Lipid peroxidation and peroxide-scavenging enzymes associated with accelerated aging of peanut seed

Accelerated aging is known to reduce seed viability and vigor in many crop species. The phenomenon is due in part to aging-induced lipid peroxidation, which has the potential to damage membranes of the seed tissues. This study was undertaken to evaluate the effect of accelerated aging on germinability and several physiological characteristics related to peroxidation in the seed of two peanut cultivars. Accelerated aging was achieved by incubating seed at 45°C and 79% relative humidity in a closed chamber for 3, 6, or 9 days. The results indicate that accelerated aging inhibited seed germination and seedling growth. Enhanced lipid peroxidation and increased peroxide accumulation were observed in the axis and cotyledons of aged seed. Accelerated aging also inhibited the activity of superoxide dismutase, peroxidase, ascorbate peroxidase, and lipoxygenase. Seed axes appeared to be more susceptible to aging than cotyledons. The changes in germination and physiological activities, expressed as a function of aging duration, were similar in the two cultivars, despite differences in their seed weight.     

Changes in malondialdehyde content and in superoxide dismutase, catalase and glutathione reductase activities in sunflower seeds as related to deterioration during accelerated aging

Sunflower ( Helianthus annuus L.) seeds progressively lost their ability to germinate at 25°C, the optimal temperature for germination, after accelerated aging was carried out at 45°C (a temperature too high to permit germination) in water or at 76 or 100% relative humidity (RH). The deleterious effects of the high-temperature treatment increased with increasing seed moisture content. Incubation of seeds at 45°C in water resulted in electrolyte leakage, which indicated a loss of membrane integrity. A relationship between leakage and loss of seed viability could not be assumed, since no increase in electrolyte efflux occurred after aging al 100% RH. Accelerated aging induced accumulation of malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. However, there was no direct relationship between lipid peroxidation and deterioration in membrane integrity. Loss of seed viability was also associated with a decrease in superoxide dismutase, catalase and glutathione reductase activities. Finally, the results obtained suggest that sunflower seed deterioration during accelerated aging is closely related to a decrease in the activities of detoxifying enzymes and to lipid peroxidation.     

Lipid peroxidation and peroxide-scavenging enzymes associated with accelerated aging and hydration of watermelon seeds differing in ploidy

Hydration offers an effective means for raising seed performance in many crop species. The objective of this study was to evaluate the effect of vermiculite hydration on germinability and several physiological activities related to vigor in artificially aged watermelon seeds differing in ploidy. Aging was achieved by incubating the seeds at 45°C and 79% relative humidity for 6 days, then the seeds were air-dried to their original moisture level (4.7%). Hydration was achieved by mixing the untreated and aged seeds with moist vermiculite No. 3 at 25°C for 24 h. The partially hydrated seeds were air-dried at 25°C for 36 h to 4.7% moisture level. Significant differences existed between unaged and aged seeds, with lower germination percentage and slower germination speed in the latter. Aging also increased lipid peroxidation and reduced the activity of peroxide-scavenging enzymes. The germinability of aged watermelon seed was restored partially by vermiculite hydration. The activities of protein synthesis and peroxide-scavenging enzymes in axis and cotyledon portions of the seeds were also increased by hydration treatment. The changes in germination and related physiological responses in relation to aging and hydration are similar in seeds differing in ploidy, despite differences in their germination performance, seed leakage, extent of lipid peroxidation and activities of peroxide-scavenging enzymes.     

人工老化处理对结球甘蓝种子生理生化特性的影响

以结球甘蓝品种‘冬升’种子为材料,研究高温(40℃)高湿(相对湿度100%)人工老化处理过程中种子的萌发特性、种子浸出液相对电导率和丙二醛、可溶性蛋白、可溶性糖含量以及抗氧化酶活性的变化,以揭示种子劣变的机理。结果表明:(1)人工老化处理甘蓝种子的含水量和不正常苗率均随着老化时间的延长逐渐增加,而种子发芽势、发芽率、发芽指数和活力指数的增加均逐渐降低。(2)随着处理天数的延长,老化处理甘蓝种子的浸出液电导率显著增大,浸出液可溶性糖含量逐渐升高,可溶性蛋白含量表现出显著下降趋势,而种子MDA含量呈先升高后逐渐下降的趋势。(3)在结球甘蓝种子老化进程中,其种子中SOD、POD、CAT活性变化的趋势相似,均随老化程度的加深而逐渐降低;而APX活性在老化处理的最初2d显著增加,第6天显著降低。研究发现,在结球甘蓝种子老化进程中,种子活力和萌发率显著降低,其种子浸出液电导率、可溶性蛋白含量、可溶性糖含量、保护酶活性变化与种子老化及劣变程度密切相关,膜脂过氧化作用可能是引起或加剧种子老化劣变的重要原因之一。     

