Proline antioxidant role in the common ice plant subjected to salinity and paraquat treatment inducing oxidative stress

Leaves of 4-week-old (juvenile) and 9-week-old (adult) plants of the halophyte Mesembryanthemum crystallinum L. (the common ice plant), cultured under controlled conditions in the phytotron, were treated with paraquat (0.1 μM), which produces superoxide radical, and (or) paraquat combined with introduction of NaCl (100 mM) or proline (5 mM) into nutrient medium. After a 20-h dark period (23°C), plants were transferred into light (4 h at 54.1 W/m² of photosynthetically active radiation) for stimulation of O°₂⁻ formation in plastids. Activities of antioxidant enzymes, the contents of MDA, H₂O₂, chlorophyll, and free proline were measured in leaves. Plant responses in two age groups, which differed in the type of photosynthesis (juvenile plants had C₃ type of photosynthesis, whereas adult plants were at the transition stage to Crassulacean Acid Metabolism (CAM) photosynthesis), differed in the levels of constitutive proline and proline, induced by NaCl and paraquat, as well as in activities of superoxide dismutase (SOD) and catalase. Changes in SOD activity and proline accumulation in response to paraquat treatment combined with NaCl revealed opposite dependence to accumulation of proline: the more proline accumulated in leaves, the lower activity of the enzyme. In response to paraquat treatment, the content of chlorophylls a and b most drastically declined in juvenile plants. Negative effect of salinity on the content of chlorophylls was lower than that of paraquat and was almost the same in plants of both age groups. Protective effect of exogenous proline was most profound in the case of paraquat treatment. Exogenous proline decreased the rate of lipid peroxidation, the content of superoxide radical and, consequently, SOD activity (almost fivefold), and increased the content of chlorophylls (a and b) in leaves of adult plants. The obtained data suggest that stress-induced accumulation of proline in the common ice plant has both osmoprotectory and antioxidant functions.     

The effect of zinc stress combined with high irradiance stress on membrane damage and antioxidative response in bean seedlings

Zinc (Zn) is a necessary element for plants, but excess Zn can be detrimental. The effect of Zn and high irradiance (HI) stress on the growth, lipid peroxidation (MDA), membrane permeability (EC), hydrogen peroxide (H₂O₂) accumulation, non-enzymatic antioxidants like proline accumulation and ascorbic acid (AsA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POX; polyphenol oxidase, PPO) of bean leaves were investigated under controlled growth conditions. The root length was not reduced at excess Zn level. Application of Zn significantly increased Zn concentration in the leaves of bean plants. Under Zn and HI stress, the Zn-deficient and Zn-excess conditions significantly increased the EC, MDA and H₂O₂ content of excised leaves of bean. The SOD activity was found to be increased significantly in both Zn-deficiency and Zn-excess leaves under Zn and HI stress. Under both Zn and HI stress conditions, the antioxidant enzyme activities; POX, PPO and the non-enzymatic antioxidants, AsA and proline accumulation were found to be significantly increased in the Zn-excess leaves which showed that the bean plant had the ability to tolerate the excess level of Zn and HI stress. A significant increase in MDA, H₂O₂, and EC with a simultaneous decrease in the antioxidant enzyme activities under Zn-deficiency compared to Zn-sufficient condition shows the inefficiency of the bean plant in response to Zn deficiency. To the best of our knowledge, this is the first report on the effect of Zn stress combined with HI stress in bean plant.     

Growth and triterpenic acid accumulation of Cyclocarya paliurus cell suspension cultures

