UV-B辐射对蚕豆叶膜脂过氧化的影响及其机制

温室种植的吞豆在0（CK）,8．82kJ/m2(T1)和12．6kJ/m2(T2)3种剂量的紫外线B（UV－B）辐射引起膜脂变化及其机制的研究结果表明,UV0B处理后,蚕豆叶片中丙二醛（MDA）和H2O2含量升高,膜脂肪酸不饱和度指数（IUFA）降低,脂氧合酶（LOX）活性升高,超氧歧化酶（SOD）活性稍有波动,而3种多胺－腐胺（Put)精胺（Spd)和尸胺（Spn)在照射7天后均有积累,但在处理后期（21d)有所回落,推测由LOX主导的酶促膜过氧化作用和氧自由基引起的非酶促过作用在膜结构的破坏中起重要作用,SOD活性和多胺含量的变化蚕豆对UV－B胁迫的一种适应性生理反应。     

Regulation of exogenous spermidine on the reactive oxygen species level and polyamine metabolism in <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> (Mart.) Griseb under copper stress

Effects of exogenous spermidine (Spd) on the reactive oxygen species level and polyamine metabolism against copper (Cu) stress in Alternanthera philoxeroides (Mart.) Griseb leaves were investigated. Cu treatment induced a marked accumulation of Cu and enhanced contents of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and the generation rate of O₂ ^·−. It also significantly increased putrescine (Put) levels but lowered spermidine (Spd) and spermine (Spm) levels. The activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and polyamine oxidase (PAO) were all elevated with the increase of Cu concentration. However, application of exogenous Spd effectively decreased H₂O₂ content and the generation rate of O₂ ^·−, prevented Cu-induced lipid peroxidation and reduced Cu accumulation. Moreover, it declined level of endogenous Put and increased levels of Spd and Spm. Activities of ADC, ODC and PAO were all inhibited by exogenous Spd. The results indicated that application of exogenous Spd could enhance the tolerance of A. philoxeroides to Cu stress by reducing the reactive oxygen level and balancing polyamine metabolism.     

Effects of Exogenous Spermidine on Antioxidant System Responses of Typha latifolia L. Under Cd2+ Stress

The effects of foliar spraying with spermidine (Spd), ranging in concentration from 0.25 to 0.50mmol/L, on the antioxidant system under Cd2 stress (range 0.1- 0.2 mmol/L Cd2 ) in Typha latifolia L.grown hydroponically were investigated in order to offer a referenced evidence for an understanding of the mechanism by which polyamines (PAs) relieve the damage to plants by heavy metal and improve the phytoremediation efficiency of heavy metal-contaminated water. The results showed that Cd2 stress inhydrogen peroxide (H2O2) and malondialdehyde (MDA) contents in both leaves and caudices. With theexception of superoxide dismutase (SOD) activity in the leaves, an increase in the activities of catalase (CAT), guaiacol peroxidase (GPX), and glutathione reductase (GR) was observed in both leaves and caudices,SOD activity was increased in caudices, and ascorbate peroxidase (APX) activity was increased in leaves following Cd2 treatment. The reduced glutathione (GSH) content in both leaves and caudices and the reductive ascorbate content in leaves was obviously increased, which were prompted by the application of exogenous Spd. Spraying with Spd increased the activity of GR and APX in both leaves and caudices,whereas the activity of SOD, CAT, and GPX was increased only in caudices following spraying with Spd.with Spd. The decrease in MDA was more obvious following the application of 0.25 than 0.50 mmol/L Spd.It is supposed that exogenous Spd elevated the tolerance of T. latifolia under Cd2 stress primarily by increasing GR activity and the GSH level.     

外源Spd对高温胁迫下黄瓜幼苗叶片膜脂过氧化及质子泵活性的影响

以较为耐热的黄瓜品种‘津春4号’为试材,在人工气候箱中,采用石英砂培养加营养液浇灌的栽培方式,研究了叶面喷施外源亚精胺(Spd)对高温胁迫下黄瓜幼苗叶片膜脂过氧化程度、质子泵活性及其基因表达的影响.结果表明:高温胁迫下,外源Spd促进黄瓜幼苗株高、茎粗、干、鲜质量和叶面积显著增加,有效抑制叶片相对电导率、丙二醛(MDA)含量和脂氧合酶(LOX)活性的升高,有助于提高叶片细胞质膜和液泡膜H+ -ATPase活性,但在基因表达水平上无显著差异.外源Spd可显著降低黄瓜幼苗叶片膜脂过氧化程度,提高质子泵活性,从而稳定膜的结构和功能,缓解高温胁迫对黄瓜幼苗造成的伤害,提高幼苗对高温胁迫的耐性.     

