Effect of the citrus flavanone naringenin on oxidative stress in rats

Flavonoids are non-nutrient plant phenolic compounds proposed to provide health benefits in humans. The antioxidant and prooxidant effects of the citrus flavanone naringenin have been tested only in vitro. The dose-response effect of naringenin consumption was tested in weanling rats (n=6-8/group) with a 2x4 factorial design using high or low oxidative stress (Hox or Lox, respectively) diets, created by adequate or deficient amounts of vitamin E and selenium, with three increasing naringenin concentrations (30, 60, or 120 mg/kg of diet). Hox compared to Lox rats exhibited reduced growth and liver hypertrophy, which was not prevented by naringenin consumption. Also, Hox rats exhibited severalfold higher liver NAD(P)H:quinone oxidoreductase-1 activity, which was further elevated in proportion to naringenin intake, but this was not sufficient to protect against oxidative stress indicated by higher liver total aldehydes. In addition, dietary naringenin did not affect antioxidant nutrient status or physiological markers of growth under Lox conditions. Thus, dietary naringenin did not exhibit antioxidant or prooxidant effects in vivo in this rat model.     

Antioxidant activity of dietary oregano essential oil and alpha-tocopheryl acetate supplementation in long-term frozen stored turkey meat

The effects of dietary oregano essential oil and alpha-tocopheryl acetate supplementation on the oxidative stability of long-term frozen stored turkey meat were investigated. Thirty 12-week-old turkeys, randomly divided into five groups, were given a basal diet or a basal diet supplemented with 200 mg of alpha-tocopheryl acetate kg(-1), or 100 or 200 mg of oregano oil kg(-1), or 100 mg of oregano oil plus 100 mg of alpha-tocopheryl acetate kg(-1) for 4 weeks prior to slaughter. Lipid oxidation in breast and thigh meat was assessed after 1, 3, 6, and 9 months of frozen storage at -20 degrees C prior to or following 7 days of refrigerated storage at 4 degrees C. Results showed that oregano oil increased the oxidative stability of breast and thigh meat during the frozen storage. Dietary oregano oil at the inclusion level of 200 mg kg(-1) feed was significantly (p < 0.05) more effective in delaying lipid oxidation compared to the level of 100 mg kg(-1), but equivalent to dietary alpha-tocopheryl acetate supplementation at 200 mg kg(-1), which in turn was inferior to dietary supplementation of 100 mg kg(-1) oregano essential oil plus 100 mg kg(-1) alpha-tocopheryl acetate that was significantly (p < 0.05) superior to all other treatments. Thigh meat was more susceptible to oxidation than breast meat, although the former contained alpha-tocopherol at markedly higher levels. Mean alpha-tocopherol levels in breast and thigh meat from all treatments decreased during the frozen storage, the decrease being sharper between 1 and 3 months of frozen storage for breast and between 3 and 6 months for thigh meat. Oregano oil supplementation increased (p < 0.05) the retention of alpha-tocopherol in meat, the increase being positively correlated with the supplementation level. However, the retention of alpha-tocopherol in meat could only partly elucidate the antioxidant activity exhibited by dietary oregano oil supplementation.     

Blackberry extract attenuates oxidative stress through up-regulation of Nrf2-dependent antioxidant enzymes in carbon tetrachloride-treated rats

The aim of this study was to investigate the protective ability of blackberry extract (BE) against oxidative stress in carbon tetrachloride (CCl(4))-treated rats. The results showed that treatment with BE attenuated lipid peroxidation that was increased by CCl(4) and also markedly recovered the activity of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR), that were decreased by CCl(4). BE also elevated the protein expression levels of NF-E2-related factor-2 (Nrf2), CuZnSOD, MnSOD, GPx-1/2, and heme oxygenase-1 (HO-1), but not that of catalase. Furthermore, the administration of BE significantly attenuated the levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) that were increased by CCl(4). Therefore, the present study suggests that BE possesses significant protective effects against in vivo oxidative stress.     