Cyclocarya paliurus is a unique plant growing in central China with hypoglycaemic and hypolipaemia effects. To make better use of this functional food resource, cell suspension cultures and triterpenic acid accumulation were studied. Stable and uniform cell suspension cultures were established in liquid basal Murashige and Skoog medium supplemented with 2,4-dichlorophenoxy acetic acid (0.5 mg/L), naphthalene acetic acid (0.3 mg/L) and cytokinin (1.0 mg/L). According to the growth curve and triterpenic acid accumulation curve, the 8 ～ 10^th day postinoculation was the optimum time for subculture, and the 14^th day was the optimum time for harvest. Murashige and Skoog medium and woody plant medium were suitable for both cell growth and triterpenic acid accumulation. 3% sucrose (w/v), 60 mM total nitrogen (NO₃ ^?/NH₄ ⁺ = 2/1), 1.25 mM KH₂PO₄, 2 mM CaCl₂, and 2 mM MgSO₄ were all found to be fit for cell growth and triterpenic acid accumulation in a cell suspension culture of Cyclocarya paliurus. Total triterpenic acid, ursolic acid and oleanolic acid content in suspended cultured cells were all significantly higher than that of leaves and calluses (P ? 0.01), with levels up to 6.24, 2.28, and 0.94% (of dry weight), respectively. The betulinic acid content of suspended cultured cells also reached 0.82%, which was significantly higher than that of calluses. These results suggest that suspended cultured cells of Cyclocarya paliurus were rich in triterpenic acids and could be used for the production of total triterpenic acid, ursolic acid, oleanolic acid and betulinic acid.     

AM真菌对盐胁迫下番茄幼苗生理特征及AVP1表达的影响

采用温室盆栽试验研究不同NaCl浓度（0、50 和85 mmol/L）持续胁迫接种摩西球囊霉和地表球囊霉 2种AM真菌对加工番茄耐盐性的影响。结果显示:（1）在0 mmol/L NaCl处理条件下,2种菌的番茄菌根化苗的根系活力、叶片中可溶性糖、可溶性蛋白、根系脯氨酸含量以及超氧化物歧化酶和过氧化物酶活性均高于非菌根植株,且丙二醛含量低于非菌根植株,但差异不显著。（2）在50、85 mmol/L NaCl浓度胁迫下,接种2种菌根真菌可显著提高番茄植株根系活力,促进叶片中可溶性糖、可溶性蛋白及根系脯氨酸含量的积累,显著提高叶片中与抗逆相关的超氧化物歧化酶和过氧化物酶的活性,减少丙二醛在根系中的积累;随着NaCl浓度的增加,效果更为明显。（3）RT-PCR分析显示,AM真菌和盐胁迫共同调控H⁺转运无机焦磷酸酶H⁺- PPase的表达,随NaCl浓度的增加,AVP1基因表达量下降,但菌根化番茄植株的AVP1基因表达量显著高于非菌根植株。研究表明,接种AM真菌后,菌根化植株可通过显著促进幼苗体内渗透调节物质积累和抗氧化酶活性的提高,有效降低体内膜脂过氧化水平,同时过量表达AVP1基因增加了番茄植株中离子向液泡膜的转运,从而缓解盐胁迫对植株的伤害,增强番茄幼苗对盐胁迫的耐性。     

Cadmium effects on mineral nutrition and stress in <Emphasis Type="Italic">Potamogeton crispus</Emphasis>

The mechanisms of plant tolerance to cadmium stress were studied by short-term exposure of Potamogeton crispus L. to various concentrations of Cd ranging from 0 to 0.09 mM. The accumulation of Cd and its influence on nutrient elements, chlorophyll pigments, ultrastructure, proline and MDA contents, and free radical production, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) were investigated. The higher Cd concentration in the medium resulted in a significant enhancement of Cd accumulation. Photosynthetic pigment content decreased and ultrastructural damage to the leaf cells was aggravated with the increase in the Cd concentrations. Disruption of chloroplasts and mitochondria was observed even at the lowest concentration of Cd. Meantime, the rate of O₂^*− generation and the contents of H₂O₂ and MDA significantly increased under Cd stress, suggesting that Cd caused oxidative stress. In addition, the antioxidant system was clearly activated following Cd exposure. SOD and POD activities increased initially and then decreased, while APX and GR activities markedly increased. Simultaneously, mineral nutrition was disturbed. While K, P, Ca, and Cu contents decreased, Na, Fe, and Mn contents increased. Induction of antioxidant enzyme activities in leaves exposed to elevated Cd concentrations may be involved in Cd tolerance of P. crispus.     

