水淹对狗牙根营养繁殖植株的生理生态学效应

通过控制实验,测定了经过水淹处理的狗牙根营养繁殖体在恢复阶段的光合作用及其相关的生理生化指标的变化。结果显示,水淹时间对恢复阶段营养繁殖体的蒸腾作用和叶片温度的影响达到显著水平,水淹深度对该时期营养繁殖体的光合作用、气孔导度、胞间二氧化碳浓度和叶片温度有显著影响。水淹还导致了恢复期间植株叶片光合色素含量的显著变化。经过水淹的植株的各类光合色素含量以及色素总含量都显著高于对照植株,其中全淹处理的植株显著高于半淹处理的植株,叶绿素a与叶绿素b的比例也是全淹处理的植株显著高于半淹处理的植株。结果表明狗牙根营养繁殖体具有较强的恢复生长和生理活动的能力,是一种适宜于水电工程库区消落带生态恢复的物种。     

克隆整合有助于狗牙根抵御水淹

尽管国内外开展了大量的克隆整合对克隆植物抵御逆境能力影响的研究, 但整合对植物抵御水淹能力的影响研究仍比较缺乏。该文从克隆整合的角度探讨多年生草本植物狗牙根(Cynodon dactylon)对水淹胁迫的响应。试验模拟了先端分株(相对年幼的分株)分别处于0、5和15 cm三种水淹胁迫环境, 并在每个水淹梯度下实施先端分株与基端分株(相对年长的分株)之间匍匐茎连接或切断处理, 调查水淹一个月后基端分株和先端分株以及整个克隆片段在形态和生理上的表现。研究发现: 切断匍匐茎连接显著降低了狗牙根先端分株的生长, 表现在生物量下降、匍匐茎长度减短和分株数减少等方面; 水淹显著抑制了先端分株的生长, 但对基端分株的生长并未造成显著影响; 在5 cm水淹处理下, 匍匐茎保持连接时, 先端分株和整个克隆片段的生长显著增加; 连接或切断处理在不同水淹梯度下对匍匐茎平均节间长没有显著影响, 对先端分株或基端分株在光化学转化效率上也未表现显著性差异。结果表明: 克隆整合效应促进了狗牙根在水淹胁迫下分株的生长, 并有助于整个克隆片段抵御水淹胁迫。     

Reactive Oxygen Species Scavenging Enzymes and Down-Adjustment of Metabolism Level in Mitochondria Associated with Desiccation-Tolerance Acquisition of Maize Embryo

It is a well-known fact that a mature seed can survive losing most of its water, yet how seeds acquire desiccation-tolerance is not well understood. Through sampling maize embryos of different developmental stages and comparatively studying the integrity, oxygen consumption rate and activities of antioxidant enzymes in the mitochondria, the main origin site of reactive oxygen species (ROS) production in seed cells, we found that before an embryo achieves desiccation-tolerance, its mitochondria shows a more active metabolism, and might produce more ROS and therefore need a more effective ROS scavenging system. However, embryo dehydration in this developmental stage declined the activities of most main antioxidant enzymes and accumulated thiobarbituric acid-reactive products in mitochondria, and then destroyed the structure and functional integrity of mitochondria. In physiologically-matured embryos (dehydration-tolerant), mitochondria showed lower metabolism levels, and no decline in ROS scavenging enzyme activities and less accumulation of thiobarbituric acid-reactive products after embryo dehydration. These data indicate that seed desiccation-tolerance acquisition might be associated with down-adjustment of the metabolism level in the late development stage, resulting in less ROS production, and ROS scavenging enzymes becoming desiccation-tolerant and then ensuring the structure and functional integrity of mitochondria.     

Reactive Oxygen Species Scavenging Enzymes and Down-Adjustment of Metabolism Level in Mitochondria Associated with Desiccation-Tolerance Acquisition of Maize Embryo

It is a well-known fact that a mature seed can survive losing most of its water, yet how seeds acquire desiccation- tolerance is not well understood. Through sampling maize embryos of different developmental stages and comparatively studying the integrity, oxygen consumption rate and activities of antioxidant enzymes in the mitochondria, the main origin site of reactive oxygen species （ROS） production in seed cells, we found that before an embryo achieves desiccation-tolerance, its mitochondria shows a more active metabolism, and might produce more ROS and therefore need a more effective ROS scavenging system. However, embryo dehydration in this developmental stage declined the activities of most main antioxidant enzymes and accumulated thiobarbituric acid-reactive products in mitochondria, and then destroyed the structure and functional integrity of mitochondria. In physiologically-matured embryos （dehydration- tolerant）, mitochondria showed lower metabolism levels, and no decline in ROS scavenging enzyme activities and less accumulation of thiobarbituric acid-reactive products after embryo dehydration. These data indicate that seed desiccation- tolerance acquisition might be associated with down-adjustment of the metabolism level in the late development stage, resulting in less ROS production, and ROS scavenging enzymes becoming desiccation-tolerant and then ensuring the structure and functional integrity of mitochondria.     

