under heat stress (42/38 °C) and whether the protective effect was associated with the regulation of antioxidant enzymes. The heat condition disintegrated the membranes of 71.4% chloroplasts in the leaf cells and resulted in the elevated levels of malondialdehyde (MDA) and endogenous H₂O₂. When H₂O₂ pretreatment was combined with the heat stress, the abnormal chloroplasts occurred at a rate of 33.3%, and the contents of MDA and endogenous H₂O₂ were decreased. Heat stress and exogenous H₂O₂ both increased the activities of antioxidant enzymes such as glutathione peroxidase (GSH-Px, EC 1.11.1.9), dehydroascorbate reductase (DHAR, EC 1.8.5.1), monodehydroascorbate reducatase (MDHAR, EC 1.6.5.4), and glutathione reductase (GR, EC 1.6.4.2). The combined effect of heat stress and H₂O₂ pretreatment led to higher activity of antioxidant enzymes including superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), GSH-Px, DHAR, MDHAR and GR in comparison to the heat treatment alone. We propose that exogenous H₂O₂ increases antioxidant enzyme activities in cucumber leaves, decreases lipid peroxidation, and thus protects the ultrastructure of chloroplasts under heat stress.     

不同热激处理对菊花抗氧化相关酶活性的影响

以观赏菊花为试验材料,研究45℃胁迫3、5℃预热锻炼0、.5 mM水杨酸处理以及水处理对其叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶活性的影响。结果表明:3种酶活性均表现出下降的趋势,其中POD和CAT活性变化较为一致,与对照相比,下降程度从小到大依次为直接胁迫热激锻炼水处理水杨酸处理;而SOD下降程度从小到大则为热激锻炼直接胁迫水处理水杨酸处理。3种酶活性均表现为水杨酸处理的下降程度最大,且形态表现与生理变化一致。     

Physiological Responses of Wheat (Triticum Aestivum L.) –Aegilops Sharonensis Introgression Lines to Excess Copper

Two wheat lines (TL3 and TL5) derived from selection for Cu tolerance among wheat – Aegilops sharonensis hybrids were compared when grown as hydroponics at zero (control), 10⁻⁶ and 10⁻⁵  m CuSO₄. The morphometric measurements showed that the line TL5 with a more inhibited root system under 10⁻⁶  m CuSO₄ had a less inhibited shoot growth under 10⁻⁵  m CuSO₄ as compared to TL3. The decreased maximum efficiency of photosystem II and the more pronounced trend towards increased catalase activity suggested that despite the better shoot growth, the leaves of TL5 were more functionally injured. The increased content of carotenoids at excess Cu and the higher peroxidase and catalase activities of TL3 in control plants might contribute to its better stress tolerance. While no significant changes in enzyme activities were found at 10⁻⁶  m Cu, at 10⁻⁵  m the activities tended to increase. Although the close values of free phenolics concentrations in control plants, at Cu excess their content was higher in TL5 compared to TL3. The free phenolics content in roots at 10⁻⁶  m Cu decreased, and although higher at 10⁻⁵  m Cu, it remained below the control in TL3, and above the control in TL5. From the obtained results TL3 emerged to be more tolerant to excess Cu than TL5.     

禽甲状腺过氧化物酶活性的动态测定

正确测定甲状腺过氧化物酶 (TPO)的活性参照Hosoya提供的方法 ,对TPO活性的测定方法做了一定的改进 ,其准确度和精确度均有了一定的提高     

Selection parameters for resistance to Fusarium oxysporum f. sp. cubense race 1 and race 4 on diploid banana (Musa acuminata Colla)

Summary Shoot tip cultures from banana clones susceptible and resistant to Fusarium oxysporum f. sp. cubense (FOC) race 1 and race 4 were grown in vitro in the presence of different concentrations of fusaric acid and fungal crude filtrates or inoculated with a conidial suspension of FOC to assess correlation between in vivo and in vitro behaviour. Explants were susceptible to both filtrate and fusaric acid irrespective to their known field resistance/susceptibility response. No clear linkage between in vivo and in vitro behaviour was observed and our results suggest that the use of crude filtrate or non-host specific toxin (fusaric acid) in a screening programme for selecting a novel resistant genotype of Musa to FOC is not feasible. When peroxidase activity was used as a parameter to discriminate between sesceptibility and tolerance, results were in good agreement with field response of host plant to pathogens. Early enzymatic activity increased in the incompatible host-pathogen interaction but not in the compatible interaction.Abbreviations IBA Indolebutyric acid - 2iP 6-dimethylallylamino-purine - VCG Vegetative Compatibility Group - FOC Fusarium oxysporum f. sp. cubense - IEF isoelectrofocusing     

Production of an interspecific hybrid in Gypsophila by ovule-embryo culture

Summary We have succeeded in producing useful interspecific hybrid using ovule-embryo culture between Gypsophila paniculata L. Red Sea and G. manginii, an incompatible combination by ordinary cross breeding methods. The hybrid plant had double flowers with a color of pale purplish pink. Hybrid characteristics of the plant were firmed by observation of plant form, flower type, chromosome number and peroxidase isozyme patterns.     

变叶海棠（Malus toringoides）X陇东海棠（M.kansuensis）研究

对兼性无融合生殖种变叶海棠(3x)和陇东海棠(2x)的杂种实生苗进行了鉴别和矮化效应预测。结果表明,4x 杂种苗占65.2%,3x 母体苗占34.8%。杂种苗的酶谱可分为偏母型、互补型和突变型。互补型酶谱杂种苗的平均根皮率和叶片过氧化物酶活性显著高于偏母型酶谱杂种苗。选出的7株杂种单株,酶谱均属于互补型或突变型,表明陇东海棠的特征酶带20和21与其矮化效应有关。利用过氧化物酶同工酶谱可对该组合杂种苗的矮化效应作初步预测。     

水稻持久抗瘟性生化鉴定的研究

对２个持久抗瘟性和２个感病水稻品种苗期接种稻瘟菌，分析接种前后叶片内的生化指标，结果表明：接种后感病品种过氧化物酶活性持续增加，接种９６ｈ后酶活性急剧上升，而持抗品种过氧化物酶活性增幅较少．接种前后持抗和感病水稻品种叶片蛋白质含量变化均不明显，前者蛋白质含量显著高于后者．接种后０～６ｄ内持抗品种叶片可溶性糖含量均低于感病品种，而持抗品种游离氨基酸含量高于感病品种．初步认为：接种后叶片的过氧化物酶活性可作为鉴别水稻品种抗瘟性的依据     

新杀虫剂HNPC-A9908对蛋白核小球藻生理生化特性的影响

以蛋白核小球藻为材料，采用室内植物生长箱培养方法，研究了HNPC—A9908[O-(3一苯氧苄基)-2-甲硫基-1-(4-氯苯基)丙基酮肟醚]对小球藻细胞的致毒机理。结果表明，低浓度时HNPC—A9908对蛋白核小球藻蛋白质含量具有刺激增加的作用；随着浓度的加大，藻细胞蛋白质含量逐渐降低。同时藻细胞超氧化物歧化酶(SOD)和过氧化物酶(POD)活性也表现出类似的趋势，说明SOD和POD活性的降低打破了小球藻细胞内活性氧产生与清除之间的正常平衡状态，是HNPC—A9908造成藻细胞活性氧过量产生和积累，进而引起藻细胞膜脂过氧化伤害的主要原因之一