Behavioral responses of rats exposed to long-term dietary vinclozolin

Vinclozolin is a fungicide used on food crops with human exposure estimated at approximately 2 microg/kg/day from ingestion; occupational exposure, however, may be greater. The metabolites of vinclozolin have been reported to act as antiandrogens and have adverse effects on reproductive physiology and behavior in animals. Here, pregnant rats were fed soy-free diets containing 0, 10, 150, or 750 ppm of vinclozolin (approximately 0, 0.8, 12, and 60 mg/kg/day for an adult) beginning on gestational day 7, and offspring were continued on these diets through sacrifice at postnatal day 77. Male and female offspring were assessed for changes in several nonreproductive sexually dimorphic behaviors: open field and running wheel locomotor activity, play behavior, and consumption of saccharin- and sodium chloride-flavored solutions. There was a significant interaction of sex with vinclozolin exposure on running wheel activity, which indicated that females in the high-dose exposure group were hypoactive compared to same-sex controls. There was a significant overall effect of vinclozolin exposure on fluid consumption, and high-dose animals showed increased intake of the saccharin solution and decreased intake of plain water while saccharin was available. Effects were more pronounced in females, which drank 40.8% more saccharin than control females, whereas males drank 6.2% more than control males. There were no effects of vinclozolin treatment on play behavior or sodium solution intake. Gestational duration, total and live pups per litter, litter sex ratios, and birth weight were also not significantly affected, nor were body weight and food intake for dams and offspring. These results indicate that long-term dietary exposure to vinclozolin does not have severe toxicological consequences on the nonreproductive behaviors measured here. However, exposure may cause subtle alterations in locomotor activity and consumption of saccharin-flavored solution.     

Ameliorative effects of proanthocyanidin on oxidative stress and inflammation in streptozotocin-induced diabetic rats

Recent evidence strongly suggests that oxidative stress due to redox imbalance is causally associated with inflammatory processes and various diseases including diabetes. We examined the effects of proanthocyanidin from persimmon peel, using both oligomers and polymers, against oxidative stress with elucidation of the underlying mechanisms in streptozotocin-induced diabetic rats. The elevation of lipid peroxidation in the kidney and serum under the diabetic condition was decreased by the administration of proanthocyanidin. The suppression of reactive oxygen species generation and elevation of the reduced glutathione/oxidized glutathione ratio were observed in the groups administered proanthocyanidin. These results support the protective role of proanthocyanidin from oxidative stress induced by diabetes. Moreover, proanthocyanidin, especially its oligomeric form, affected the inflammatory process with regulation of related protein expression, inducible nitric oxide synthase, cyclooxygenase-2, and upstream regulators, nuclear factor kappaB, and inhibitor-binding protein kappaB-alpha. Proanthocyanidin ameliorated the diabetic condition by decreases of serum glucose, glycosylated protein, serum urea nitrogen, urinary protein, and renal advanced glycation endproducts. In particular, oligomeric proanthocyanidin exerted a stronger protective activity than the polymeric form. This suggests that the polymerization of proanthocyanidin has an effect on its protective effect against diabetes. The present study supports the beneficial effect of proanthocyanidin against diabetes and oxidative stress-related inflammatory processes.     

Effect of curcumin on inflammation and oxidative stress in cisplatin-induced experimental nephrotoxicity

Nephrotoxicity is a major complication and a dose limiting factor for cisplatin therapy. Recent evidence suggests that inflammation and oxidative stress may contribute to the pathogenesis of cisplatin-induced acute renal failure. Curcumin is claimed to be a potent anti-inflammatory and antioxidant agent. The present study was performed to explore the effect of curcumin against cisplatin-induced experimental nephrotoxicity. Curcumin in the dosages of 15, 30, and 60 mg kg(-1) was administered 2 days before and 3 days after cisplatin administration. Renal injury was assessed by measuring serum creatinine, blood urea nitrogen, creatinine, urea clearance, and serum nitrite levels. Renal oxidative stress was assessed by determining renal malondialdehyde levels, reduced glutathione levels and enzymatic activities of superoxide dismutase and catalase. Systemic inflammation was assessed by tumor necrosis factor-alpha (TNF-alpha) levels. A single dose of cisplatin resulted in marked inflammation (486% rise in TNF-alpha level) and oxidative stress and significantly deranged renal functions as well as renal morphology. The serum TNF-alpha level was markedly reduced in curcumin-treated rats. Curcumin treatment significantly and dose-dependently restored renal function, reduced lipid peroxidation, and enhanced the levels of reduced glutathione and activities of superoxide dismutase and catalase. The present study demonstrates that curcumin has a protective effect on cisplatin-induced experimental nephrotoxicity, and this effect is attributed to its direct anti-inflammatory and strong antioxidant profile. Hence, curcumin has a strong potential to be used as a therapeutic adjuvant in cisplatin nephrotoxicity.     