Biochemical changes induced by accelerated aging in sunflower seeds. I. Lipid peroxidation and membrane damage

When stored at 42°C and 100% relative humidity for 1 to 8 days, sunflower seeds (Helianthus annuus L. cv. Rodeo) aged prematurely and lost 25% of their initial viability. A ten-fold increase in conjugated dienes as well as a decrease of unsaturated fatty acids in diacylglycerol and polar lipids fractions were observed after 8 days of accelerated aging, demonstrating the occurrence of lipid peroxidation in prematurely aged sunflower seeds. However, the viability remained relatively high. The absence of membrane damage in seeds and of lipid peroxidation in isolated microsqmes suggested that lipid peroxidation concerned mainly lipid reserves. These results suggest that, at least within the first 8 days of treatment, the lipid reserve in sunflower seeds might act as a detoxifying trap, protecting membranes from excessive damage.     

The Maillard reaction and oxidative stress during aging of soybean seeds

The chemical reactions that may lead to the loss of seed viability were investigated both during the accelerated aging and natural aging of soybeans ( Glycine max Merrill cv. Chippewa 64). Under conditions of accelerated aging (36°C and 75% RH), fluorescence of soluble proteins accumulated, which was closely correlated with the loss of seed germinability and vigor. We were able to show this correlation by using partially purified proteins for the assay. Fluorescence also increased in seeds under good storage conditions (5°C for up to 21 years), although there was a less significant correlation between seed viability and the accumulation of fluorescent products during the time of natural aging. The rise in protein fluorescence is interpreted as an increase of Maillard products. The carbonyl content of soluble proteins (a measure of the oxidative damage) did not change significantly during either accelerated aging or natural aging: however the elimination of carbonyls during germination seemed to be hindered in seeds that had poor germination. The Maillard reaction may be a consequence of the formation of reducing sugars through a gradual hydrolysis of oligosaccharides during aging. Preliminary evidence from the natural aging study showed that, when seeds were in the glassy state, the sugar hydrolysis was inhibited. These results suggest that the Maillard reaction and oxidative reaction may play an important role in seed deterioration.     

Changes in oxidative stress enzymes during artificial ageing in cotton (Gossypium hirsutum L.) seeds

The present study was carried out to elucidate the mechanism of seed deterioration in two cotton (Gossypium hirsutum L.) cultivars (HS6 and H1098). The seeds were artificially aged at 40 +/- 1 degree C and 100% relative humidity for 4 days. In both cultivars, germinability decreased, whereas membrane deterioration, as assayed by electrical conductivity of the seed leachates, increased progressively with artificial ageing. The decrease in germinability was well correlated with increased accumulation of total peroxide and malondialdehyde content and decreased activities of antioxidant enzymes peroxidase, catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase. Hydropriming for 2 h and ascorbic acid priming for 12 h partially maintained germination and the activities of various antioxidant enzymes under artificial ageing and the accumulation of peroxide and MDA content was decreased. The results suggest that cotton seed deterioration during accelerated ageing is closely related to a decrease in activities of various peroxide scavenging enzymes and to lipid peroxidation.     

黄皮种子脱水敏感性与脂质过氧化作用

黄皮种子自然脱水时,种子的发芽率和发芽指数迅速下降;种子浸泡液的电导率和可溶性物质的量大大增加;线粒体膜和质膜ATPase的活性下降;种子中SOD活性先上升,然后下降;脂质过氧化产物MDA和脂质氢过氧化物的量大大增加。DDC、MDA和Fe2 促进脂质过氧化作用,降低种子生活力;ASA和甘露醇对脂质过氧化有抑制作用,提高种子生活力。     

Aging and Loss of Germination in Rye Seeds Is Accompanied by a Decreased Fragmentation of Nuclear DNA at Loop Domain Boundaries

