硝酸银对雌性黄瓜植株三种氧化酶同工酶的影响

雌性黄瓜植株经硝酸银处理后其茎尖和真叶过氧化物酶活性极显著地增加,茎尖24小时、真叶36小时酶活性达到最大值,分别增加了178.2%和284.6%,随后酶活性逐渐下降,但酶活性仍然较对照植株高。多酚氧化酶和超氧化物歧化酶的同工酶活性也增加。同时硝酸银能诱发黄瓜植株过氧化物酶、多酚氧化酶和超氧化物歧化酶产生新的同工酶, 用等电聚焦更能有效地观察新产生的同工酶。     

黄瓜植株性别表现与3种氧化酶同工酶的关系

采用同工酶电泳技术分析了二叶期纯雌株和雌雄株黄瓜（Ｃｕｃｕｍｉｓ ｓａｔｉｖｕｓ Ｌ．）子叶和真叶过氧化物酶、多酚氧化酶和超氧化物歧化酶同工酶,结果发现：给株比雌雄株酶活性强、酶带数量多,这种差异酶带大多与雌性或雌雄性别紧密相关,经检验可以作为黄瓜雌性株早期鉴定的生化标记,尤其以真叶中多酚氧化酶同工酶Ｒｆ０．２８７表现稳定,鉴定成功率高。等电聚焦电泳垂直平板聚丙烯酰胺凝胶电泳分辨效果好。     

红豆杉组织培养中SINENXANS高产细胞系Ts19的几种同工酶动态比较研究

对从中国红豆杉的茎来源的愈伤组织经筛选而得的ｓｉｎｅｎｘａｎｓ高产细胞系Ｔｓ１９的过氧化物酶（ＰＯＤ）、酯酶（ＥＳＴ）、细胞色素氧化酶（ＣＯＤ）、淀粉酶（ＡＭＬ）、多酚氧化酶（ＰＰＯ）及超氧化物歧化酶（ＳＯＤ）的同工酶,可溶性蛋白的含量及电泳谱带、超氧化物歧化酶、多酚氧化酶和苯丙氨酸解氨酶（ＰＡＬ）的活性作了比较研究。并与培养过程中ｓｉｎｅｎｘａｎｓ含量的动态变化相比较,探索了这几种同工酶的酶谱和两种酶活性与ｓｉｎｅｎｘａｎｓ的生物合成的关系。旨在为建立紫杉醇生物合成的中间代谢模型奠定基础。     

红豆杉组织培养中SINENXANS高产细胞系Ts19的几种同工酶动态比？…

对从中国红豆杉的茎来源的愈伤组织经筛选而得的ｓｉｎｅｎｘａｎｓ高产细胞系Ｔｓ１９的过氧化物酶（ＰＯＤ）、酯酶（ＥＳＴ）、细胞色素氧化酶（ＣＯＤ）、淀粉酶（ＡＭＬ）、多酚氧化酶（ＰＰＯ）及超氧化物歧化酶（ＳＯＤ）的同工酶,可溶性蛋白的含量及电泳谱带、超氧化物歧化酶、多酚氧化酶和苯丙氨酸解氨酶（ＰＡＬ）的活性作了比较研究。并与培养过程中ｓｉｎｅｎｘａｎｓ含量的动态变化相比较,探索了这几种同工酶的酶谱和     