Effect of dietary dried tomato pulp on oxidative stability of Japanese quail meat

Ninety, 21-day-old, Japanese quail (Coturnix coturnix japonica) divided into three groups with five subgroups each were fed a basal diet that served as control or a basal diet containing 5 or 10% of dried tomato pulp (DTP), a byproduct of the tomato-processing industry. The DTP contained lycopene and beta-carotene at 281 and 24.3 mg kg(-)(1) of dry weight, respectively. On day 42 of age, birds were slaughtered, and carcasses were trimmed for breast meat. To assess the effect of dietary treatment on the oxidative stability of raw and cooked meat, raw meat was subjected to iron-induced lipid oxidation, whereas both raw and cooked meats were subjected to refrigerated storage at 4 degrees C. The extent of lipid oxidation was determined on the basis of the malondialdehyde (MDA) formed through the use of third-order derivative spectrophotometry. Results showed that after 6 and 9 days of refrigerated storage, MDA values in raw meat were increased. The increase was higher (P < 0.05) for the 10% DTP group and lower (P < 0.05) for the 5% DTP group, compared to control. An analogous oxidation profile was observed for cooked meat at 3, 6, and 9 days of storage. Iron-induced lipid oxidation of raw meat showed that the 10% DTP group as well as the control group exhibited MDA values that did not differ (P > 0.05) from each other at all time points, whereas the 5% DTP group presented MDA values that, although not differing from those of the other groups at 0 and 50 min, were significantly (P < 0.05) lower than those of the other groups at 100 and 150 min of iron-induced lipid oxidation. These results suggested that inclusion of dried tomato pulp in feed at a level of 5% exerted an antioxidant effect, whereas addition at level of 10% exerted a prooxidant effect. Mean alpha-tocopherol levels in the control, 5% DTP, and 10% DTP groups were 2.2, 2.1, and 1.4 mg kg(-)(1) of meat, respectively. Fatty acid analysis showed that the 10% DTP group had a higher (P < 0.05) content of total polyunsaturated fatty acids and a greater (P < 0.05) unsaturated/saturated fatty acid ratio compared to control. There might be an interaction between DTP and alpha-tocopherol that is of importance for the balance between pro- and antioxidative activities. Future experiments should be designed to explore the interaction between individual carotenoids and tocopherols in order to better elucidate their role in oxidative changes.     

Effect of silicon on the alleviation of boron toxicity in wheat growth,boron accumulation,photosynthesis activities,and oxidative responses

Little is known about the alleviation of boron (B) toxicity in wheat induced by silicon (Si), especially on the photosynthesis properties and antioxidative responses. The purpose of this research was to evaluate the effect of Si on the toxicity of B in wheat and the related mechanisms. A greenhouse pot experiment was conducted using wheat (Triticum aestivum Linn.) at the early seedling stage. Boric acid was added to soil to create three B concentrations. Each B treatment consisted of two Si treatment including control and Si application. Our results show that Si has an alleviative effect on B toxicity in wheat plant. Si showed significant alleviative effect on wheat growth at 150 mg B kg^?1 whereas did not show significant alleviative effect at 300 mg B kg^?1. Under B stress, plant dry weight of wheat was reduced and the reduction was alleviated by Si. However, plant tissue B accumulation was not reduced by the application of Si. Net photosynthetic rates of wheat were not influenced significantly by B or Si. The oxidative damages in wheat that were caused by excess B were not significantly alleviated by Si. These results suggest that the effect of Si on B toxicity in wheat is still controversial and more studies need to be conducted.     