Salinity attenuates nickel-accumulating capacity of <Emphasis Type="Italic">Atropa belladonna</Emphasis> L. plants

Comparative analysis of growth and composition of Atropa belladonna L. plants was performed after separate and combined additions of NaCl and NiCl₂ to the nutrient medium. Plants were grown in water culture on modified Johnson solution for 8 weeks until the formation of the fifth leaf pair. Thereafter, NiCl₂ was introduced at final concentrations of 100 and 150 μM into the medium either separately or in combination with 100 mM NaCl. After completing the 7-day treatment with Ni ions, the plants' weight and the content of water and photosynthetic pigments were determined. The content of Ni, free polyamines (putrescine, spermidine, spermine), and atropine was determined in plant roots and leaves, whereas the content of Fe, proline, and malondialdehyde (MDA) was examined in leaves only. The distribution of Ni in various tissues was inspected using the dimethylglyoxime method. The presence of NiCl₂ in growth media diminished the increments in fresh weight of shoots and roots; lowered the content of water, pigments, and iron in leaves; and initiated chlorosis. The leaves of Ni-treated plants accumulated larger amounts of atropine, putrescine, proline, and MDA with respect to the control levels of these compounds. In contrast to the action of Ni alone, the combined application of NaCl and NiCl₂ was followed by the increased content of water and pigments in leaves. The presence of NaCl in the medium restricted the entry of Ni into roots and diminished the levels of MDA and proline in leaves. After growing the plants in the presence of 100 and 150 μM NiCl₂, nickel was located in the root outer cortex and the rhizoderm. In plants treated with 150 μM NiCl₂, nickel was also observed in tissues of the central cylinder, mostly in the pericycle, phloem, and xylem. In plants grown in the presence of 150 μM NiCl₂ and 100 mM NaCl, the decreased accumulation of nickel was noted in the tissues of the central cylinder in the root hair zone. Thus, the combined action of Ni and moderate salinity reduced nickel accumulation in roots and aboveground organs of A. belladonna plants. The reduced Ni content in plants mitigated the toxic effect of Ni present in the medium. This was manifested in stabilization of leaf water status, an increase in the content of photosynthetic pigments, and alleviation of oxidative stress, which was assessed from the content of low-molecular organic compounds exhibiting stress-protective and antioxidant action (proline, MDA, free polyamines, and atropine).     

An efficient in vitro plantlet regeneration of <Emphasis Type="Italic">Cryptocoryne wendtii</Emphasis> and <Emphasis Type="Italic">Cryptocoryne becketti</Emphasis> through shoot tip culture

An efficient micropropagation protocol was established for Cryptocoryne wendtii and Cryptocoryne becketti using shoot tips explants. Multiple shoots were induced from shoot tip explants of both species cultured on agar-gelled as well as liquid MS medium supplemented with 0.5 mg/L BA and 0.2 mg/L IBA (proliferation medium). The multiple shoots of both the species formed on agar-gelled as well as liquid medium were vigorously growing with well-developed roots and leaves after 4 weeks of culture. Highest number of multiple shoots was obtained from shoot tip explants of both the species cultured in liquid proliferation medium after 4 weeks of culture. The shoot tip explants of C. wendtii and C. becketti, that were cultured in liquid proliferation medium (2 weeks) followed by culturing on agar-gelled proliferation medium (2 weeks) also produced the multiple shoots. Shoot tips cultured on agar-gelled medium produced the least number of multiple shoots after 4 weeks of culture. Histological study did not show any abnormalities in the leaves of in vitro plantlets of both the species, cultured in agar-gelled and liquid proliferation medium. The leaves of the in vitro plantlets formed normal mesophyll cells and vascular bundles. More than 95% of the acclimatized plantlets grew vigorously without any morphological abnormalities.     

Mechanical stimulation-induced chilling tolerance in tobacco suspension cultured cells and its relation to proline

Mechanical stimulation (MS), widely existing but usually ignored in nature, is one of the major environmental stress factors. MS by increasing the rotational speed of shaker incubator could alleviate a decrease in vitality of tobacco (Nicotiana tabacum L.) suspension cultured cells and reduce the accumulation of MDA under chilling stress at 1°C, which in turn improved survival percentage under chilling stress and regrowth ability of tobacco suspension cells after chilling stress. In addition, MS could increase the activity of Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and induce the accumulation of endogenous proline in tobacco cells; exogenously applied proline also could enhance its endogenous level under normal culture conditions and survival percent-age of the cells under chilling stress. These results suggest that MS could improve chilling tolerance of tobacco suspension cells and the acquisition of this chilling tolerance was related to proline.     