几种氧化酶活性与植物对二氧化硫抗性的研究——植物本底及受污染后酶活性大小与抗性的关系

对27种不同抗性等级植物本底(未经污染处理的正常植物)多酚氧化酶、抗坏血酸氧化酶和过氧化物酶活性测定结果,植物本底多酚氧化酶活性与抗性有呈负相关的趋势,抗坏血酸氧化酶和过氧化物酶活性大小与抗性不具规律性。 对植物受不同浓度SO_2污染后酶活性变化分析结果看出,蚬木(抗性植物)和汗斑草(敏感植物)在浓度达受阈前,多酚氧化酶、抗坏血酸氧化酶和过氧化物酶均有随浓度的升高而酶活性逐渐增大的趋势,仅是不同的酶其活性高峰在不同浓度梯度中出现迟早不同而己。在污染浓度达受伤阈后,随着浓度的继续增大,酶活性逐渐下降。而白蝉(抗性植物)和大猪屎青(敏感植物)有的酶具有规律性,有的酶不具有这种规律性。 用使可见伤害达50％的SO_2污染汗斑草后4小时(一次污染),过氧化物酶活性为0.34(未受污染的为12.69),仅为未受污染的2.68％,降低了97.32％,但24小时后为7.68,为未受污染的60.52％,比受污染后4小时提高了57.84％,72小时后为8.52,为未受污染的67.13％,比受污染后4小时提高了65.45％。多酚氧化酶亦具有这种规律性。说明二氧化硫对这两种酶的抑制作用是可逆的。     

诱抗菌激发子诱导黄瓜产生对炭疽病的抗性

用细胞壁提取法从诱抗菌中提取出激发子,经点滴法测定发现该激发子与活菌一样能诱导黄瓜产生对炭疽病的抗性反应。黄瓜经激发子处理后,体内与抗病反应有关的过氧化物酶、多酚氧化酶和苯丙氨酸解氨酶活性显著增强;过氧化物酶同功酶酶带增多,着色加深;酚类物质和木质素含量也明显提高。     

诱抗菌激发子诱导黄瓜产生对炭疽病的抗性

用细胞壁提取法从诱抗菌中提取出激发子,经点滴法测定发现该激发子与活菌一样能诱导黄瓜产生对炭疽病的抗性反应。黄瓜经激发子处理后,体内与抗病反应有关的过氧化物酶、多酚氧化酶和苯丙氨酸解氨酶活性显著增强;过氧化物酶同功酶酶带增多,着色加深;酚类物质和木质素含量也明显提高。     

光合菌对黄瓜光合及抗氧化同工酶的影响

以2种基因型的黄瓜(Cucumis sativus)为材料, 研究光合菌(PSB)的喷施对植物生物量、净光合速率(Pn)、叶片PSII 的最大光化学效率(Fv/Fm)及抗氧化同工酶代谢的影响。结果表明, 喷施PSB均能诱导2种基因型黄瓜的生物量显著增加, 并伴随Pn的显著提高。但是, 2种基因型黄瓜的Fv/Fm并不受PSB喷施的影响; PSB能使总过氧化物歧化酶(SOD)和抗坏血酸过氧化酶(APX)活性提高, 并使它们的多数同工酶的活性上调, 这些同工酶活性的增加在叶绿体中表现更为明显(如 Cu/Zn-SOD、Fe-SOD 和 sAPX)。研究结果表明, PSB能通过增强黄瓜抗氧化酶体系的活性改善植株的抗氧化能力, 从而在植株的生长和光合作用方面起到促进作用。     

光合菌对黄瓜光合及抗氧化同工酶的影响

以2种基因型的黄瓜（Cucumis sativus）为材料,研究光合菌（PSB）的喷施对植物生物量、净光合速率（Pn）、叶片PSII的最大光化学效率（Fv／Fm）及抗氧化同工酶代谢的影响。结果表明,喷施PSB均能诱导2种基因型黄瓜的生物量显著增加,并伴随Pn的显著提高。但是,2种基因型黄瓜的Fv/Fm并不受PSB喷施的影响：PSB能使总过氧化物歧化酶（soo）和抗坏血酸过氧化酶（APX）活性提高,并使它们的多数同工酶的活性上调,这些同工酶活性的增加在叶绿体中表现更为明显（如Cu／Zn-SOD、Fe-SOD和sAPX）。研究结果表明,PSB能通过增强黄瓜抗氧化酶体系的活性改善植株的抗氧化能力,从而在植株的生长和光合作用方面起到促进作用。     