Effect of lanthanum ions (La3+) on the reactive oxygen species scavenging enzymes in wheat leaves

Physiological effects of lanthanum ions on the activities of the enzymes in the reactive oxygen species (ROS) scavenging system in leaves of wheat (Triticum aestivum L.) seedlings were studied. Wheat leaves treated in Hogland solution with 0.1 mM LaCl₃ for 48 h showed increased levels of superoxide dismutase (SOD), catalase (CAT), ascorbate-specific peroxidase (AsA-POD), and dehydroascorbate reductase (DHAR). However, a minor effect was observed on the levels of monodehydroascorbate reductase (MDAR) and glutathione reductase (GR), which regulate the release of energy required by the ROS scavenging system. The whole system was linked up by H⁺ transmission. Our results indicated that the activities of the enzymes that function directly to remove ROS were elevated by La³⁺ treatment, which is consistent with the observations that La³⁺-treated plants had increased tolerance to environmental stresses. The remaining levels of MDAR and GR suggested that these two enzymes might be regulated differently from that of the other four enzymes studied.     

黄土丘陵区9种群落共存种干旱胁迫下抗氧化酶的响应

通过盆栽试验,以9种黄土丘陵区撂荒演替中期群落共存种(猪毛蒿、中华隐子草、小花棘豆、冰草、无芒隐子草、铁杆蒿、达乌里胡枝子、茭蒿和白羊草)为研究对象,测定其生长季中(8~10月)重度和中度干旱胁迫及适宜水分条件下(分别为45%~50%、60%~65%和75%~80%的田间持水量)活性氧清除酶(SOD、CAT、POD、APX)活性以及MDA含量的变化,分析土壤干旱程度、植物和生长季三因素对上述各生理指标的影响,研究群落共存种对土壤水分变化的响应,揭示水分变化后群落共存种的群体效应和植被演替的植物生理生态机制。结果表明:(1)9种群落共存种的SOD、CAT、POD、APX活性以及MDA含量存在显著的种间差异,生长季中(8~10月)以及不同水分条件下也存在显著差异。(2)达乌里胡枝子SOD活性、白羊草CAT活性、中华隐子草POD活性以及小花棘豆的CAT、POD和APX活性均相对较高,而且达乌里胡枝子的MDA含量较低;生长季中(8~10月)9种群落共存种的SOD、CAT和POD活性逐月下降且MDA含量进入10月后也有所下降,说明生长旺季耐旱性指标的生理活性较高;与POD和CAT活性相比,9种群落共存种的SOD和APX活性在重度干旱胁迫下显著提高,显示SOD和APX活性对于干旱胁迫具有较好的响应能力。(3)达乌里胡枝子和小花棘豆具有较高的SOD、APX活性和较低的MDA含量,说明达乌里胡枝子和小花棘豆的耐旱性相对较强,在土壤水分较低时,其在群落中的相对多度可能会有所上升。(4)9种群落共存种在演替序列上以前期种的SOD和APX活性相对较低,而演替后期种相对较高,表明演替后期的植物较为耐旱。     

三峡库区狗牙根对深淹胁迫的生理响应

选取三峡库区自然消落带野生狗牙根(XC)和非消落带野生狗牙根(FC)为研究对象,采用三重复裂区设计试验,主区为两品种,副区为6个不同深度水淹处理(0,1,2,5,10m和15m),分析了各处理植株几种酶活性和碳水化合物含量的变化情况.结果显示:①不同生境狗牙根受深淹胁迫后,丙二醛(MDA)都呈递增趋势,表明狗牙根在深淹胁迫下受到了不同程度的膜脂过氧化伤害,且随胁迫程度的增加受伤害增大.②超氧化物歧化酶(SOD)、过氧化物酶(POD)、谷胱甘肽还原酶(GR)活性和醇脱氢酶(ADH)活性较对照都有所增加;XC处理POD和SOD的最大值出现在5m深水淹处理,而FC出现在2m深处理,且XC 5米深淹处理GR值较对照和其他处理明显大;各受淹处理地下茎可溶性糖含量和淀粉含量都保持在较高水平.③从抗氧化酶活性和ADH活性的变化规律,以及淹水胁迫下植株的能量代谢情况,初步得出XC与FC都具有一定的耐淹性,且XC较FC具更耐深淹的能力,表明狗牙根作为禾本科植物遗传上具有一定的耐淹性,自然消落带狗牙根因长期生长于水淹胁迫环境,耐淹能力得到了进一步强化.从狗牙根对深淹胁迫的生理响应上,证明狗牙根是宜用于三峡水库消落带植被恢复的物种.     

