Altered Expression of Transcription Factor Genes in Rice Flag Leaf under Low Nitrogen Stress

The response of transcription factor genes to low nitrogen stress was studied to provide molecular basis for improving the absorption and utilization efficiency of nitrogen fertilizer in rice. The agilent rice genome arrays were used to study the varied expression of transcription factor genes in two rice varieties （SN 196 and Toyonishhiki） with different chlorophyll contents under low nitrogen stress. The results showed that a total of 53 transcription factor genes （35 down-regulated and 18 up-regulated genes at the transcription level） in flag leaves of super-green rice SN196 and 27 transcription factor genes （21 down-regulated and 6 up-regulated genes at the transcription level） in flag leaves of Toyonishiki were affected by low nitrogen stress. Among those nitrogen-responsive genes, 48 transcription factor genes in SN196 and 22 in Toyonishiki were variety-specific. There were overlapped transcription factor genes responded to low nitrogen stress between SN196 and Toyonishiki, with 1 up-regulated and 4 down-regulated at the transcription level. Distributions of low nitrogen responsive genes on chromosomes were different in two rice varieties.

Comparative analysis of metabolite changes in two contrasting rice genotypes in response to low-nitrogen stress

Identification of metabolites responsible for tolerance to low nitrogen availability(low-N)will aid in the genetic improvement of rice yield under nitrogen deficiency.In this study,a backcross introgression line(G9)and its recurrent parent Shuhui 527(SH527),which show differential responses to low-N stress,were used to identify metabolites associated with lowN tolerance in rice.Differences in metabolite contents in the leaves of G9 and SH527 at three growth stages under low-N stress were assessed by gas chromatography–mass spectrometry.Many metabolites,including amino acids and derivatives,were highly enriched in G9 compared with SH527 under the control condition,suggesting that the two genotypes had basal metabolite differences.Low-N stress induced genotype-specific as well as growth stagedependent metabolite changes.Metabolites induced specifically in G9 that were involved in glycolysis and tricarboxylic acid metabolism were enriched at the tillering and grain filling stages,and metabolites involved in nitrogen and proline metabolism were enriched at the booting stage.Enrichment of pyroglutamate,glutamate,2-oxoglutarate,sorbose,glycerate-2-P,and phosphoenolpyruvic acid in G9 suggests that these metabolites could be involved in low-N stress tolerance.The results presented here provide valuable information for further elucidation of the molecular mechanisms of low-N tolerance in crops.

Effects of dietary arginine levels on growth performance,body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish(Pelteobagrus fulvidraco)

This experiment was conducted to investigate the effects of dietary arginine levels on growth performance, body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish(Pelteobagrus fulvidraco). Five isonitrogenous and isolipidic diets(42%protein and 9% lipid) were formulated to contain graded levels of arginine(2.44%, 2.64%, 2.81%, 3.01% and3.23% of diet), by supplementing L-Arginine HCI. Seven hundred juvenile yellow catfish with an initial average body weight of 1.13 ± 0.02 g were randomly divided into 5 groups with 4 replicates of 35 fish each and each group was fed one of the diets. After 56 d feeding, fish were exposed to 100 mg/L of ammonia-nitrogen for 72 h. The results showed that weight gain(WG) and specific growth rate(SGR) in2.64% and 2.81% groups were significantly higher than those in 3.23% group(P < 0.05). The feed conversation ratio(FCR) in 2,64%, 2,81% and 3.01% groups was significantly decreased when compared with3,23% group. The protein efficiency ratio(PER) in 2.64% group was significantly higher than that in 2.44%and 3.23% groups(P < 0.05). The condition factor(CF) of fish was significantly higher in 2.81% group than that in 2,44% group(P < 0.05). Dietary arginine levels had no significant effect on hepatosomatic index(HSI), viscerosomatic index(VSI), and whole-body dry matter, crude protein, crude lipid, ash contents, as well as serum total protein(TP), triglyceride(TG), glucose(GLU), urea nitrogen(UN) contents and aspartate aminotransferase(AST), alanine aminotransferase(ALT) activities(P> 0.05). After the fish were challenged to ammonia-nitrogen for 72 h, their cumulative mortality rate in 2.81% group was significantly lower than that in 2.44% group(P < 0.05). The results suggested that dietary arginine level at 2.81%could optimize anti-ammonia-nitrogen stress ability of juvenile yellow catfish and a level of 3.23%arginine seemed to depress the growth performance of fish and decreased their tolerance to the ammonia-nitrogen stress under current study. A quadratic regression analysis based on WG indicated that the optimal dietary arginine requirement of juvenile yellow catfish was estimated to be 2.74% of the diet(6.45% of dietary protein) under current culture conditions.