壳寡糖诱导黄瓜抗黄瓜黑星病的初步研究

本文研究了壳寡糖诱导黄瓜对黑星病的抗性作用。利用6 mg/mL壳寡糖溶液对苗期黄瓜诱导,进行病情调查统计及测定处理前后黄瓜叶片的主要防御酶系———苯丙氨酸解氨酶,过氧化物酶,多酚氧化酶,超氧化物歧化酶,过氧化氢酶的活性变化。结果显示,壳寡糖对黄瓜黑星病在10 d和17 d的诱抗效果分别为60.25%和47.59%,且作为诱导因子可显著提高黄瓜叶片内苯丙氨酸解氨酶(PAL)活性,过氧化物酶(POD)、多酚氧化酶(PPO)、超氧化物歧化酶(SOD)活性也有所提高,但叶片内过氧化氢酶(CAT)活性无较明显变化。研究结果表明壳寡糖对黄瓜抗黑星病产生诱导作用,为研究壳寡糖作为新型生物农药提供了依据。     

Early effects of boron deficiency on indoleacetic Acid oxidase levels of squash root tips

The indoleacetic acid (IAA) oxidase activity of root tips of boron-sufficient, -deficient, recovering, and IAA-treated boron-sufficient squash plants (Cucurbita pepo L.) was determined. Apical and subapical root sections displayed an increase in IAA oxidase activity between 6 and 9 hours after boron was withheld, and after 24 hours the activity of the apical sections showed a 20-fold increase over +B controls. Root elongation of -B plants was inhibited before an increase in oxidase activity could be detected. Roots of plants subjected to 12 hours of -B treatment and then transferred to +B treatment for recovery regained normal elongation rates and oxidase activity within 18 to 20 hours. IAA treatment of +B plants increased IAA oxidase activity of apical and subapical root sections and also inhibited root elongation and caused symptoms similar to -B treatments.     

Appearance of peroxidase isozymes in floral‐initiated shoot apices of Pharbitis nil

A novel biochemical assay system for detecting the early stage of flowering is reported. Peroxidase isozymes in shoot apices of Pharbitis nil plants that had been exposed to flower‐inducing or non‐inducing conditions were analyzed by isoelectric focusing in polyacrylamide gels and activity staining for peroxidase. Several isozymes with pH 8.5–8.8 appeared for the first time 7 days after the beginning of short‐day treatment, but not after nightbreak (non‐inducing) treatment. When shoot tips were cultured in vitro, these same isozymes also appeared after short‐day treatment but not after night‐break treatment. The extent of the appearance of these isozymes was reduced by exposure to high or low temperature during the inductive dark period and removal of cotyledons after the inductive dark period. Such treatments also reduced the extent of flowering. The appearance of an isozyme with pH 8.5 was more closely correlated with flowering than that of the other isozymes. From these results, the appearance of this peroxidase isozyme in shoot apices is discussed as a biochemical marker of flowering in intact plants and in cultured shoot tips.     

Thermoinductive Regulation of Gibberellin Metabolism in Thlaspi arvense L. (II. Cold Induction of Enzymes in Gibberellin Biosynthesis)

Vernalization of Thlaspi arvense L. results in the alteration of gibberellin (GA) metabolism such that the metabolism and turnover of the GA precursor ent-kaur-16-en-19-oic acid (kaurenoic acid) is dramatically increased. This cold-induced change in GA metabolism is restricted to the shoot tip, the site of perception of cold in this species (J.P. Hazebroek, J.D. Metzger [1990] Plant Physiol 94: 157-165). In the present report additional biochemical information about the nature of this low-temperature-regulated process is provided. The endogenous levels of kaurenoic acid in leaves and shoot tips of plants were estimated by combined gas chromatography-chemical ionization mass spectrometry at various times after 4 weeks of vernalization at 6[deg]C. The endogenous levels in shoot tips declined 10-fold by 2 d after the plants were returned to 21[deg]C; this decline continued such that there was nearly 50-fold less kaurenoic acid by 10 d after the end of vernalization. No effect of vernalization on the endogenous levels of kaurenoic acid in leaves was observed. An in vitro enzyme assay was developed to monitor changes in the ability of tissues to convert kaurenoic acid to ent-7[alpha]-hydroxykaur-16-en-19-oic acid (7-OH kaurenoic acid). The activity of this enzyme rapidly increased in microsomal extracts from shoot tips following the end of vernalization. No thermoinduced increase in activity was observed in leaves. The enzymic oxidation of ent-kaurene to ent-kaurenol was also induced in shoot tips by vernalization. However, this reaction does not appear to be rate limiting for GA biosynthesis, because substantial amounts of kaurenoic acid accumulated in noninduced shoot tips. These results corroborate our hypothesis that the conversion of kaurenoic acid to 7-OH kaurenoic acid is the primary step in GA metabolism regulated by vernalization in Thlaspi shoot tips.     