海滨滨麦叶片和根对不同厚度沙埋的生理响应差异分析

以烟台海岸抗风沙植物滨麦为研究材料,通过对不同厚度沙埋下其叶片和根部抗氧化酶活力(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))、丙二醛(MDA)含量和渗透调节物含量变化的分析,探讨了叶片和根部对沙埋生理响应的差异。试验按滨麦成株株高(约40 cm)对其进行了轻度沙埋(在株高1/4处)、中度沙埋(2/4处)和重度沙埋(3/4处)。在沙埋第6天,分别测定了不同厚度沙埋处理下,植株各段叶片和根抗氧化酶活力、MDA和渗透调节物含量。结果表明,轻度和中度沙埋均加速植株生长。与对照相比,经轻度、中度沙埋处理6 d,叶片平均MDA含量增加,在重度沙埋下降低。不同厚度沙埋6 d,叶片平均SOD活力和脯氨酸含量增加,而CAT活力、可溶性糖和可溶性蛋白质含量下降。但不同厚度沙埋均使沙上叶片MDA、脯氨酸、可溶性蛋白质含量和SOD和CAT活力增加,尤其是叶片顶部增加最为明显,使沙下叶片MDA、可溶性糖、可溶性蛋白质含量和CAT活力下降,导致同株沙上和沙下叶片MDA、脯氨酸、可溶性糖、可溶性蛋白质含量和SOD和CAT活力差异显著(P0.05)。与叶片相比,根中MDA、可溶性蛋白质含量和SOD和CAT活力较低,而POD活力和可溶性糖含量较高并与叶片差异显著(P0.05)。不同厚度沙埋6 d,滨麦根中MDA和可溶性蛋白质含量变化较小,可溶性糖含量和CAT、POD、SOD活力略有降低。研究表明,滨麦根和叶片对不同厚度沙埋的生理响应不同。沙埋直接作用于叶片并诱发叶内氧自由基积累,但叶片通过快速激活的抗氧化酶保护系统(CAT、SOD)维持氧自由基代谢平衡,以及渗透调节物(脯氨酸、可溶性糖)的积累维护细胞水分代谢平衡,并满足能量的需求和快速生长。但在不同厚度沙埋下,由于根系不受沙埋直接影响而生理变化较小,并且还维持较低的膜脂过氧化水平,这可能是根能维持正常的吸水输水功能并在沙埋处理过程中和沙埋后地上叶片快速生长摆脱沙埋的重要物质基础。     

Elicitation of diacetylenic compounds in suspension cultured cells of eggplant

Induction of stress metabolites in the suspension cultured cells of eggplant (Solanum melongena L.) was examined. When autoclaved RNase A or nigeran, both of which are nonspecific phytoalexin elicitors in bean cells, were added to the cell culture of eggplant, greatly enhanced levels of three compounds were observed. One of them was cis-pentadeca-6-ene-1,3-diyne-5,15-diol, a novel diacetylenic compound. This compound has considerable fungitoxic activity. Also identified was falcarindiol, another fungitoxic diacetylenic compound previously reported as one of the phytoalexins in infected tomato fruits and leaves. Elicited compounds preferentially accumulated in the culture medium rather than in the cells and decreased to original levels during prolonged culturing. The elicitation of these compounds was closely correlated with cellular damage in terms of the decrease of growth rate and was inhibited by 10 micromolar cycloheximide.     

Protective effects of complementary Ca2+ on low-light-induced oxidative damage in tall fescue

Low-light (LL) intensity is a primary abiotic stressor that negatively influences turf grass quality. In the present experiment, we studied the effect of exogenous Ca²⁺ (0, 10, 50, 100, and 200 mM) on the antioxidant system, the accumulation of MDA and proline, the content of photosynthetic pigments in plant leaves in order to investigate whether exogenous Ca²⁺ treatment improves LL tolerance in tall fescue (Festuca arundinacea Schreb.). We have found that LL significantly reduced a number of growth parameters (plant height, leaf width, leaf fresh weight, root fresh weight, leaf dry weight, and root dry weight), chlorophyll (Chl) a and Chl b contents, and carotenoid (Car) levels, while considerably enhancing electrolyte leakage (EL), MDA accumulation, calcium (Ca²⁺) concentration, and generation of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂) and superoxide radical (O ₂ ^·? ). Moreover, LL significantly induced the activities of antioxidant enzymes, such as peroxidase (POD) and catalase (CAT), and slightly increased the activity of superoxide dismutase (SOD) in tall fescue leaves. In contrast, POD and SOD activities declined considerably while CAT activity significantly increased in plant roots under LL stress. The application of 50 mM Ca²⁺ significantly improved the aforementioned growth parameters, the content of photosynthetic pigments, and further enhanced the activities of POD, SOD, and CAT, but decreased electrolyte leakage and MDA and H₂O₂ levels in the leaves and roots of tall fescue under LL stress. These results suggest that Ca²⁺ is likely involved in a resistance to LL by regulating antioxidant enzyme action in tall fescue leaves and roots.     