Protein differential expression in the elongating cotton (Gossypium hirsutum L.) fiber under nitrogen stress

Nitrogen (N) is an essential macronutrient and an important factor limiting agricultural productivity. N deficient or excess conditions often occur during the cotton growth season and incorrect N application may affect cotton fiber yield and quality. Here, the influence of N stress on the cotton fiber proteome was investigated by two-dimensional gel electrophoresis and mass spectrometry. The results indicated that N application rate affects nitrogen accumulation in fiber cells and fiber length. The proteins differentially expressed during N stress were mainly related to plant carbohydrate metabolism, cell wall component synthesis and transportation, protein/amino acid metabolism, antioxidation and hormone metabolism. The most abundant proteins were C metabolism-related. Ten days post anthesis is a critical time for fiber cells to perceive environmental stress and most proteins were suppressed in both N deficient and N excess conditions at this sampling stage. However, several N metabolism proteins were increased to enhance N stress tolerance. Excess N may suppress carbohydrate/energy metabolism in early fiber development much like N deficiency. These results have identified some interesting proteins that can be further analyzed to elucidate the molecular mechanisms of N tolerance.

The Relative Importance of Nitrogen vs. Moisture Stress May Drive Intraspecific Variations in the SLA-RGR Relationship: The Case of <i>Picea mariana</i>Seedlings

Plants acclimate to nitrogen (N) or moisture stress by respectively increasing photosynthetic N use efficiency (PNUE) or water use efficiency (WUE), in order to maximize their relative growth rate (RGR). These two phenotypic adaptations have opposite effects on specific leaf area (SLA). Thus, intraspecific variations in the SLA-RGR relationship should reflect the relative importance of N vs. moisture stress in plants. In this study, we measured needle gas exchanges and N concentrations in order to derive PNUE and WUE, as well as SLA and RGR of black spruce (Picea mariana) seedlings growing on a rapidly drained site in the presence or absence of Kalmia angustifolia. The eradication of Kalmia had resulted in a ~140% increase in seedling growth over a 6 year period. We found a negative SLA-RGR relationship where Kalmia had been eradicated, and a positive one where Kalmia had been maintained. Kalmia eradication resulted in higher WUE when measurements were made directly on the seedlings, and in lower PNUE when twigs were rehydrated prior to gas exchange measurements. Our data suggest that the bigger seedlings on Kalmia-eradicated plots increase RGR by decreasing SLA, as a means of coping with moisture stress. By contrast, increasing SLA on noneradicated plots may be a means of coping with nutrient stress exerted by Kalmia. The SLA-RGR relationship could potentially be used to identify the limiting resource for black spruce seedlings in different environments.