Peroxidase Activity in the Abscission Zone of Bean Leaves during Abscission

Peroxidase activity and localization in the abscission zone of bean leaves were studied histochemically and by gel electrophoresis. Deblading of bean leaves resulted in an increase in peroxidase activity in the abscission zone 2 to 4 days after deblading with highest activity just prior to separation. In debladed plants, the cell division in six to eight layers of cells preceded separation. An ethylene treatment (8 microliters per liter) induced separation of debladed petioles in approximately 24 hours and of intact plants in 36 to 48 hours. Ethylene treatment produced similar results in both debladed and intact plants. In ethylene-treated plants, whether debladed or not, enzyme localization was restricted to only two to three layers of cells with no cell division apparent prior to separation. Infrequent cell divisions were observed after treatment with 2-chloroethylphosphonic acid (1000 micrograms per liter) (Ethephon); however, other changes were similar to those observed with ethylene. Deblading and ethylene treatment resulted in changes in the six peroxidase isozymes observed in the abscission zone. Only four were observed in samples collected 2 centimeters below the abscission zone. Peroxidase bands IV and V increased significantly in debladed and ethylene-treated plants and peroxidase VI decreased only in debladed plants. The changes in peroxidase activity were invariably observed prior to separation in all treatments.     

Biochemical and phenotypical characterization of transgenic tomato plants overexpressing a basic peroxidase

Tomato plants ( Lycopersicon esculentum Mill. cv. Pera) were transformed via Agrobacterium tumefaciens with the binary vector pKYLX71 containing a tomato basic peroxidase (EC 1.11.1.7) gene, tpx1 , under the control of the cauliflower mosaic virus (CaMV35S) promoter. Transgenic plants showed a 2–5-fold increase in the activity of the peroxidase ionically bound to the cell wall, whereas soluble peroxidase activity remained similar or even lower than wild-type plants. Isoelectric focusing showed the presence of a new isoperoxidase of pI ca 9 in the ionically bound extract. Western blot also showed the presence of a new band at 41 kDa that was absent in the wild-type extract. A 40–220% increment of lignin content of the leaf was found in transgenic plants. Shoot phenotype of transgenic plants was similar to wild type, although under stress, the plants appeared wilted and the new leaves had a reduced area and were thicker than wild-type or older transgenic leaves. The root system was underdeveloped in transgenic plants, but the rooting ability of the stem was not affected by the overexpression of peroxidase. Finally, the morphogenetic response of cotyledon and hypocotyl explants from transgenic plants was evaluated. In the case of cotyledons, the percentage of explants with shoot was not different from wild-type plants. For hypocotyl, one of the transgenic lines showed a 30% reduction in the percentage of shoot organogenesis. The results are discussed in relation to the role of tpx1 in lignin synthesis.     

Peroxide Levels and the Activities of Catalase, Peroxidase, and Indoleacetic Acid Oxidase during and after Chilling Cucumber Seedlings

The activities of catalase, peroxidase, indoleacetic acid (IAA) oxidase and peroxide levels in cucumber plants during and after chilling were determined. During 96 hours at 5 C and 85% relative humidity, catalase activity declined, IAA oxidase activity increased, and peroxide concentrations increased. Peroxidase activity was not affected by chilling. When chilled plants were returned to 25 C to recover, enzyme activities and peroxide concentration were restored to their prechilling levels. The increase in peroxide and IAA oxidase activity may inactivate or destroy IAA and thus retard growth.     

