模拟酸雨和Pb复合胁迫对2种草坪草生长及抗氧化生理的影响

[目的]探讨模拟酸雨和Pb复合胁迫对高羊茅(Festuca arundinacea Schreb.)和多年生黑麦草(Lolium perenne)生长及抗氧化生理的影响。[方法]通过盆栽试验研究了模拟酸雨(pH分别为3.5、4.5、5.6)和Pb(0、500、1 000、1 500 mg/kg)复合胁迫对高羊茅和黑麦草的生物量、叶绿素含量、丙二醛(MDA)含量以及超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、可溶性糖含量和电导率的影响。[结果]高羊茅和黑麦草生物量和叶绿素含量均随酸雨强度和Pb浓度的增加而下降,且在pH为3.5、Pb浓度为1 500 mg/kg时出现最低值;叶中SOD和POD活性均随Pb浓度和酸雨强度的增加而先升高后降低;MDA含量和可溶性糖含量以及电导率均随Pb浓度和酸雨强度的增加而逐渐升高,且在pH为3.5、Pb浓度为1 500 mg/kg时出现最大值。[结论]高羊茅和黑麦草通过调节抗氧化酶系统和提高可溶性糖含量来应对酸雨和Pb胁迫,但在高酸度酸雨和高浓度Pb复合胁迫下2种草坪草生长均受到明显抑制,在低酸度酸雨和低浓度Pb复合胁迫下高羊茅表现出相对较好的抗性。     

Both anti-oxidation and lipid-carbohydrate conversion enhancements are involved in priming-improved emergence of Echinacea purpurea seeds that differ in size

This study evaluated the effects of priming on emergence responses of purple coneflower (Echinacea purpurea L. Moench) seeds. The seeds that differ in seed size were either primed with moistened vermiculite (solid matrix priming) or primed in non-aerated −0.5 MPa polyethylene glycol 6000 solution at 25 °C for 6 days (osmopriming), followed by air-drying to their initial moisture level. The tetrazolium staining tests indicated that both large and small seeds were biochemically viable. No notable difference in germination percentage was found between large and small seeds. However, extensive cavity was visible in portions of small seeds in comparison with large seeds. Large seeds accumulated more antioxidants and had greater activities of anti-oxidative enzymes than small seeds. They also had greater isocitrate lyase and malate synthase activities than small seeds. As a result, large seeds had higher emergence percentage and faster emergence speed as compared to that of small seeds. Both solid matrix priming and osmopriming increased emergence percentage and shortened mean emergence time of purple coneflower seeds by increasing the activities of anti-oxidative enzymes and decreasing the levels of malondialdehyde and total peroxide accumulation. Moreover, priming also enhanced the anti-oxidative activities of treated seeds. The activities of isocitrate lyase and malate synthase were also increased in primed seeds. The enhanced anti-oxidation and lipid-carbohydrate conversion activities might explain in part why primed purple coneflower seeds emerged better than non-primed seeds.     

甲基紫精滴注法快速衡量香蕉抗氧化能力的初步试验

 滴注在香蕉(Musa paradisiaca var.sapientum)叶片表面上的甲基紫精(Methyl Viologen, 0.25 mmol·L^-1 )液滴，经过50 μmol·m^-2 ·s^-1 光照10 h，可在滴注位点周围形成明显的褐色损伤斑点。通过测定香蕉叶片主要抗氧化酶SOD和CAT活性，发现褐斑直径与SOD和CAT活性呈明显的负相关，说明甲基紫精褐斑直径与香蕉抗氧化能力之间具有密切的关系。外源活性氧处理引起的叶片膜脂过氧化损伤与甲基紫精褐斑直径呈正相关，表明利用甲基紫精滴注法快速衡量香蕉抗氧化能力的可行性。     