Weakened carbon and nitrogen metabolisms under post-silking heat stress reduce the yield and dry matter accumulation in waxy maize

Post-silking high temperature is one of the abiotic factors that affects waxy maize(Zea mays L. sinensis Kulesh) growth in southern China. We conducted a pot trial in 2016–2017 to study the effects of post-silking daytime heat stress(35°C) on the activities of enzymes involved in leaf carbon and nitrogen metabolisms and leaf reactive oxygen species(ROS) and water contents. This study could improve our understanding on dry matter accumulation and translocation and grain yield production. Results indicated that decreased grain number and weight under heat stress led to yield loss, which decreased by 20.8 and 20.0% in 2016 and 2017, respectively. High temperature reduced post-silking dry matter accumulation(16.1 and 29.5% in 2016 and 2017, respectively) and promoted translocation of pre-silking photoassimilates stored in vegetative organs, especially in leaf. The lower leaf water content and chlorophyll SPAD value, and higher ROS(H2O2 and O2^-·) content under heat stress conditions indicated accelerated senescent rate. The weak activities of phosphoenolpyruvate carboxylase(PEPCase), Ribulose-1,5-bisphosphate carboxylase(Ru BPCase), nitrate reductase(NR), and glutamine synthase(GS) indicated that leaf carbon and nitrogen metabolisms were suppressed when the plants suffered from a high temperature during grain filling. Correlation analysis results indicated that the reduced grain yield was mainly caused by the decreased leaf water content, weakened NR activity, and increased H2O2 content. The increased accumulation of grain weight and post-silking dry matter and the reduced translocation amount in leaf was mainly due to the increased chlorophyll SPAD value and NR activity. Reduced PEPCase and Ru BPCase activities did not affect dry matter accumulation and translocation and grain yield. In conclusion, post-silking heat stress down-regulated the leaf NR and GS activities, increased the leafwater loss rate, increased ROS generation, and induced pre-silking carbohydrate translocation. However, it reduced the post-silking direct photoassimilate deposition, ultimately, leading to grain yield loss.

Stress Corrosion Cracking of Nitrogen-containing Stainless Steel 316LN in High Temperature Water Environments

Stress corrosion cracking （SCC） of stainless steels and Ni-based alloys in high temperature water coolant is one of the key problems affecting the safe operation of nuclear power plants （NPPs）. The nitrogen-added stainless steel is a kind of possible candidate materials for mitigating SCC since reducing the carbon content and adding nitrogen to offset the loss in strength caused by the decrease in carbon content can mitigate the problem of sensitization. However, the reports of SCC of nitrogen-added stainless steels in high temperature water are few available. The effects of applied potential and sensitization treatment on the SCC of a newly developed nitrogen-containing stainless steel （SS） 316LN in high temperature water doped with chloride at 250 ℃ were studied by using slow strain rate tests （SSRTs）. The SSRT results are compared with our data previously published for 316 SS without nitrogen and 304NG SS with nitrogen, and the possible mechanism affecting the SCC behaviors of the studied steels is also discussed based on SSRT and microstucture analysis results. The susceptibility to cracking of 316LN SS normally increases with increasing potential. The susceptibility to SCC of 316LN SS was less than that of 316 SS and 304NG SS. Sensitization treatment at 700℃ for 30 h showed little effect on the S CC of 316LN S S and significant effect on the S CC of 316 S S. The predominant cracking mode for the 316LN S S in both annealed state and the state after the sensitization treatment was transgranular. The presented conditions of mitigating stress corrosion cracking are some useful information for the safe use of 316LN SS in NPPs.

Physiological Mechanism of Nitrogen Mediating Cotton (<i>Gossypium hirsutum</i>L.) Seedlings Growth under Water-Stress Conditions