Effect of low above-zero temperature on the content of low-molecular antioxidants and activities of antioxidant enzymes in green barley leaves

We studied the effect of low above-zero temperature (2°C) on the content of low-molecular antioxidants (ascorbic acid, glutathione, and carotenoids) and also activities of antioxidant enzymes (ascorbate peroxidase, APO; catalase, CAT; glutathione reductase, GR; and superoxide dismutase, SOD) in green barley (Hordeum vulgare L.) seedlings. Under stress conditions, the content of low-molecular antioxidants, especially that of reduced ascorbate form, increased. Low-temperature stress activated APO, CAT, GR, and SOD. First enzymes responding to the action of stress factor were APO and CAT, i.e., enzymes neutralizing hydrogen peroxide in plant cells, which indicated H₂O₂ active generation at low temperature. Cytoplasmic SOD was more active than its chloroplast isoforms. This indicates that oxidative process initiation under low-temperature stress occurred more active in the cytosol. After termination of stress-factor action, the content of total ascorbate, glutathione, and carotenoids reduced rapidly to the level close to the initial one. During post-stress period, the amount of reduced ascorbate declined as well; however, it remained at the level higher than the initial one. Activities of APO and CAT dropped sharply; activities of GR and SOD reduced gradually. Thus, reduced ascorbate, APO, and CAT play an important role in plant cell defense against above-zero temperatures close to zero; reduced ascorbate, GR, and SOD are especially important during post-stress period.     

铝胁迫对海莲幼苗保护酶系统及脯氨酸含量的影响

为探讨Al~(3+)胁迫对海莲的影响,研究了10～50 mmol/L Al~(3+)处理下海莲幼苗叶片和根系的过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)的活性以及可溶性蛋白质、丙二醛(MDA)和游离脯氨酸(Pro)含量的变化。结果表明,海莲幼苗能耐受50 mmol/L的Al~(3+)胁迫处理,具有较高的耐铝性。但在50 mmol/L Al~(3+)处理时,海莲幼苗叶片和根系的质膜系统膜脂过氧化加重,MDA含量增加;细胞活性氧代谢失衡。在保护酶系统中,Al~(3+)处理促进了叶片中APX和POD活性的提高,降低了CAT的活性,SOD的活性呈下降趋势;海莲根部POD和SOD活性均显著提高,而CAT活性下降。25～50 mmol/LAl~(3+)处理下,海莲叶片和根部可溶性蛋白质含量均显著下降;Pro的含量在叶片和根均有显著增加。     

Protoplast isolation,culture and regeneration from Egyptian cultures of Pea and Beans

Abstract

A protocol of protoplast isolation from Egyptian varieties of pea and bean is reported. Protoplast cultures were established from apical shoots of pea (Pisum sativum) and suspension cultures of bean (Phaseolus vulgaris). To isolate protoplasts of pea, apical shoot tissues were digested for 10 h using enzyme solution containing 1% pectinase, 0.5% cellulase, 0.5% hemicellulase, 10% mannitol and 0.1% CaCl₂-2H₂O. For protoplast isolation from suspension culture of bean, collected cells were incubated for 6 h in digestion solution containing 0.5% pectinase, 0.25% of each of cellulase and hemicellulase, 10% mannitol and 0.1% CaCl₂-2H₂O. Purified protoplasts were cultured in liquid culture medium. Microcalli were obtained after 30 days of culture. Calli colonies with a diameter of about 5 mm were developed after one month of culturing on solid B5 medium containing 2% sucrose, 2 g/l casein hydrolysate, 0.7% agar and supplemented with either 1 mg/l of each 2,4-D and kin in case of pea or 2 mg/l 2,4-D+0.5 mg/l kin in case of bean. Protoplast derived callus of pea was successfully differentiated into shoot and root, and highest frequency of shoot organogenesis was recorded on medium containing 0.5 mg/l NAA+2 mg/l BA. Protoplast derived callus of bean, on the other hand, gave rise to a high frequency of root formation when cultured on medium containing 1 mg/l NAA, but attempts to regenerate shoots from this callus was unsuccessfull.     