外源多胺对铜胁迫下水鳖叶片多胺代谢、抗氧化系统和矿质营养元素的影响

采用营养液水培的方法,研究了外源亚精胺(Spd)和精胺(Spm)对Cu胁迫下水鳖叶片3种形态多胺(PAs)、抗氧化系统及营养元素的影响。结果表明:(1)Cu胁迫使水鳖叶片腐胺(Put)急剧积累,Spd和Spm明显下降,从而使(Spd+Spm)/Put比值也随之下降。外源Spd和Spm显著或极显著逆转Cu诱导的PAs变化,抑制Put的积累,缓解Spd和Spm的下降,从而提高了(Spd+Spm)/Put比值。(2)外源Spd和Spm抑制了Cu胁迫诱导的多胺氧化酶(PAO)的增加,缓解了二胺氧化酶(DAO)的下降。(3)与单一Cu胁迫相比,Spd和Spm显著或极显著提高了超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性和抗坏血酸(AsA)、谷胱甘肽(GSH)、游离脯氨酸(Pro)含量,从而降低了超氧阴离子(O2.-)产生速率和过氧化氢(H2O2)含量,极显著降低了丙二醛(MDA)含量,缓解了Cu诱导的氧化胁迫。(4)外源Spd和Spm显著或极显著缓解了Cu胁迫下矿质营养元素吸收平衡的紊乱。以上结果均说明了外施Spd和Spm可增加水鳖对Cu胁迫的耐受性。     

Enhanced susceptibility of photosynthesis to low-temperature photoinhibition due to interruption of chill-induced increase of S-adenosylmethionine decarboxylase activity in leaves of spinach (Spinacia oleracea L.)

The possible involvement of polyamines in the chilling tolerance of spinach (Spinacia oleracea L.) was investigated focusing on photosynthesis. During chilling at 8/5C (day/night) for 6 d, S-adenosylmethionine decarboxylase (SAMDC) activity increased significantly in leaves in parallel with the increase in putrescine and spermidine (Spd) content in leaves and chloroplasts. Treatment of leaves with methylglyoxal-bis(guanylhydrazone) (MGBG), an SAMDC inhibitor, resulted in the deterioration of plant growth and photosynthesis under chilling conditions, which was reversed by the concomitant treatment with Spd through the roots. Plants treated with MGBG showed lower photochemical efficiency of PSII than either the control or plants treated with MGBG plus Spd during chilling and even after transfer to warm conditions, suggesting an increase of photoinhibition due to low Spd in chloroplasts. Indeed, MGBG-treated plants had much lower activities of thylakoid electron transport and enzymes in carbon metabolism as well as higher degrees of lipid peroxidation of thylakoid membranes compared to the control. These results indicate that the enhanced activity of SAMDC with a consequential rise of Spd in chloroplasts is crucial for the cold acclimation of the photosynthetic apparatus in spinach leaves.     

Lipoxygenase activity and proline accumulation in leaves and roots of olive trees in response to drought stress

The olive tree ( Olea europaea L.) is commonly grown in the Mediterranean basin and is able to resist severe and prolonged drought. Levels of proline (PRO) and malondialdehyde (MDA), and the lipoxygenase (LOX) activity were determined in 2-year-old olive plants (cv. 'Coratina') grown in environmental conditions characterized by high temperatures and high photosynthetic photon flux density levels and gradually subjected to a controlled water deficit for 20 days. Before and during the experimental period, leaf and root samples were collected and analysed for PRO and MDA. The levels of PRO increased in parallel with the severity of drought stress in both leaves and roots. Significant increases of LOX activity and MDA content were also observed during the progressive increment of drought stress in both leaf and root tissues. Measurements of transpiration and photosynthetic rate, stomatal conductance and substomatal CO₂ concentration were carried out during the experiment. The accumulation of PRO indicates a possible role of PRO in drought tolerance. The increases of MDA content and LOX activity show that the water deficit is associated with lipid peroxidation mechanisms.     