干旱及复水条件下转基因甘薯抗氧化防御系统特性

以转铜锌超氧化物歧化酶（Cu/Zn SOD）和抗坏血酸过氧化物酶（APX）基因甘薯(TS)及未转基因甘薯(NT)为实验材料,研究在旱后复水条件下转基因甘薯及未转基因甘薯抗氧化防御系统变化。结果显示,连续36h胁迫条件下,TS和NT的SOD活性都先降低后升高,但TS的SOD活性始终高于NT。胁迫至24h时,TS的SOD活性约为NT的1.2倍,复水后二者SOD活性都下降。持续胁迫时,TS的APX活性先升高后降低,NT与之相反,复水后TS和NT的APX活性都是先升高后降低,复水12h,TS的APX活性是NT1.5倍。在水分胁迫条件下,TS抗氧化物质AsA、CAR增长速度较快,复水后,TS中的AsA含量仍显著高于NT水分胁迫条件下TS的膜质受伤害程度要轻于NT,胁迫24h,复水12h,NT的MDA含量均约为TS的1.2倍。实验结果表明,同时转入SOD、APX抗氧化基因后,在胁迫及复水条件下转基因甘薯的抗氧化系统可以更好的对植株体进行保护及修复。     

Oxidative stress and antioxidative responses in plant–virus interactions

During plant–virus interactions, defence responses are linked to the accumulation of reactive oxygen species (ROS). Importantly, ROS play a dual role by (1) eliciting pathogen restriction and often localized death of host plant cells at infection sites and (2) as a diffusible signal that induces antioxidant and pathogenesis-related defence responses in adjacent plant cells. The outcome of these defences largely depends on the speed of host responses including early ROS accumulation at virus infection sites. Rapid host reactions may result in early virus elimination without any oxidative stress (i.e. a symptomless, extreme resistance). A slower host response allows a certain degree of virus replication and movement resulting in oxidative stress and programmed death of affected plant cells before conferring pathogen arrest (hypersensitive response, HR). On the other hand, delayed host attempts to elicit virus resistance result in an imbalance of antioxidative metabolism and massively stressed systemic plant tissues (e.g. systemic chlorotic or necrotic symptoms). The final consequence of these processes is a partial or almost complete loss of control over virus invasion (compatible infections).     

玉米苞叶中总黄酮提取及其体外抗氧化性能的研究

运用超声波技术提取玉米苞叶中的总黄酮,用亚硝酸钠-硝酸铝比色法测定总黄酮含量,得出玉米苞叶中总黄酮提取的最佳工艺条件:超声波功率700W,温度60℃,料液比(g/mL)1∶50,乙醇浓度为60%,提取时间为35min,玉米苞叶中总黄酮最大提取率为1.225%。体外抗氧化试验表明:玉米苞叶中的总黄酮对超氧阴离子自由基、羟基自由基清除能力较好,其IC50分别为1.5μg/mL左右和0.14mg/mL,清除能力均高于Vc;对DPPH自由基体系的清除率达到50%时,玉米苞叶中总黄酮的IC50为0.2mg/mL左右,Vc的IC50为0.075mg/mL,说明玉米苞叶中的总黄酮清除DPPH自由基的能力低于Vc,但在所选浓度剂量范围内,其最大清除率高于Vc。试验表明,玉米苞叶中的总黄酮是一种较好的天然自由基清除剂。     

自动自发气调箱贮藏对甜樱桃品质及抗氧化酶的影响

以艳阳樱桃为试材,研究了气调箱保鲜处理对甜樱桃果实贮藏品质变化的影响以及抗氧化酶的调控.结果表明:甜樱桃果实在贮藏30 d后,气调箱内CO2和O2体积分数分别维持在11％ ～ 12％和9％～10％.经气调箱贮藏的甜樱桃果实硬度在各个贮藏时期均高于对照果实,并且,它保持了果实中较高的维生素C含量,有效地延缓了可溶性固形物含量的下降,诱导了贮藏前期果实中过氧化物酶、过氧化氢酶、超氧化物歧化酶及抗坏血酸过氧化物酶活性.气调箱贮藏延缓了果实的pH值、花青素和总酚含量的升高.气调箱贮藏最明显的效果是降低了甜樱桃果实的病害发生率,在(0±0.5)℃贮藏60 d后仍具有较好的感官品质.     