The objective of this investigation was to study the effects of nitrogen on tolerance to water-stress in cotton (Gossypium hirsutum L.) seedlings. Growth chamber studies with pots of washed sand were carried out in Fayetteville, USA, and Nanjing, Chinawith three water conditions (well-watered, drought-stressed, and waterlogging), and three nitrogen rates, low nitrogen (16 mM, approximately 224 mg N·l–1 water), medium nitrogen (24 mM, approximately 448 mg N·l–1 water) and high nitrogen (32 mM, approximately 672 mg N·l–1 water), respectively. The results showed that water-stress treatments reduced plant biomass, C/N ratio, root vigor and leaf photosynthesis (Pn). The plant response to water-stress resistance was affected by nitrogen, and was correlated with the activities of antioxidant enzymes. The changes of anti-oxidant enzymes was the highest in the low nitrogen rate in the drought-stressed and waterlogged cotton seedlings. Malondialdehyde (MDA) content increased significantly in the water-stress treatments, and was the lowest in the low nitrogen rate. There was a significant reduction of N accumulation under water stress. Low-nitrogen treatmentincreased C accumulation, while high-nitrogen treatment decreased N accumulation. Root vigor was decreased by water stress, and was highest in the low-nitrogen rate. After terminating the water stress, N application promoted root vigor, especially in waterlogged seedlings. The trends of Pn weresimilarto that of root vigor. These results suggested that low N application may contribute to cotton drought tolerance by enhancing the activity of antioxidant enzymes and conse-quently decreasing lipid peroxidation, and enhancing root vigor. However, higher N should be applied to waterlog- ging-stressed cotton seedlings after terminating waterlogging.

Effects of nitrogen nutritional stress on the morphological and yield parameters of tomato(Solanum lycopersicum L.)

This investigation was carried out to better understand the effects of nitrogen stress on the growth and yield of tomato （Solanum lycopersicon L.）. Seeds of S. lycopersicon （Ife No. 1 variety） were collected from the Osun-State Ministry of Agriculture, Oshogbo, Nigeria and planted in analyzed top soil. The plants were grown for a period of five weeks within which they were supplied with water and kept under optimum environmental conditions that enhanced normal growth. After this period, the plants were subjected to different levels of nitrogen stress which include： plants supplied with dis- tilled water only （n）, plants supplied with complete nutrient solution （N）, plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 5 （N5）, and plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 10 （N10）. Analysis of Variance （ANOVA） results shows that there is no significant effect of stress on the growth and morphological parameters of tomato plants. However, there was a significant effect of nitrogen stress on the yield parameters. Nitrogen stress also caused an increase in the number and size of fruits produced in plants subjected with high nitrogen concentration.

Increase of nitrogen to promote growth of poplar seedlings and enhance photosynthesis under NaCl stress

The solution culture method was used to study the effect of increasing nitrogen on the growth and pho-tosynthesis of poplar seedlings under 100 mmol L-1 NaCl stress. I Increase in nitrogen reduced stomatal limitation of leaves under NaCl stress, improved utilization of CO2 by mesophyll cells, enhanced photosynthetic carbon assimi-lation capacity, significantly alleviated saline damage of NaCl, and promoted the accumulation of aboveground and root biomass. I Increased nitrogen enhanced photochemical efficiency (ΦPSⅡ) and electron transport rates, relieved the reduction of maximum photochemical efficiency (Fv/Fm) under NaCl, and reduced the degree of photoinhibition caused by NaCl stress. Increased nitrogen applications reduced the proportion of energy dissipating in the form of ineffective heat energy and hence a greater proportion of light energy absorbed by leaves was allocated to photo-chemical reactions. Under treatment with increased nitro-gen, the synergistic effect of heat dissipation and the xanthophyll cycle in the leaves effectively protected pho-tosynthetic PSⅡ and enhanced light energy utilization of leaves under NaCl stress. The increased nitrogen promoted photosynthetic electron supply and transport ability under NaCl stress evident in enhanced functioning of the oxygen-evolving complex on the electron donor side of PS Ⅱ. It increased the ability of the receptor pool to accept electrons on the PSII electron acceptor side and improved the sta-bility of thylakoid membranes under NaCl stress. Therefore, increasing nitrogen applications under NaCl stress can promote poplar growth by improving the effi-ciency of light energy utilization.