Effects of Exogenous Spermidine on Antioxidant System Responses of Typha latifolia L. Under Cd^2＋ Stress

The effects of foliar spraying with spermidine (Spd), ranging in concentration from 0.25 to 0.50 mmol/L, on the antioxidant system under Cd^2 stress (range 0.1- 0.2 mmol/L Cd^2 ) in Typha latifolia L. grown hydroponically were investigated in order to offer a referenced evidence for an understanding of the mechanism by which polyamines (PAs) relieve the damage to plants by heavy metal and improve the phytoremediation efficiency of heavy metal-contaminated water. The results showed that Cd^2 stress induced oxidative injury, as evidenced by an increase in the generation of superoxide anion (O2), as well as the hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents in both leaves and caudices. With the exception of superoxide dismutase (SOD) activity in the leaves, an increase in the activities of catalase (CAT), guaiacol peroxidase (GPX), and glutathione reductase (GR) was observed in both leaves and caudices, SOD activity was increased in caudices, and ascorbate peroxidase (APX) activity was increased in leaves following Cd^2 treatment. The reduced glutathione (GSH) content in both leaves and caudices and the reductive ascorbate content in leaves was obviously increased, which were prompted by the application of exogenous Spd. Spraying with Spd increased the activity of GR and APX in both leaves and caudices, whereas the activity of SOD, CAT, and GPX was increased only in caudices following spraying with Spd. The generation of O2 and the H2O2 and MDA content in both leaves and caudices decreased after spraying with Spd. The decrease in MDA was more obvious following the application of 0.25 than 0.50 mmol/L Spd. It is supposed that exogenous Spd elevated the tolerance of T. latifolia under Cd^2 stress primarily by increasing GR activity and the GSH level.     

Arbuscular mycorrhizal influence on growth,photosynthetic pigments,osmotic adjustment and oxidative stress in tomato plants subjected to low temperature stress

The influence of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae, on characteristics of growth, photosynthetic pigments, osmotic adjustment, membrane lipid peroxidation and activity of antioxidant enzymes in leaves of tomato (Lycopersicon esculentum cv Zhongzha105) plants was studied in pot culture under low temperature stress. The tomato plants were placed in a sand and soil mixture at 25°C for 6 weeks, and then subjected to 8°C for 1 week. AM symbiosis decreased malondialdehyde (MDA) content in leaves. The contents of photosynthetic pigments, sugars and soluble protein in leaves were higher, but leaf proline content was lower in mycorrhizal than non-mycorrhizal plants. AM colonization increased the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in leaves. The results indicate that the AM fungus is capable of alleviating the damage caused by low temperature stress on tomato plants by reducing membrane lipid peroxidation and increasing the photosynthetic pigments, accumulation of osmotic adjustment compounds, and antioxidant enzyme activity. Consequently, arbuscular mycorrhiza formation highly enhanced the cold tolerance of tomato plant, which increased host biomass and promoted plant growth.     

Exogenous spermidine enhances Hydrocharis dubia cadmium tolerance

The effects of exogenous spermidine (Spd) on arginine decarboxylase (ADC), ornithine decarboxylase (ODC), polyamine oxidase (PAO), and diamine oxidase (DAO) activities, the rate of superoxide radical (O ₂ ^·? ) generation and polyamine (PA), malondialdehyde (MDA), and H₂O₂ contents in Hydrocharis dubia (Bl.) Backer leaves under cadmium (Cd) toxicity were studied after 6-day treatment. Cd stress increased putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels. In addition, the activities of ADC, DAO, and PAO were increased, while that of ODC was decreased. Exogenous application of Spd markedly reversed these Cd-induced effects. It also significantly reduced the generation of O ₂ ^·? and H₂O₂ and prevented lipid peroxidation. These results suggest that exogenous Spd can enhance the tolerance of H. dubia to Cd. The maintenance of PA homeostasis was necessary for plant metal tolerance.     

Antisense inhibition of a spermidine synthase gene highlights the role of polyamines for stress alleviation in pear shoots subjected to salinity and cadmium

Three transgenic European pear (Pyrus communis L.) lines with reduced spermidine synthase (SPDS) expression and spermidine (Spd) titers were developed using a construct containing an apple SPDS gene (MdSPDS1) in antisense orientation. After exposure to either salt or cadmium stress, growth inhibition was more severe in the antisense lines than in the wild-type (WT). The antioxidant system, as shown by glutathione (GSH) content, activity of glutathione reductase (GR) and superoxide dismutase (SOD), and proline accumulation, was not effectively induced under stress in the antisense lines as compared with the WT. The reduction in antioxidant system function in the antisense lines was accompanied by a greater accumulation of malondialdehyde (MDA), an indicator of lipid peroxidation. Growth inhibition, Spd level, and parameters indicative of the antioxidant system were significantly ameliorated by exogenous Spd application. Under either salt or cadmium stress, GSH content, GR and SOD activity, and proline accumulation were positively correlated with Spd, putrescine (Put), and total polyamine titers. Conversely, MDA level showed a significantly negative correlation with these polyamines under both stress conditions. Thus, the responses to stress treatments were first identified in the SPDS antisense European pears, and the results provide further evidence for the important role of polyamines in both salt and cadmium stress tolerance, in which the polyamines act, at least in part, by influencing the antioxidant system.     