Effect of La(III) on the growth and aging of root of loquat plantlet in vitro

The effect of lanthanum on the adventitious root growth, activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), O₂ production rate, MDA content, and the relative plasma membrane permeability in roots of loquat test-tube plantlet were studied. Addition of lanthanum chloride (0.5 μmol/L) to the culture medium significantly increased the length of roots, increased the dry weight, enhanced the activities of SOD, CAT, and POD, decreased O₂ production rate, malondialdehyde (MDA) contents, and the relative plasma membrane permeability. The relatively stable membrane structure of cell could defer the root aging of the plantlet in vitro. There are important theory meaning and practical value in applying LaCl₃ in the rooting medium to raise the rate of rooting and transplant for wood plant.     

Interactive effects of salicylic acid and silicon on oxidative damage and antioxidant activity in spinach (<Emphasis Type="Italic">Spinacia oleracea</Emphasis> L. cv. Matador) grown under boron toxicity and salinity

We investigated individual and combined effects of salinity, soil boron (B), silicon (Si) and salicylic acid (SA) on the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) and non-enzymatic antioxidants (AA), proline, chlorophyll, anthocyanin, H₂O₂ concentration, stomatal resistance (SR), lipid peroxidation (MDA), membrane permeability (MP), and the uptake of sodium (Na), chloride (Cl), boron and Si of spinach plants. In general, salinity significantly increased H₂O₂ and proline concentrations, antioxidant activity, membrane permeability, lipid peroxidation and SR of the spinach plants, indicating that they were stressed, whereas application of B only increased proline concentration. However, plant fresh weights did not decline with either treatment. The application of Si decreased H₂O₂ and increased the activity of SOD and CAT. The application of SA increased SOD activity. Neither SA nor Si had any effect on the proline concentration, or MP. However, application of Si increased chlorophyll concentration and decreased lipid peroxidation (MDA concentration). Si treatment had no effect on SR. The concentration of B in the tissues, which was strongly increased by B treatment, was decreased by NaCl. As a result of salinity, concentrations of Na⁺ and Cl⁻ ions were increased in the plant tissues, and application of Si slightly increased these concentrations. These results indicate that exogenous Si application increases stress tolerance of spinach, a plant that is naturally reasonably resistant to combined salinity and B toxicity, by the enhancement of antioxidant mechanisms that reduce membrane damage. Exogenous SA has a less obvious effect, although the levels of salinity and boron stress applied were not sufficient in this experiment to reduce plant fresh weight.     

2个欧李品种对碳酸盐胁迫生理响应的初步研究

在盆栽条件下,以不同浓度的NaHCO₃溶液浇灌农大欧李3和4号2年生组培苗,测定苗木叶片的生理指标。结果表明：随胁迫时间的延长,两个品种的叶绿素a呈先变化平缓后降低趋势,各处理间差异显著;叶绿素a/b在整个处理时期变化平稳;脯氨酸呈先变化平缓后升高趋势;农大欧李3号的电解质外渗率、MDA和POD活性呈先变化平缓后升高再降低的趋势,各处理间差异不显著;中、低浓度SOD活性整个胁迫期变化平缓,高浓度的在整个胁迫期间变化较大,各处理间差异极其显著;农大欧李4号电解质外渗率、SOD、POD和MDA在处理期间呈先升高后降低趋势,胁迫解除后,高浓度处理的电解质外渗率、SOD、POD活性上升、低浓度处理下降,MDA则相反。在长期的NaHCO₃胁迫过程中,农大欧李3号和4号都显示了强的耐盐性。     

Exogenous proline alleviates the effects of H2O2-induced oxidative stress in wild almond species