To investigate the processes that occur in the embryo cell nuclei in the course of natural and accelerated aging of rye seeds, nuclear DNA structural organization into chromatin loop domains was studied. The loss of germination was shown to be accompanied by a decreased excision of chromatin loop domains. The study of chromatin accessibility to DNase I did not reveal any considerable changes in chromatin architecture that would explain the decreased DNA fragmentation at matrix attachment regions. A soluble nuclear protein of ca. 31 kD was found to manifest nuclease activity, which declined with the loss of germination. The study of DNA fragmentation in histone-depleted nuclei (nucleoids) disclosed a nuclease activity resistant to 2 M NaCl extraction and sensitive to the specific inhibitors of DNA topoisomerase II; the latter activity also declined with aging. The authors conclude that the changes in DNA fragmentation patterns in aging seeds were primarily caused by a decreased activity of the enzymes accounting for the excision of chromatin loop domains.     

Seed priming effects on growth,lipid peroxidation,and activity of ROS scavenging enzymes in NaCl-stressed sorghum seedlings from aged seeds

Abstract

The aim of this study was to evaluate growth, lipid peroxidation, and activity of antioxidative enzymes in sorghum seedlings grown under salt stress from artificially aged and primed seeds. The experimental design was completely randomized, with four replications per treatment, in a 2×2×2 factorial arrangement that consisted of eight treatments: two seed vigor levels (aged or not), two seed types (primed or not), and two salinity levels (0 and 100 mM NaCl). In low physiological quality (aged) seeds, the osmoconditioning mitigated the salinity negative effects (NaCl at 100 mM) on seedling growth. The results suggest that osmoconditioning induced an increase in catalase (CAT) and guaiacol peroxidase (POX) activities and these enzymes protected the seedlings against oxidative damage caused by seed accelerated aging and salinity in nutrient solutions. Finally, the observed behavior for superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities suggest that changes in these enzymes in both shoot and roots could do not be induced by studied treatments, because the changes in these organs are unrelated to each other.     

The differential antioxidant capacity of watermelon flesh at different maturity stages and its inhibitory effects on seed aging may explain the significance of fruit flesh colors

Fruit can use different skin colors to attract animals for seed dispersal. Interestingly, however, many fruits such as watermelon, which has a green outer rind, also have colored flesh. The potential reasons underlying this phenomenon were investigated here. White (low maturity), pink (medium maturity), and red-fleshed (high maturity) watermelons were collected and their flesh antioxidant capacities were compared by evaluating Fe³⁺ reducing power and DPPH radical scavenging capacity. Results showed that the antioxidant capacity of fruit flesh at different maturity stages was highest in red flesh, lower in pink flesh, and lowest in white flesh. Moreover, extracts of these flesh samples were obtained and the germination rate and lipid peroxidation of aged seeds, which were pre-treated with these extracts during the artificial aging process, were investigated. This showed that the extracts can significantly increase germination rate, but decrease lipid peroxidation of aged watermelon seeds, with the greatest changes observed with red-flesh extracts and the smallest with white flesh. Dimethyl thiourea, a specific scavenger of free radicals and reactive oxygen species, had a similar effect on the germination rate and lipid peroxidation of aged seeds. Combining previously reported results and our findings, we propose a hypothetical model in which pigment biosynthesis results in the enhancement of antioxidant capacity to illustrate the physiological significance of flesh color on seed aging and germination.     

Change in the reaction of the antioxidant system of wheat sprouts after UV-irradiation of seeds

The response of the antioxidant system of sprouts of wheat Triticum aestivum L. to preliminary irradiation of seeds with UV light was studied. The dependence of lipid peroxidation and the extent of antioxidant activity on the duration of irradiation was studied. It was shown that low doses of UV radiation (5-15 min) stimulate the antioxidant protection of green wheat sprouts grown for eight days. Increasing the irradiation time to 30-60 min leads to the inhibition of lipid peroxidation by the antioxidant system. A more prolonged irradiation of seeds with UV light (for 1-6 h) led to an increase in the level of lipid peroxidation in sprouts. However, 1-2-day-old sprouts from seeds irradiated for 5-6 h, adapted themselves to the influence due to the compensatory mechanisms. By the 8th day of germination of preliminarily irradiated seeds, the content of antioxidants and malone dialdehyde returned to the norm. The dynamics of activity of peroxidase in seeds irradiated with low doses of UV light for 30 min was studied. It was found that on the third day of seed germination, a decrease in peroxidase activity followed by its slight increase occurred. The maximum activity of the enzyme in the endosperm was observed on day 5-6, and in roots and green sprouts, on day 3-5 of germination. It was concluded that antioxidants and peroxidase are involved in the compensatory mechanisms of inhibition of free radicals formed upon UV irradiation of seeds.     