Photochemical damage and comparative performance of superoxide dismutase and ascorbate peroxidase in sugarcane leaves exposed to paraquat-induced oxidative stress

The physiological responses of sugarcane (Saccharum officinarum L.) to oxidative stress induced by methyl viologen (paraquat) were examined with respect to photochemical activity, chlorophyll content, lipid peroxidation and superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities. Thirty-day-old sugarcane plants were sprayed with 0, 2, 4, 6 and 8 mM methyl viologen (MV). Chlorophyll fluorescence was measured after 18 h and biochemical analyses were performed after 24 and 48 h. Concentrations of MV above 2 mM caused significant damage to photosystem II (PSII) activity. Potential and effective quantum efficiency of PSII and apparent electron transport rate were greatly reduced or practically abolished. Both chlorophyll and soluble protein contents steadily decreased with MV concentrations above 2 mM after 24 h of exposure, which became more pronounced after 48 h, achieving a 3-fold decrease. Insoluble protein contents were little affected by MV. Oxidative stress induced by MV was evidenced by increases in lipid peroxidation. Specific activity of SOD increased, even after 48 h of exposure to the highest concentrations of MV, but total activity on a fresh weight basis did not change significantly. Nondenaturing PAGE assayed with H₂O₂ and KCN showed that treatment with MV did not change Cu/Zn-SOD and Mn-SOD isoform activities. In contrast, APX specific activity increased at 2 mM MV but then dropped at higher doses. Oxidative damage induced by MV was inversely related to APX activity. It is suggested that the major MV-induced oxidative damages in sugarcane leaves were related to excess H₂O₂, probably in chloroplasts, caused by an imbalance between SOD and APX activities, in which APX was a limiting step. Reduced photochemical activity allowed the early detection of the ensuing oxidative stress.     

丁香·厚朴不同溶剂萃取物的抑菌性和抗氧化性研究

[目的]研究丁香、厚朴不同溶剂萃取物的抑菌性和抗氧化性。[方法]利用石油醚、乙酸乙酯对丁香和厚朴的醇提物进行萃取,以食品中常见的8种腐败菌为试验菌种,采用纸片法研究各萃取相的抑菌性;用清除二苯代苦味肼基自由基（DPPH）法和Rancimat法研究各萃取相的抗氧化性。[结果]丁香的石油醚萃取液、厚朴的石油醚萃取液、乙酸乙酯萃取液对食品腐败常见的8种菌有较强的抑菌效果。各萃取液对DPPH自由基基均有较强的清除作用,但丁香的各萃取相提取物清除自由基能力均强于厚朴萃取相。各萃取液对猪油体系抗氧化能力的强弱依次为：厚朴乙酸乙酯萃取液〉厚朴石油醚萃取液〉丁香乙酸乙酯萃取液〉丁香石油醚萃取液〉丁香水萃取液〉厚朴水萃取液。[结论]该研究为开发天然食品防腐剂和抗氧化剂提供了科学依据。     

Antioxidative properties of partially purified barley hordein, rice bran protein fractions and their hydrolysates

Antioxidative properties of proteins from barley and rice bran and their hydrolysates were examined. Three major hordein fractions of barley, B, C and D hordeins, were partially purified by gel filtration. Albumin, globulin, prolamin and glutelin fractions of rice bran were fractioned by the Osborne method. Hydrolysates of these protein fractions were prepared by digesting with pepsin followed by trypsin. Antioxidant properties in terms of antioxidative activity against linoleic acid peroxidation and reducing activity without the lipid adjuvant were investigated. The globulin fraction from rice bran protein revealed the strongest antioxidative activity throughout the incubation time of 7 days (p ≤ 0.05). The albumin fraction of rice bran protein showed the highest reducing activity (6964 μmol of Fe²⁺) followed by globulin, prolamin, glutelin and hordein fractions with activities of 2904, 2017, 1809 and 1333 μmol of Fe²⁺, respectively (p ≤ 0.05). Partially purified C hordein exhibited the highest reducing activity compared with B and D hordeins. Protein hydrolysates obtained after digestion with pepsin and trypsin exhibited much greater antioxidative, as well as reducing, activities than those from before digestion.