Exogenous polyamines enhance copper tolerance of Nymphoides peltatum

The protective effects of polyamines (PAs) against copper (Cu) toxicity were investigated in the leaves of Nymphoides peltatum. Cu treatment increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby reducing the (Spd+Spm)/Put ratio in leaves. Exogenous application of Spd or Spm markedly reversed these Cu-induced effects for all three PAs and partially restored the (Spd+Spm)/Put ratio in leaves. It also significantly enhanced the level of proline, retarded the loss of soluble protein, decreased the rate of O2*- generation and H2O2 content, and prevented Cu-induced lipid peroxidation. Furthermore, exogenous Spd and Spm reduced the accumulation of Cu and effectively maintained the balance of nutrient elements in plant leaves under Cu stress. These results suggest that exogenous application of Spd or Spm can enhance the tolerance of N. peltatum to Cu by increasing the levels of endogenous Spd and Spm as well as the (Spd+Spm)/Put ratio.     

Spermidine alleviates the growth of saline-stressed ginseng seedlings through antioxidative defense system

Protective effects of exogenous spermidine (Spd), activity of antioxygenic enzymes, and levels of free radicals in a well-known medicinal plant, Panax ginseng was examined. Seedlings grown in salinized nutrient solution (150 mM NaCl) for 7 d exhibited reduced relative water content, plant growth, increased free radicals, and showing elevated lipid peroxidation. Application of Spd (0.01, 0.1, and 1 mM) to the salinized nutrient solution showed increased plant growth by preventing chlorophyll degradation and increasing PA levels, as well as antioxidant enzymes such as CAT, APX, and GPX activity in the seedlings of ginseng. During salinity stress, Spd was effective for lowering the accumulation of putrescine (Put), with a significant increase in the spermidine (Spd) and spermine (Spm) levels in the ginseng seedlings. A decline in the Put level ran parallel to the higher accumulation of proline (Pro), and exogenous Spd also resulted in the alleviation of Pro content under salinity. Hydrogen peroxide (H₂O₂) and superoxide (O₂⁻) production rates were also reduced in stressed plants after Spd treatment. Furthermore, the combined effect of Spd and salt led to a significant increase in diamine oxidase (DAO), and subsequent decline in polyamine oxidase (PAO). These positive effects were observed in 0.1 and 1 mM Spd concentrations, but a lower concentration (0.01 mM) had a very limited effect. In summary, application of exogenous Spd could enhance salt tolerance of P. ginseng by enhancing the activities of enzyme scavenging system, which influence the intensity of oxidative stress.     

Response of sun- and shade-adapted plants of Haberlea rhodopensis to desiccation

The differences in some morphological and physiological characteristics of sun- and shade-adapted Haberlea rhodopensis plants were compared. Changes in the photosynthetic activity, electrolyte leakage from leaf tissues, malondialdehyde content (MDA) and leaf anatomy were studied at different degrees of desiccation as well as after rehydration of plants. The MDA content in well-watered sun Haberlea plants was higher compared to shade plants suggesting higher lipid peroxidation, which is commonly regarded as an indicator of oxidative stress, but desiccation of plants at high light did not cause additional oxidative damage as judged by the unaffected MDA content. The electrolyte leakage from dried leaves (8% RWC) from both shade and sun plants increased fourfold indicating similar membrane damage. However, the recovery after rehydration showed that this damage was reversible. Well-watered sun plants had higher photosynthetic activity probably due to the larger thickness of the mesophyll layer in such plants. On the other hand, desiccation at high light reduced CO₂ assimilation which was in accordance with the stronger reduction of stomatal conductance. Stomata were visible only on the abaxial side of sun leaves having also higher abundance of non-glandular trichomes. Increased trichomes density and epicuticular waxes and filaments upon desiccation could help plants to increase reflection, reduce net radiation income, slow down the rate of water loss and survive adverse conditions.     