养分异质条件下结缕草克隆分株生长、碳水化合物及可溶性蛋白的生理整合

通过对连接和断开的结缕草分株进行不同的养分处理,研究了养分异质条件下结缕草克隆分株生长、碳水化合物及可溶性蛋白含量的变化.结果表明: 在养分异质条件下,处于中、高养分水平的母株可以显著提高与其相连子株的地上、地下及总生物量,高养分下分别提高32.5%、22.1%和24.8%,降低根冠比、可溶性糖及非结构性碳水化合物(NSC)含量,高养分下分别降低7.7%、15.2%和13.1%,但是对淀粉、纤维素、可溶性蛋白含量无显著影响.处于中、高养分水平的子株对与其相连的母株生长、碳水化合物及可溶性蛋白含量没有显著影响.养分异质条件下结缕草母株对子株生物量、根冠比、可溶性糖及NSC含量有明显的生理整合,其整合强度与养分梯度呈正比,而对淀粉、纤维素及可溶性蛋白含量没有显现显著的生理整合效应.子株对母株各项指标都没有显著的生理整合,结缕草母株和子株间是一种单向的生理整合.     

活性氧清除系统对干旱胁迫的响应机制

干旱胁迫是影响植物生长发育的主要因子,干旱引起活性氧自由基增加,使植物细胞遭受氧化胁迫．植物体通过酶促和非酶促两大保护系统清除活性氧,活性氧自由基的变化也会引起抗氧化防御系统的不同变化．同时干旱胁迫下活性氧的产生也与ABA的积累、脯氨酸的积累以及叶绿素荧光猝灭密切相关,因此了解活性氧清除系统对干旱胁迫的响应机制以及活性氧在植物生理生化过程中的作用是非常必要的。     

Peroxisomal participation in the cellular response to the oxidative stress of endotoxin

Exposure to a sublethal dose of endotoxin offers protection against subsequent oxidative stresses. The cellular mechanisms involved in generating this effect are not well understood. We evaluated the effect of endotoxin on antioxidant enzymes in liver peroxisomes. Peroxisomes have recently been shown to contain superoxide dismutase (SOD) and glutathione peroxidase (GPX) in addition to catalase. Peroxisomes were isolated from liver homogenates by differential and density gradient centrifugations. Endotoxin treatment increased the specific activity of SOD and GPX in peroxisomes to 208% and 175% of control activity, respectively. These findings correlated with increases in peroxisomal SOD and GPX proteins observed by immunoblot. Although the quantity of catalase protein was increased when assessed by immunoblot analysis, the specific activity of catalase was decreased to 68% of control activity. Activation of catalase with ethanol only restored catalase activity to control levels suggesting that catalase had undergone irreversible inactivation. The observed increase in GPX activity may represent a compensatory mechanism triggered by accumulating H₂O₂. The data presented here suggest for the first time that mammalian peroxisomal antioxidant enzymes are altered during the oxidative injury of endotoxin treatment.     

涝渍胁迫下5种菊花近缘种属植物生理特性

采用土培模拟涝害的方法,对5种菊花近缘种属植物的根系活力、叶绿素含量和光合生理特性以及涝渍胁迫后的形态表现进行研究和观察,比较了其耐涝能力.结果表明:涝渍胁迫下,5种菊花近缘种属植物根系活力急剧下降,但紫花野菊在胁迫初期表现出强的根系活力;5种植物叶绿素含量总体呈现先升后降的趋势;涝渍胁迫15d时纪伊潮菊、泡黄金菊的光合强度明显降低,CO2同化作用下降,并出现负值,叶片已丧失光合作用能力,其次是大岛野路菊和那贺川野菊,而紫花野菊维持了一定水平的净光合速率.结合叶片外观形态观察发现,紫花野菊最为耐涝,泡黄金菊最不耐涝,而大岛野路菊、纪伊潮菊和那贺川野菊的耐涝性介于两者之间.     