Effects of Application of Nitrogen, Potassium and Glycinebetaine on Alleviation of Water Stress to Summer Maize

A pot experiment was conducted under water deficit and adequate water-supplied conditions with two maize genetypic varieties （Shaandan 9 and Shaandan 911） to study the effects of nitrogen, potassium and glycinebetaine （GlyBet） on the dry matter and grain yields as well as water use efficiency （WUE）. Determinations were made at different stages of the two varieties for revealing the function of these factors in increasing plant resistance to drought. Results showed that under a water-stressed condition, dry matter and grain yield were significantly reduced. However, the response of the two varieties to water stress was different： Shaandan 9 was significantly higher in dry matter and grain yields, and therefore could be regarded as a drought-resistant variety compared to Shaandan 911.Application of nitrogen, potassium and glycinebetaine raised dry matter and grain yield to different levels, and thereby alleviated the water stress and increased water use efficiency. These effects were higher for Shaandan 911 than for Shaandan 9. Under water-stressed conditions application of N fertilizer, either at low rate or at high rate, significantly increased dry matter, grain yield and water use efficiency. A significant different effect was found for Shaandan 911 between N rates, but not so for Shaandan 9. However, with supplemental water supply, effects of N fertilization were obviously decreased, showing that in addition to supplying nutrient, N fertilizer has a function in increasing drought-resistance of the crop. Potassium and glycinebetaine exhibited a remarkable function in increasing dry matter and grain yields as well as water use efficiency under water stress while such effects were obviously declined, even vanished, with supplemental water supply, indicating the important contribution of these factors in rise of drought-resistance ability of a crop.

翘嘴鲌及翘嘴鲌“全雌1号”氨氮胁迫下的生理应答反应及耐受性分析

【目的】探究翘嘴鲌及翘嘴鲌“全雌1号”在氨氮胁迫下的生理应答反应及耐受性,为新品种选育和健康养殖提供依据。【方法】采用实验生态学方法,在预试验确定96 h氨氮半致死浓度(96 h LC_(50))的基础上,研究不同浓度(0、8、16 mg/L)氨氮对翘嘴鲌及翘嘴鲌“全雌1号”存活指标、肝脏组织学、抗氧化酶活性的影响。【结果】(1)翘嘴鲌及翘嘴鲌“全雌1号”的死亡率随氨氮浓度与胁迫时间的增加而升高,在8和16 mg/L浓度下,翘嘴鲌“全雌1号”的死亡率更低;(2)组织学观察显示,随着氨氮浓度与胁迫时间的增加,肝血窦逐渐增大,局部破损增加,出现肝细胞融合,细胞轮廓与空泡界限模糊的现象增多。低浓度胁迫96 h与高浓度胁迫48 h和96 h均造成肝脏出现较大的病理学组织损伤。(3)SOD活性检测显示,对照组SOD活性稳定,而高、低浓度组则均呈先升高后降低再升高的趋势,且高浓度组高于低浓度组。同时,翘嘴鲌“全雌1号”增幅更大,降幅更小,其在相同氨氮浓度与胁迫时间下SOD活性较翘嘴鲌高。【结论】翘嘴鲌“全雌1号”较普通翘嘴鲌具有更强的氨氮抗逆性。

氨氮胁迫对翘嘴鳜幼鱼抗氧化酶、消化酶活性及应激相关基因表达的影响

为了解氨氮胁迫下翘嘴鳜(Siniperca chuatsi)幼鱼肝脏、胃抗氧化系统和消化系统的响应机制,以体质量为(15.27±0.67)g的翘嘴鳜幼鱼为研究对象,探讨了6个氨氮胁迫质量浓度(0、10、20、30、40、50 mg/L)下肝脏和胃中谷胱甘肽(GSH)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、脂质过氧化物(LPO)、胃蛋白酶(pepsin)、胃淀粉酶(AMS)、胃脂肪酶(LPS)的活性和IL-1β、IL-8、TNF-α、HSP90α等应激相关基因的表达情况。试验结果表明,随着氨氮质量浓度的提高,肝脏抗氧化相关酶中的SOD、CAT、GSH活性呈先升高后下降的趋势,LPO活性呈逐渐升高的趋势,IL-1β、HSP90α基因表达量呈先升高后降低的趋势,TNF-α表达量呈逐渐升高的趋势,IL-8表达量呈降低-升高-降低的趋势;胃消化酶中的胃蛋白酶活性呈现先升高后降低的趋势,而AMS和LPS活性呈逐渐升高的趋势。结果表明,在低浓度氨氮胁迫条件下,鱼体通过诱导抗氧化酶活性升高和应激相关基因表达上调来应对氧化应激损伤,同时诱导升高胃消化酶活性为机体提供能量,而高浓度氨氮胁迫则抑制了抗氧化酶活性和HSP90α基因的表达。