Silicon-mediated changes on some physiological and enzymatic parameters symptomatic of oxidative stress in barley grown in sodic-B toxic soil

The effect of silicon (Si) on the growth, sodium (Na), chloride (Cl), boron (B) concentrations, lipid peroxidation (MDA), membrane permeability (MP), lypoxygenase activity (LOX), proline (PRO) and H(2)O(2) accumulation, and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of barley grown in original sodic-B toxic soil were investigated. Si applied to the sodic-B toxic soil at 70, 140 and 280 mg kg(-1) levels significantly increased Si concentrations of the plants and counteracted the deleterious effects of sodicity (Na ions) and B on shoot growth. Membrane permeability and the concentrations of H(2)O(2) and MDA increased, while PRO concentration decreased in plants grown in sodic-B toxic soil without Si. LOX activity was increased by applied Si. Compared with control plants, the activities of SOD and CAT were decreased, but APX was increased by applied Si levels.     

干旱胁迫下亚精胺对玉米幼苗抗旱性影响的生理生化机制

为探究外源亚精胺(Spd)在增强玉米干旱胁迫耐受性中的作用,以‘先玉335’(干旱不敏感型)和‘丰禾1’(干旱敏感型)为试验材料,采用营养液水培法,研究了15%聚乙二醇(PEG-6000)模拟干旱胁迫下,外源Spd (0.1 mmol·L^-1)对玉米幼苗生长、光合特性、叶绿素含量、渗透调节物质、活性氧生成、膜质过氧化及根系活力的影响.结果表明:干旱胁迫下,外源Spd处理可显著促进干旱胁迫下玉米幼苗的生长;提高叶绿素含量、净光合速率(P_n)、气孔导度(g_s)、蒸腾速率(T_r)和水分利用效率(WUE),减缓‘丰禾1’叶片中胞间CO₂浓度(C_i)的升高,有效减轻干旱胁迫对玉米幼苗叶片光合作用的气孔限制和非气孔限制;增加脯氨酸和可溶性糖的含量;降低O₂^-·生成速率、H₂O₂和丙二醛(MDA)含量、细胞膜透性,有效缓解了胁迫对膜的伤害;增强幼苗根系活力;其中干旱敏感品种‘丰禾1’变化幅度大于耐旱品种‘先玉335’.表明在干旱胁迫下,外源Spd能促进玉米幼苗对光能的捕获与转换,增强光合作用,促进幼苗的生长,并能够通过减少玉米幼苗体内活性氧的产生,增加渗透调节物质的积累以稳定细胞膜系统,提高根系活力,从而增强幼苗对干旱逆境的适应性,且对干旱敏感品种‘丰禾1’的效果更显著.     

钙素和水分亏缺对黄瓜叶片细胞质膜透性的影响

用控制溶液的钙量[加或不加Ca(NO_3)_2]和渗透势(加聚乙二醇6000,202 g/L)的方法,研究了钙素和水分亏缺对黄瓜叶片细胞质膜透性的影响。结果表明:在渗透胁迫下,正常供钙的黄瓜叶片相对含水量(RWC)和膜透性变化较小、MDA增加不显著、SOD活性无明显改变;缺钙植株叶片的RWC随渗透胁迫处理线性下降,膜透性显著增大、MDA含量迅速提高、SOD活性也升高。在正常水分供应下,与供钙植株相比,缺钙植株SOD活性和MDA含量均较高,但RWC和膜透性无差异。在水分胁迫下,缺钙植株MDA和质膜透性与ΔRWC以及MDA与质膜透性之间均呈正相关。这些结果表明在水分胁迫下,缺钙处理叶片保水能力降低,使受害加重;同时,细胞质膜的稳定性降低。膜透性改变可能与在水分胁迫下体内的膜脂过氧化反应密切相关,即缺钙加速了膜脂过氧化反应,从而损害了质膜结构。     

光对小麦幼叶脂氧合酶活性及膜脂过氧化作用的影响

选用抗旱型小麦品种陕合６号和水分敏感型小麦品种郑引１号的黄化幼苗为材料,研究了光处理对小麦幼叶脂氧合酶活性和膜脂氧化作用的影响。结果表明：光处理后黄叶变绿,叶片中的ＬＯＸ活性降低,丙二醛含量和叶绿素含量增加,膜透性升高,ＩＵＦＡ升高。ＬＯＸ活性与光抑制过程的恢复,光保护过程及膜脂过氧化作用有关。光诱导产生的膜脂过氧化作用是一种“准膜脂过氧化作用”。