高寒山区植物根抗氧化酶系统的季节变化与抗冷冻关系

在高寒山区（海拔2900m）和选取4种多年生草本植物,即无芒雀麦（Bromus inermis）、草地早熟禾（Poa sphyondylodes）、花誉麦（Bromus sinensis）和垂重申披碱草（Elymus nutans）,测定了秋末、冬初、冬季、春季气温变化过程中其根中丙二醛（MDA）含量和抗氧酶活力（过氧化氢酶（CAT）、过氧化物酶（POD）、超氧物歧化酶（SOD））和抗坏血酸氧化酶（APX）变化,分析了抗氧酶系统在根抗冷适应中的作用,结果表明,随秋末降温植物根中MDA含量增加,尔后下降,在冬季和翌年春季保持相对稳定。从9月初到10月下旬,4种植物根中SOD、CAT、POD活力平均增加170％、130％和56％。在冬季下降,但仍远高于9月,在春季气温上升过程中酶活力上升。根能在组织结冰状况下生存与其具备完善的保护酶系统,能及时清除氧自由基抑制膜脂过氧化维持膜完整性有关,据降温过程中MDA含量和抗氧酶活力变化,可将根冷适应分为两个阶段,即第1阶段平均气温在0℃以上,抗氧酶活力增强,MDA增加阶段,第2阶段平均气温降至0℃以下,最低气温降到－15℃以下,抗氧酶活力下降,MDA无明显变化阶段。     

Effects of Abscisic Acid and Water Stress on the Senescence of Detached Rice Leaves

The effects of abscisic acid (ABA) and water stress on senescence and enzyme activities of oxygen scavenging enzymes of detached rice leaves were compared. Exogenously applied ABA exhibited water stress-like effects by promoting senescence, by decreasing the activities of catalase, peroxidase, ascorbate peroxidase and superoxide dismutase. It seems that the effects of water stress on senescence and enzyme activities are possibly mediated through increased content of endogenous ABA. This revised version was published online in July 2006 with corrections to the Cover Date.     

The activity of recombinant human neuroglobin as an antioxidant and free radical scavenger

Free radicals are by-products of metabolism and exist in a homeostasis between generation and scavenging in vivo. Excessive free radicals cause various diseases, including nervous system diseases. Neuroglobin (Ngb), a nervous system-specific oxygen-binding protein, has been suggested to be a potential free radical scavenger in the nervous system in vivo; however, its underlying mechanism remains unclear. In this study, we investigated the antioxidant potential and free radical scavenging properties of recombinant human Ngb (rhNgb) in vitro. Interestingly, we found that the rhNgb protein itself has a direct and distinct antioxidant capacity and can efficiently scavenge a variety of free radicals, including the [2,2'-azino-di-(3-ethyl-benzthiazoline-6-sulfonic acid)] (ABTS) cation, superoxide anion, hydrogen peroxide, and hydroxyl radical. The capacity of rhNgb to scavenge the superoxide anion and hydrogen peroxide was even comparable to that of vitamin C. In addition, rhNgb had Fe(2+) chelating activity but hemoglobin did not. In conclusion, our results indicated that the rhNgb protein itself has antioxidant and free radical scavenging activities, providing fundamental evidence for the neuroprotective function of Ngb. These data provide key information for the origin of the neuroprotective and physiological role of Ngb and will promote the treatment of reactive oxygen species (ROS)-related diseases using this novel oxygen-binding globin.     

Effect of stationary magnetic field strengths of 150 and 200 mT on reactive oxygen species production in soybean

Our previous investigation reported the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean. In this study, soybean seeds treated with static magnetic fields of 150 and 200 mT for 1 h were evaluated for reactive oxygen species (ROS) and activity of antioxidant enzymes. Superoxide and hydroxyl radicals were measured in embryos and hypocotyls of germinating seeds by electron paramagnetic resonance spectroscopy and kinetics of superoxide production; hydrogen peroxide and antioxidant activities were estimated spectrophotometrically. Magnetic field treatment resulted in enhanced production of ROS mediated by cell wall peroxidase while ascorbic acid content, superoxide dismutase and ascorbate peroxidase activity decreased in the hypocotyl of germinating seeds. An increase in the cytosolic peroxidase activity indicated that this antioxidant enzyme had a vital role in scavenging the increased H(2)O(2) produced in seedlings from the magnetically treated seeds. Hence, these studies contribute to our first report on the biochemical basis of enhanced germination and seedling growth in magnetically treated seeds of soybean in relation to increased production of ROS.     