基于RNA-Seq筛选高粱低氮胁迫相关候选基因

研究低氮胁迫条件下不同高粱材料间的基因差异表达,为耐低氮型高粱品种选育和耐低氮胁迫的分子机制探究提供参考。选取2个耐低氮型高粱(BSX44和BTx378)为试验材料,设置正常和低氮胁迫2个处理,利用RNA-Seq技术对高粱苗期、抽穗期和开花期的基因表达进行分析,通过生物信息学对差异基因的生物学功能和代谢途径进行研究,筛选可能参与低氮调控的基因,了解氮高效基因型在氮素吸收利用过程中可能的分子途径。结果表明,在正常和低氮胁迫下,BTx378和BSX44在苗期分别筛选出937个和787个差异表达基因,抽穗期分别筛选出1305个和935个差异表达基因,开花期分别筛选出1402个和963个差异表达基因。对3个时期的差异表达基因进行鉴定,发现在苗期、抽穗期和开花期分别有246、371和306个基因在2个耐低氮高粱品种中共同差异表达,有28个基因在2个耐低氮品种的不同生育时期均差异表达,其中有5个基因上调表达,23个基因下调表达;对共同差异表达基因的KEGG相关代谢通路富集分析,发现主要集中在氮代谢、丙氨酸,天冬氨酸和谷氨酸代谢、甘油磷脂代谢、氨基酸的生物合成等途径,表明耐低氮型高粱可能通过这些途径相关基因的表达影响其对低氮胁迫的耐受性。

NaCl胁迫下pH值和氮素形态对狗牙根生长及钠钾离子调控的影响

以狗牙根〔Cynodon dactylon(Linn.)Pers.〕品种‘阳江’(‘Yangjiang’)为实验材料、2-(N-吗啡啉)乙磺酸(MES)为pH缓冲剂,采用水培法研究NaCl胁迫下pH值和氮素形态(铵态氮和硝态氮)对狗牙根生长和钠钾离子调控的影响。结果表明:处理1周后,若不添加MES,铵态氮处理组培养液的pH值下降到pH 4.0左右,而硝态氮处理组培养液的pH值则上升到pH 9.0左右;添加20 mmol·L^(-1)MES的铵态氮处理组培养液的pH值也下降到pH 4.0左右,而硝态氮处理组培养液的pH值则接近pH 7.0。与0 mmol·L^(-1)NaCl处理组相比,300 mmol·L^(-1)NaCl处理组狗牙根的枝条长度和枝条干质量显著(P<0.05)下降,而根长度、根干质量、根和叶中Na^(+)含量和Na^(+)/K^(+)比、钠钾选择性转运系数、叶Na^(+)和K^(+)的分泌量及分泌物Na^(+)/K^(+)比总体上显著升高。300 mmol·L^(-1)NaCl胁迫下,硝态氮处理组狗牙根的枝条长度、根长度、根干质量、根冠比、根中Na^(+)含量总体上显著高于铵态氮处理组,而叶中Na^(+)和K^(+)含量及Na^(+)/K^(+)比、叶Na^(+)和K^(+)的分泌量明显低于铵态氮处理组。300 mmol·L^(-1)NaCl胁迫下,20 mmol·L^(-1)MES处理组狗牙根的多数生长指标显著高于0 mmol·L^(-1)MES处理组,而根和叶中Na^(+)和K^(+)含量及Na^(+)/K^(+)比、钠钾选择性转运系数在0和20 mmol·L^(-1)MES处理组间的差异不显著。三因素方差分析结果表明:3个因子的单一和交互作用对多数生长指标、叶中Na^(+)含量和泌盐量相关指标的影响具有统计学意义。研究结果显示:硝态氮能缓解NaCl胁迫对狗牙根的伤害,而用MES缓冲根际酸碱环境对NaCl胁迫下狗牙根生长有一定的促进作用,因此,施用硝态氮或添加MES均有利于提高狗牙根的抗盐性。