The effect of proline on the antioxidant system in the leaves of eight species of wild almond (Prunus spp.) exposed to H₂O₂-mediated oxidative stress was studied. The levels of endogenous proline (Pro) and hydrogen peroxide, and the activities of total superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and guaiacol peroxidase (POD) were measured. The degradation of chlorophyll but not carotenoids occurred in leaves in the solution of 5 mM H₂O₂. An increase in membrane lipid peroxidation was observed in H₂O₂ treatment, as assessed by MDA level and percentage of membrane electrolyte leakage (EL). Significant increases in total SOD and CAT activities, as well as decreases in APX and POD activities, were detected in H₂O₂-treated leaves. The three SOD isoforms showed different behavior, as Mn-SOD activity was enhanced by H₂O₂, whereas Fe-SOD and Cu/Zn-SOD activities were inhibited. In addition, Pro accumulation up to 0.1 ??mol/g fr wt, accompanied by significant decreases in ascorbate and glutathione levels, was observed in H₂O₂-treated leaves. After two different treatments with 10 mM Pro + 5 mM H₂O₂, total SOD and CAT activities were similar to the levels in control plants, while POD and APX activities were higher if compared to the leaves exposed only to H₂O₂. Pro + H₂O₂ treatments also caused a strong reduction in the cellular H₂O₂ and MDA contents and EL. The results showed that Pro could have a key role in protecting against oxidative stress injury of wild almond species by decreasing membrane oxidative damage.     

Effect of salinity and waterlogging on growth,anatomical and antioxidative responses in <Emphasis Type="Italic">Mentha aquatica</Emphasis> L.

Salinity and waterlogging are two stresses which in nature often occur simultaneously. In this work, effects of combined waterlogging and salinity stresses are studied on the anatomical alteration, changes of enzymatic antioxidant system and lipid peroxidation in Mentha aquatica L. plants. Seedlings were cultured in half-strength Hoagland medium 50 days after sowing, and were treated under combination of three waterlogging levels (well drained, moderately drained and waterlogging) and NaCl (0, 50, 100, 150 mM) for 30 days. Moderately drained and waterlogging conditions induced differently aerenchyma formation in roots of M. aquatica salt-treated and untreated plants. Moreover, stele diameter and endodermis layer were also affected by salt stress and waterlogging. Salt stress significantly decreased growth, relative water content (RWC), protein level, catalase (CAT) and polyphenol oxidase (PPO) activities, and increased proline content, MDA content, H₂O₂ level and activities of superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX). Waterlogging in salt-untreated plants increased significantly growth parameters, RWC, protein content, antioxidant enzyme activity, and decreased proline content, H₂O₂ and MDA levels. In salt-treated plant, waterlogging caused strong induction of antioxidant enzymes activities especially at severe stress condition. These results suggest M. aquatica is a waterlogging tolerant plant due to significant increase of antioxidant activity, membrane stability and growth under water stress. High antioxidant capacity under waterlogging can be a protective strategy against oxidative damage, and help to salt stress alleviation.     

Scots pine as a model plant for studying the mechanisms of conifers adaptation to heavy metal action: 2. Functioning of antioxidant enzymes in pine seedlings under chronic zinc action

Functioning of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APO), and guaiacol peroxidases (GPO)) and low-molecular organic ROS scavengers (proline and phenolic compounds) in various organs (roots, cotyledons, stem, and needle) of 6-week-old seedlings of pine (Pinus sylvestris L.) developing in the chronic presence of ZnSO₄ (50, 100, and 150 μM). Pine seedlings were grown in water culture in the climate-controlled chamber at an irradiance of 37.6 W/m² with a 16-h photoperiod, an air temperature of 23 ± 1/15 ± 1°C (day/night), and a relative humidity of 55/70% (day/night). Endogenous Zn content was a key factor determining SOD activity decomposing superoxide into H₂O₂ and O₂. Hydrogen peroxide produced is efficiently destroyed by CAT and also by APO and GPO. At the same time, the content of proline increased (especially at 150 μM ZnSO₄), but the content of phenolic compounds remained unchanged. All these processes help to maintain stable intracellular levels of O₂^⊙− and H₂O₂ at elevated zinc concentrations and to prevent generation of hydroxyl radical and development of oxidative stress.