Antioxidant Systems in Ripening Tomato Fruits

Two cultivars of tomato (Lycopersicon esculentum Mill.), Selection-7 (shelf life 7–8 d) and ARTH-3 (shelf life 14–15 d) were analyzed for oxidative stress and the antioxidant enzyme system at different stages of fruit ripening. The results presented here suggest that during the early stages of fruit ripening, efficient antioxidant system protects the tomato fruits against the damaging effect of progressive oxidative stress. At later stages, however, oxidative damage occurs due to decreased activities of the ROS scavenging enzymes.     

Manipulation of oxidative stress responses as a strategy to generate stress-tolerant crops. From damage to signaling to tolerance

Plants exposed to hostile environmental conditions such as drought or extreme temperatures usually undergo oxidative stress, which has long been assumed to significantly contribute to the damage suffered by the organism. Reactive oxygen species (ROS) overproduced under stress conditions were proposed to destroy membrane lipids and to inactivate proteins and photosystems, ultimately leading to cell death. Accordingly, considerable effort has been devoted, over the years, to improve stress tolerance by strengthening antioxidant and dissipative mechanisms. Although the notion that ROS cause indiscriminate damage in vivo has been progressively replaced by the alternate concept that they act as signaling molecules directing critical plant developmental and environmental responses including cell death, the induction of genes encoding antioxidant activities is commonplace under many environmental stresses, suggesting that their manipulation still offers promise. The features and consequences of ROS effects depend on the balance between various interacting pathways including ROS synthesis and scavenging, energy dissipation, conjugative reactions, and eventually reductive repair. They represent many possibilities for genetic manipulation. We report, herein, a comprehensive survey of transgenic plants in which components of the ROS-associated pathways were overexpressed, and of the stress phenotypes displayed by the corresponding transformants. Genetic engineering of different stages of ROS metabolism such as synthesis, scavenging, and reductive repair revealed a strong correlation between down-regulation of ROS levels and increased stress tolerance in plants grown under controlled conditions. Field assays are scarce, and are eagerly required to assess the possible application of this strategy to agriculture.     

Scavenging of reactive oxygen species by some nonsteroidal anti-inflammatory drugs and fenofibrate

Ketoprofen and tolmetin are widely used nonsteroidal anti-inflammatory drugs, whereas fenofibrate belongs to a family of hypolipidemic drugs used in the prevention of cardiovascular diseases. The aim of this study was to assess effect of these drugs on reactions generating reactive oxygen species (ROS). The following generators of ROS were used: 18-crown-6/KO(2) dissolved in DMSO as a source of superoxide radical (O(.-)(2), the Fenton-like reaction (Cu/H(2)O(2)) for hydroxyl radical (HO(.)), 2,2'-azobis (2-amidino-propane) dichloride (AAPH) as peroxyl radical (ROO(.)) generator, and a mixture of alkaline aqueous H(2)O(2) and acetonitrile for singlet oxygen ((1)O(2)). Measurements were done using chemiluminescence, fluorescence, and spin-trapping with 2,2,6,6-tetramethylpiperidine combined with electron spin resonance spectroscopy (ESR), and a deoxyribose assay based on the spectrophotometry. The results obtained demonstrated that all tested drugs were active against O(.-)(2). There was a clear ranking of drug inhibition effects on chemiluminescence from the O(.-)(2) system: ketoprofen > tolmetin > fenofibrate. The examined compounds inhibited the HO(.)-dependent deoxyribose degradation and scavenged the ROO(.) concentration dependently with an order of potencies similar to that of the superoxide radical system. Hence, these results indicate that the studied drugs show broad ROS scavenging property and, as a consequence, might decrease tissue damage due to the ROS and thus to contribute to anti-inflammatory therapy.     

养分异质条件下结缕草克隆分株生长及光合作用的生理整合

通过对连接和断开的分株进行不同养分处理,研究养分异质条件下结缕草克隆分株生长及光合作用的变化.结果表明:在养分异质条件下,处于中、高养分水平的母株可以提高与其相连子株的叶长、叶宽、根质量、叶质量、光合速率、气孔导度、蒸腾速率和水分利用效率,高养分条件下分别提高16.0%、8.3%、24.4%、58.1%、30.3%、54.0%、9.2%和21.9%,降低根冠比和胞间CO2浓度,在高养分下分别降低21.6%和31.5%;处于中、高养分水平的子株对与其相连母株的生长及光合特性没有显著影响.在养分异质条件下,结缕草母株对子株存在生理整合,养分梯度越大,整合强度越强.结缕草克隆子株可以从母株获益,但母株不能从子株获益,子株是生理整合单向获益者.