脱水速率对黄皮胚轴脱水敏感性及膜脂过氧化的影响

以黄皮种子离体胚轴为材料,研究了不同干燥速率对胚轴脱水反应和膜脂过氧化的影响.在脱水过程中,胚轴的萌发率、活力指数、电解质渗漏速率,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性逐渐降低,膜脂过氧化产物MDA的含量不断增加.脱水速率愈快,胚轴的半致死含水量就愈低.快速干燥的胚轴能在较低的含水量下存活是因为缩短了在中间含水量下发生的膜脂过氧化作用的时间,以及保持较高的SOD、POD和CAT活性;缓慢干燥的胚轴当与周围环境达到水分平衡后,生活力的丧失将与保持在水分平衡后的时间有关.因此,脱水速率是一种影响顽拗性种子或者胚轴脱水敏感性的重要因子.     

Changes in germinability,lipid peroxidation,and antioxidant enzyme activities in pear stock (<Emphasis Type="Italic">Pyrus betulaefolia</Emphasis> Bge.) seeds during room- and low-temperature storage

The aim of this study was to determine if loss of germinability in Pyrus betulaefolia seeds stored at 4°C and at room temperature is associated with a loss of membrane lipid peroxidation or changes in antioxidant enzyme activities. The results indicated that germination percentage clearly decreased when seeds were stored at room temperature rather than at 4°C from 6 to 12 months. Room-temperature storage of the pear stock seed for 12 months decreased germination to 15.52%, but germination percentage was not changed when seed was stored at 4°C for 12 months. MDA, a marker for membrane lipid peroxidation, increased significantly under room-temperature storage conditions. Antioxidant enzyme (SOD, POD, and CAT) activities were a good indicator of germination percentage in pear stock seeds. Antioxidant enzyme activities of pear stock seeds at 4°C were higher than antioxidant enzyme activities in seeds stored at room temperature from 6 to 12 months. Antioxidant enzyme activities of the pear stock seed decreased markedly under conditions of room-temperature storage from 6 to 12 months. The results of this study showed that long-term room-temperature storage was detrimental for maintaining the vigor of P. betulaefolia seeds. The mechanisms responsible for this outcome are a higher level of membrane lipid peroxidation and a lower level of activity of antioxidant enzymes.     

Carbon Monoxide Alleviates Wheat Seed Germination Inhibition and Counteracts Lipid Peroxidation Mediated by Salinity

Recently In animals, endogenous carbon monoxide （CO）, like nitric oxlde, was implicated as another Important physiological messenger or bioactive molecule. However, little information is known about the physlologlcal roles of CO in the whole plant. In the present study, we report that different concentrations of the 130 donor hematin （0.1, 1.0 and 10.0 μmol/L） alleviated wheat （Tilticum aestivum L. Yangmai 158） seed germination Inhlbltlon caused by 250 mmol/L NaCI stress In a dose-dependent manner. These responses were also proved by the addltion of different gaseous CO aqueous solutions from 0.1% to 100.0% of saturation. Among these treatments, the effect of 1.0 μmol/L hematin and 1.0% saturation of CO aqueous solution were the most obvlous. Furthermore, compared with non-hematin treatment, the degradation of storage reserves In wheat seeds was also accelerated. Time-course analyses showed that application of hematln dose-dependently Increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase activities, thus decreasing the lipid peroxidation In germinating wheat seed subjected to salt stress. Meanwhile, the responses of hematin were specific for CO because the addition of the CO scavenger hemoglobln （0.2 g/L） blocked the various actions of 1.0 μmol/L hematin. Taken together, the results of the present study demonstrate that CO, at a low concentration, is able to attenuate the seed germlnation Inhibition produced by salinity stress and counteract the lipid peroxidation in germinating wheat seeds.     