长期撂荒对黑土土壤有机碳组分的影响

为明确长期撂荒对黑土不同土层土壤有机碳及其组分的影响,以吉林公主岭黑土长期定位试验为对象,选取不施肥和撂荒2个处理,采用改良的Walkley-Black土壤有机碳分组方法,研究不同层次(0～0.2、0.2～0.4和0.4～0.6 m)土壤有机碳及其组分的变化.结果表明:(1)0～0.6 m土壤剖面中,撂荒处理下土壤有机...     

长期施肥对棕壤有机碳组分的影响

对起始于1979年的棕壤长期肥料定位试验田2005年的耕层土壤不同有机碳组分进行了测定与分析,以探讨长期施肥影响土壤有机碳的过程及机理。结果显示:长期单施化肥降低了土壤的游离态颗粒有机碳（FPOM-C）含量,但进一步稳定了矿物结合态有机碳(MOM-C),最终提高了土壤总有机碳(TOC)含量;长期施用有机肥和有机肥配施化肥使土壤的FPOM-C、闭蓄态颗粒有机碳(OPOC)、MOM-C以及含量均显著提高,且增加效果好于单施化肥。从各组分有机碳所占比例或相对比值来看,长期施用有机肥和有机肥配施化肥提高了POM-C/TOC比例而降低了MOM-C/TOC比例,使FPOM-C/OPOM-C比值显著增大。表明土壤有机碳结构分组的应用有助于揭示长期施肥影响土壤有机碳的机理。     

稀土对缓解油菜镉胁迫的研究

长期利用污水灌溉、污泥改良土壤以及化学农药和化肥的不合理施用,会使农用土壤受到重金属不同程度的污染[1] ,且以重金属镉(Cd)污染最为普遍关注.     

长期施肥对栗褐土有机碳矿化的影响

【目的】 土壤有机碳矿化是土壤中重要的生物化学过程,与土壤养分的释放、土壤质量的保持以及温室气体的形成密切相关。本文以 25 年长期定位施肥试验为依托,对栗褐土土壤有机碳矿化速率、有机碳累积矿化量的动态变化进行研究,为科学管理土壤肥力、增加栗褐土碳汇、减少温室气体排放提供依据。 【方法】 田间试验开始于 1988,共设置 8 个施肥处理:不施肥 (CK);单施氮肥 (N);氮磷肥合施 (NP);单施低量有机肥(M₁);低量有机肥与氮肥合施 (M₁N);低量有机肥与氮磷肥合施(M₁NP);高量有机肥与氮肥合施 (M₂N);高量有机肥与氮磷肥合施 (M₂NP)。于 2013 年玉米播种前,采集耕层 (0—20 cm) 土壤样品,采用室内培养方法,对土壤碳矿化释放 CO₂ 的数量和速率进行测定,并利用一级动力学方程计算出土壤有机碳库潜在矿化势和周转速率。 【结果】 各肥料处理不同程度地提高了栗褐土总有机碳含量,以高量有机肥与化肥配施作用最为显著。与 CK 相比,M₂N、M₂NP 处理土壤总有机碳含量增加了 121.1%、166.8%。不同处理土壤样品培养有机碳矿化速率均在第一天达到峰值,随后急剧下降。5 d 后,下降趋缓,不同处理 CO₂ 产生速率趋于一致。培养期间,各处理矿化速率变化符合对数函数关系。长期施用不同肥料均可以提高栗褐土有机碳的矿化速率,其大小顺序为:有机肥与化肥配施 > 单施有机肥 > 单施化肥 > 对照。培养 57 d 后,各处理土壤有机碳累积矿化量为 555.0～980.3 mg/kg,以 M₂NP、M₁N 的累积量较高,为对照的 1.77 倍、1.73 倍。长期施肥栗褐土有机碳矿化率呈下降趋势,以处理 M₂NP 下降最明显,与对照相比,降低了 6.3 个百分点。施肥处理土壤的潜在矿化势均高于对照,M₁N、M₂NP 最高,为 923.7 mg/kg 和 926.4 mg/kg,较对照增加了 74.0% 和 74.5%。不同施肥处理均可明显提升土壤有机碳的周转速率,减少周转时间,其中处理 M₁NP、M₂NP 效果最为明显。 【结论】 长期施用化肥、有机肥及有机无机肥配施可有效促进栗褐土有机碳的积累,提高有机碳的矿化速率和周转速率,降低有机碳的矿化率 (累积矿化量占有机碳总量的比率),加强了土壤的固碳能力,以 M₂NP 处理的效果更佳。      