Effect of drought on sorbitol and sucrose metabolism in sinks and sources of peach

In peach (Prunus persica [L.] Batsch.), sorbitol and sucrose are the two main forms of photosynthetic and translocated carbon and may have different functions depending on the organ of utilization and its developmental stage. The role and interaction of sorbitol and sucrose metabolism was studied in mature leaves (source) and shoot tips (sinks) of ‘Nemaguard’ peach under drought stress. Plants were irrigated daily at rates of 100, 67, and 33% of evapotranspiration (ET). The relative elongation rate (RER) of growing shoots was measured daily. In mature leaves, water potential (Ψ_w), osmotic potential (Ψ_s), sorbitol‐6‐phosphate dehydrogenase (S6PDH, EC 1.1.1.200), and sucrose‐phosphate synthase (SPS, EC 2.4.1.14) activities were measured weekly. Measurements of Ψ_s, sorbitol dehydrogenase (SDH, 1.1.1.14), sucrose synthase (SS, EC 2.4.1.13), acid invertase (AI, EC 3.2.1.26), and neutral invertase (NI, EC 3.2.1.27) activities were taken weekly in shoot tips. Drought stress reduced RER and Ψ_w of plants in proportion to water supply. Osmotic adjustment was detected by the second week of treatment in mature leaves and by the third week in shoot tips. Both SDH and S6PDH activities were reduced by drought stress within 4 days of treatment and positively correlated with overall Ψ_w levels. However, only SDH activity was correlated with Ψ_s. Among the sucrose enzymes, only SS was affected by drought, being reduced after 3 weeks. Sorbitol accumulation in both mature leaves and shoot tips of stressed plants was observed starting from the second week of treatment and reached up to 80% of total solutes involved in osmotic adjustment. Sucrose content was up to 8‐fold lower than sorbitol content and accumulated only occasionally. We conclude that a loss of SDH activity in sinks leads to osmotic adjustment via sorbitol accumulation in peach. We propose an adaptive role of sorbitol metabolism versus a maintenance role of sucrose metabolism in peach under drought stress.     

Changes in the Activity of Antioxidant Enzymes in Wheat Leaves and Roots as a Function of Nitrogen Source and Supply

The activity of enzymes participating in the systems of antioxidant protection was assayed in the second leaf and roots of 21-day-old wheat seedlings (Triticum aestivum L.) grown in a medium with nitrate (NO^– ₃ treatment), ammonium (NH⁺ ₄ treatment), or without nitrogen added (N-deficiency treatment). The activities of superoxide dismutase (SOD), peroxidase, ascorbate peroxidase, glutathione reductase, and catalase in the leaves and roots of the NH⁺ ₄ plants was significantly higher than in the plants grown in the nitrate medium. The activity of SOD decreased and ascorbate peroxidase markedly increased in leaves, whereas the activity of ascorbate peroxidase increased in the roots of N-deficient plants, as compared to the plants grown in nitrate and ammonium. Low-temperature incubation (5°, 12 h) differentially affected the antioxidant activity of the studied plants. Whereas leaf enzyme activities did not change in the NH⁺ ₄ plants, the activities of SOD, peroxidase, ascorbate peroxidase, and catalase markedly increased in the NO^– ₃ plants. In leaves of the N-deficient plant, the activity of SOD decreased; however, the activity of other enzymes increased. In response to temperature decrease, catalase activity increased in the roots of NO^– ₃ and NH⁺ ₄-plants, whereas in the N-deficient plants, the activity of peroxidase increased. Thus, in wheat, both nitrogen form and nitrogen deficiency changed the time-course of antioxidant enzyme activities in response to low temperature.