Free radical scavenging as affected by accelerated ageing and subsequent priming in sunflower seeds

Lipid peroxidation resulting from loss of free radical scavenging is thought to be involved in deterioration of sunflower (Helianthus annuus L.) seeds during accelerated ageing. In other respects, presoaking of seeds in a solution of low water potential (osmopriming) has been demonstrated to reinvigorate aged seeds. The aim of the present work was to study the effect of osmopriming on the germination of aged sunflower seeds and to investigate whether this effect was associated with the restoration of antioxidant defence systems. Seeds were aged for 5 days at 45°C and 100% relative humidity and then primed for various durations up to 7 days at 15°C in a solution of polyethylene glycol 6000 at ?2 MPa. Lipid peroxidation was estimated by measuring malondialdehyde (MDA) and conjugated diene contents, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) were measured throughout the treatments. Accelerated ageing resulted in a marked decrease in the germination rate, and was associated with an increase in the levels of MDA and conjugated dienes, thus indicating lipid peroxidation. Ageing was also characterized by a decrease in the activities of CAT and GR. The activities of SOD and DHAR were much less altered. No APX activity was detected whatever the seed treatment. Priming of aged seeds progressively restored the initial germinative ability and resulted in a marked decrease in the levels of MDA and conjugated dienes, indicating a fall in lipid peroxidation processes. These effects of priming were also well correlated to the recovery of SOD, CAT and GR activities. Priming treatment for 7 days led to full restoration of the cell detoxifying mechanisms which were strongly altered during ageing. Glutathione content showed the same changes as GR activity. There existed a clear-cut relationship between seed germinative energy, expressed as the germination rate, and the efficiency of free radical scavenging systems, in particular CAT and GR activities and glutathione content. The results suggest that the antioxidant defence systems might play a key role in seed vigour.     

脱水方法对棕榈种子萌发及膜脂过氧化的影响

以棕榈种子为材料,比较了硅胶脱水和自然脱水方法下种子萌发特征和膜脂过氧化程度。结果表明:棕榈种子的初始含水量为33.1%,萌发率为83.3%;当硅胶脱水至含水量21.2%时萌发率为80.0%,而自然脱水至23.2%时萌发率仅为56.7%;当含水量降至10%左右时,硅胶脱水萌发率为27.7%,而自然脱水的萌发率为26.7%。在脱水过程中,2种脱水处理种子的浸出液电导率和丙二醛(MDA)含量都呈升高趋势,但自然脱水种子浸出液电导率升高的速率较硅胶脱水快,而MDA含量在硅胶脱水下增加较大。硅胶脱水处理种胚中脯氨酸含量及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性均较自然脱水高,但2种脱水处理种子整体均呈先增加再下降的趋势。研究发现,棕榈种子为中间型种子,其在脱水初期对自然脱水较敏感,而脱水后期脱水速率对其生活力影响较小;棕榈种子对硅胶脱水的脱水敏感较自然性脱水要低,硅胶脱水有利于改善棕榈种子的贮藏寿命。     

The Antioxidant System of Wheat Seeds during Germination

The dynamics of peroxidase activity and antioxidant contents in wheat seeds were studied in the course of 24-hour swelling at 5°C (group 1) and 23°C (group 2). Both parameters were 1.5 times higher in seeds of the first group. In the same seeds, peroxidase activity in the endosperm and seed coat increased by factors of 1.5 and 1.8, respectively. Catalytic constants of wheat seed peroxidase were determined in the reactions of o-dianisidine and ascorbic acid peroxidation. In the pH range studied (pH 5–7), K _m proved to change only slightly. In seedlings, an increase in the lipid peroxidation rate was accompanied by an increase in the content of antioxidants. Peroxidase activity increased as the content of antioxidants decreased, and vice versa. Thus, the reciprocal influence of peroxidase and low-molecular antioxidants during seed germination in wheat was revealed.     

Tocopherol and Organic Free Radical Levels in Soybean Seeds during Natural and Accelerated Aging

Soybean seeds which had aged in long-term storage (“natural aging”) or by exposure to high temperature and humidity (“accelerated aging”) were analyzed for their tocopherol and organic free radical contents. Tocopherol levels remained unchanged during both types of aging. Three principal tocopherol homologues (α, γ, δ) were present in fairly constant proportions throughout. Organic free radical levels were also remarkably stable, presumably due to the relatively immobile environment of the dry seed. These results, taken in conjunction with previous data on the stability of unsaturated fatty acids in soybean seeds, indicate that it is improbable that lipid peroxidation need play a significant role during natural or accelerated aging in this species.