Hypoglycemic activity of Gymnema sylvestre extracts on oxidative stress and antioxidant status in diabetic rats

Diabetes mellitus, which is associated with oxidative damage, has a significant impact on health, quality of life, and life expectancy. An ethanol extract of Gymnema sylvestre leaf was examined in vitro and in vivo to investigate the role of antioxidants in diabetic rats. The extract exhibited strong antioxidant activity in the assays, including TBA (56%), SOD-like (92%), and ABTS (54%). Blood glucose levels in the diabetic rats fed G. sylvestre extract decreased to normal levels. The presence of the antihyperglycemic compounds gymnemagenin and gymnemic acids in G. sylvestre extract was detected by LC/MS analysis. Lipid peroxidation levels were decreased by 31.7% in serum, 9.9% in liver, and 9.1% in kidney in the diabetic rats fed the extract. Feeding G. sylvestre extract to the diabetic rats decreased the activity of glutathione peroxidase in cytosolic liver and glutamate pyruvate transaminase in serum to normal levels.     

耕作方式对长期免耕农田土壤微生物生物量碳的影响

以华北冬小麦-夏玉米两熟区长期免耕土壤为研究对象, 研究不同耕作方式(免耕、翻耕和旋耕)对长期免耕土壤微生物生物量碳(SMBC)的影响, 为制定合理的轮耕制度提供依据。试验结果表明: 长期免耕土壤进行耕作处理后SMBC 的时空分布和稳定性产生显著变化。不同耕作处理SMBC 含量在0~5 cm 和5~10 cm 土层变化明显, 小麦起身期含量最低, 收获期最高; 深层SMBC变化不明显。免耕处理SMBC 随土壤层次明显降低, 且各土壤层次SMBC 差异达显著(P<0.05)水平; 翻耕、旋耕处理0~5 cm 和5~10 cm 土层间SMBC 无明显差异, 其他层次间差异显著(P<0.05)。从生育期平均值看, 0~5 cm 土层免耕处理SMBC 含量较高, 翻耕和旋耕处理则分别比免耕降低6.7%、6.1%; 与免耕相比, 5~10 cm 土层SMBC 翻耕、旋耕处理分别增加30.2%和20.7%(P<0.01),10~20 cm 土层SMBC 翻耕、旋耕处理比免耕增加48.1%(P<0.01)和10.5%(P<0.05)。在冬小麦生育期内, 0~20 cm土层SMBC 稳定性表现为翻耕>旋耕>免耕, 20~30 cm 土层SMBC 稳定性表现为免耕>翻耕>旋耕。     

长期保护性耕作对黄绵土总有机碳和易氧化有机碳动态的影响

长期定位试验研究了黄土高原西部旱农区不同耕作措施(传统耕作T、免耕+秸秆覆盖NTS、免耕NT、传统耕作+秸秆翻埋TS、传统耕作+地膜覆盖TP和免耕+地膜覆盖NTP)对黄绵土土壤总有机碳和易氧化有机碳的影响。结果表明, 土壤有机碳含量随土壤深度的增加而降低, 10~30 cm土层土壤有机碳含量的下降较为明显, 并且在0~5 cm、5~10 cm和10~30 cm土层中, 均表现为由研究初期各处理相对差异较小到试验中后期各处理出现显著差异的变化。不同耕作措施下0~30 cm土壤总有机碳和易氧化有机碳在2002-2012年的平均含量均为NTS>TS>NTP>NT>T>TP。与传统耕作相比, 免耕各处理和传统耕作秸秆翻埋处理可增加1.2%~7.2%的土壤总有机碳, 5.3%~16.6%的土壤易氧化有机碳含量, 而传统耕作覆膜处理分别降低4.3%和2.7%。免耕和秸秆覆盖处理均有利于黄绵土土壤有机碳和易氧化有机碳的积累, 免耕结合秸秆覆盖效果最佳, 而多年传统耕作覆盖地膜后有机碳明显降低。免耕秸秆覆盖处理土壤总有机碳和易氧化有机碳含量平均值在2004年、2006年、2008年、2010年及2012年分别较2002年提高9.5%和42.9%、13.2%和67.6%、21.5%和71.5%、1.1%和15.9%、2.7%和12.6%。因此, 在西部黄土高原黄绵土区, 采用免耕结合秸秆覆盖的保护性耕作措施有利于土壤总有机碳和易氧化有机碳含量的提高, 从而有利于土壤质量的持续改善。易氧化有机碳对不同耕作措施的响应比总有机碳更灵敏, 可以将其作为指示黄绵土有机碳变化的早期指标。     

Protection against oxidative stress in diabetic rats by wheat bran feruloyl oligosaccharides

Diabetes is one of the most costly of the chronic diseases and is increasing in epidemic proportions in developing countries. It has been found that some antioxidants play a role in protection against oxidative stress, which is associated with diabetes. In this study, enzyme-released feruloyl oligosaccharides from wheat bran were given intragastrically (ig) to test their effect on antioxidant capacity, body weight restoring capacity, and serum glucose level in alloxan-induced diabetic Sprague-Dawley (SD) rats, using sodium ferulate and vitamin C as positive control groups. The levels of blood glucose, total antioxidant capacity (TAOC), and malondiadehyde (MDA) and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and xanthine oxidase (XOD) were determined in rat serum, liver, and testes. Feruloyl oligosaccharides significantly increased TAOC level, GSH-Px, and SOD activities, but decreased blood glucose and MDA levels and XOD activity in serum, liver, and testes of diabetic rats compared to diabetic controls. Feruloyl oligosaccharides were, overall, more efficient in mitigating oxidative damage in diabetic rats than sodium ferulate and vitamin C. In this feruloyl oligosaccharide feeding study, the antioxidant restoring capacity varied across the tissues observed, and also the activity change of the various antioxidant enzymes varied within a single tissue. Feruloyl oligosaccharides showed greater antioxidant capacity in vivo than in vitro when compared with vitamin C.     

施钙对甘薯铝胁迫的缓解效应

采用土培试验方法,以铝敏感型甘薯品种商薯19号为研究材料,设置不同的钙处理水平(0、0.8、1.6、2.4 g/kg),研究了钙对甘薯铝胁迫(1 g/kg)的缓解效应。结果表明:施钙可以显著促进甘薯根系的生长发育,提高叶片叶绿素含量和PSⅡ(PhotosystemⅡ)最大光化学效率(Fv/Fm),提高叶片中超氧化物歧化酶、过氧化氢酶和过氧化物酶活性,降低叶片中丙二醛的积累量。施钙可以有效提高甘薯对铝胁迫的抗逆性,有效缓解铝对甘薯的胁迫。     

不同施肥管理对红壤性水稻土有机碳、氮形态的影响

A long-term experiment beginning in 1981 in Jinxian County of Jiangxi Province, subtropical China, was conducted in a paddy field under a double rice cropping system with four different fertilization regimes, including 1) no fertilizer as control (CK), 2) balanced chemical N, P, and K fertilizers (NPK), 3) organic manure using milk vetch and pig manure in the early and late rice growing season, respectively (OM), and 4) balanced chemical fertilizers combined with organic manure (NPKM). Samples (0-17 cm) of the paddy field soil, which was derived from Quaternary red clay, were collected after the late rice harvest in November 2003 for determination of total organic carbon (TOC) and total nitrogen (TN) and fractions of organic C and N. Results showed that TOC and TN in the NPKM and OM treatments were significantly higher than those in other two treatments (CK and NPK). Application of organic manure with or without chemical fertilizers significantly increased the contents of all fractions of organic C and N, whereas chemical fertilizer application only increased the contents of occluded particulate organic C (oPOC) and amino acid N. In addition, application of organic manure significantly enhanced the proportions of free particulate organic carbon (fPOC) and oPOC in total C, and those of amino sugar N and amino acid N (P < 0.01) in total N. In contrast, chemical fertilizer application only increased the proportions of oPOC and amino acid N (P < 0.05). There were no significant differences in either contents or proportions of soil organic C and organic N fractions between the NPKM and OM treatments. These indicated that organic manure application with or without chemical fertilizers played the most significant role in enhancing soil organic C and N quantity and quality in the paddy field studied.     

长期施肥对栗褐土有机碳含量及其组分的影响

【目的】作为土壤质量的重要指标,土壤有机碳及其组分在耕地生产力和作物产量方面发挥着重要作用。本文以25年长期定位施肥试验为依托,分析了不同施肥处理对栗褐土有机碳含量及其组分的影响,为调控农田土壤肥力及栗褐土有机碳库的管理提供科学依据。【方法】田间试验开始于1988年,设置8个施肥处理为不施肥(CK);单施氮肥(N);氮磷肥合施(NP);单施低量有机肥(M1);低量有机肥与氮肥合施(M1N);低量有机肥与氮磷肥合施(M1NP);高量有机肥与氮肥合施(M2N);高量有机肥与氮磷肥合施(M2NP)。于第25年玉米播种前,采集以上处理的耕层(0—20 cm)土壤样品。借助有机碳物理分组方法和化学分析方法,测定了土壤总有机碳和有机碳各组分的含量。【结果】长期施用不同肥料不同程度地提高了栗褐土总有机碳、游离态颗粒有机碳以及闭蓄态颗粒有机碳含量,其中有机肥与化肥配施尤其是高量有机肥与化肥配施的作用更加明显。与不施肥相比,高量有机肥与无机肥配施(M2N、M2NP)总有机碳含量增加了121.1%、166.8%,游离态颗粒有机碳增加了239.2%、359.2%,闭蓄态颗粒有机碳增加了288.4%、289.9%。单施氮肥(N)及有机肥与氮磷肥配施(M1NP、M2NP)可显著提高矿物结合态有机碳含量,增幅分别为27.8%、34.8%、33.3%。不施肥条件下,栗褐土有机碳中颗粒有机碳与矿物结合态有机碳所占的比例相当,长期施肥提高了颗粒有机碳特别是闭蓄态颗粒有机碳的比例,降低矿物结合态有机碳所占的比例,闭蓄态颗粒有机碳成为栗褐土有机碳的主要贮存库。相关分析表明,长期施肥条件下栗褐土游离态、闭蓄态颗粒有机碳含量之间及其与总有机碳含量之间均呈极显著正相关,矿物结合态有机碳含量与总有机碳及其他组分的有机碳之间均无明显相关。【结论】化肥、有机肥以及有机肥与化肥配施能够提高栗褐土游离态颗粒有机碳、闭蓄态颗粒有机碳以及总有机碳含量。高量有机肥与化肥配施更有助于栗褐土游离态、闭蓄态颗粒有机碳的积累,有利于土壤养分有效性的提高和有机碳品质的改善。氮肥单施、有机肥与氮磷肥配施则是提高矿物结合态有机碳含量的有效措施。     

外源甘氨酸对镉胁迫下苜蓿幼苗生长和氧化损伤的影响

以苜蓿为试验材料,分析了甘氨酸处理对幼苗镉(Cd)毒害缓解的生理机制。Cd毒害降低了苜蓿幼苗超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,导致幼苗出现氧化伤害,如丙二醛(MDA)含量升高,伊文斯蓝(Evans blue)染色加深。甘氨酸处理提高了苜蓿幼苗SOD和CAT活性,降低了MDA的累积,减少了氧化伤害。Cd毒害还降低了幼苗硝酸还原酶(NR)活性,外源甘氨酸处理则显著提高其NR活性。施用NR抑制剂钨酸钠降低了苜蓿幼苗的NR活性,同时抵消了甘氨酸对Cd胁迫幼苗的生长缓解作用。表明甘氨酸通过提高苜蓿幼苗的抗氧化能力和NR活性,从而提高幼苗对Cd胁迫的耐受性。