硝化应激在肺动脉高压中的研究进展

肺动脉高压(pulmonary hypertension,PH)是一种进行性发展的肺血管疾病,病理基础包括内皮功能障碍、平滑肌细胞异常增生、炎症浸润以及肺纤维化。PH的发生机制尚不完全清楚,但硝化应激已经证实在PH中发挥了重要作用。该文综述了活性氮(reactive nitrogen species,RNS)的种类及肺循环中RNS的来源,以及由此引发的硝化应激在PH发生发展中的作用,以期为靶向抗硝化治疗的临床应用提供参考依据。

皖豫高效抗逆大豆根瘤菌Y2-4的选育

为筛选适合安徽、河南两地的大豆高效抗逆根瘤菌,从安徽和河南两地选取7个采样点采集大豆根瘤并分离根瘤菌,通过系统发育分子鉴定、回接大豆筛选、抗逆境胁迫能力测定筛选高效抗逆大豆根瘤菌,并通过初步田间接种试验对其促生效果进行了评估。结果显示:共分离得到621株大豆根瘤细菌,其中Sinorhizobium属菌株418株(67.3%),是该地区的优势大豆根瘤菌,Bradyrhizobium属菌株198株(31.9%),Rhizobium属菌株5株(0.8%,回接大豆不能结瘤)。筛选得到1株具有应用潜力的高效抗逆根瘤菌S.fredii Y2-4,与参比菌株CCBAU 45436相比,Y2-4菌株接种的大豆叶绿素含量、根瘤数、地上干重分别提高了1.8%、15.5%和9.8%,且在3%NaCl盐胁迫及38℃高温胁迫条件下仍具有生长能力。田间接种试验结果显示,在全氮(225 kg·hm^(-2)复合肥,氮磷钾比例15∶15∶15)、减氮26.6%(225 kg·hm^(-2)复合肥,氮磷钾比例11∶15∶15)、不施氮(225 kg·hm^(-2)复合肥,氮磷钾比例0∶15∶15)3种氮肥水平下接种Y2-4菌株均可以提高大豆产量,“减氮26.6%+接种Y2-4”处理较“全氮+不接种”处理条件下,大豆产量增加了25.5%。综上所述,Y2-4菌株可以作为皖豫两省部分地区的大豆高效抗逆根瘤菌接种菌株进行推广应用。

氨氮短期胁迫与恢复对克氏原螯虾的影响

为探究氨氮胁迫与恢复对克氏原螯虾抗氧化和免疫酶活性及组织结构的影响,将体质量(6.33±0.73)g的克氏原螯虾暴露于0、20、40、60、80 mg/L 5个氨氮质量浓度下,比较胁迫48 h时及恢复48 h后,各组肝胰腺、鳃和血清的抗氧化和免疫酶活性以及各组肝胰腺和肌肉组织结构的变化。试验结果显示:氨氮对克氏原螯虾幼虾24、48、72、96 h的半致死质量浓度分别为359.37、238.09、196.34、162.00 mg/L,安全质量浓度为16.20 mg/L。胁迫48 h后,除20 mg/L试验组外,其余试验组肝胰腺的总超氧化物歧化酶活性较对照组显著增强,80 mg/L组鳃的总抗氧化能力显著降低、过氧化氢酶活性显著增强,80 mg/L组血清的总超氧化物歧化酶活性显著增强;恢复48 h后,60 mg/L组肝胰腺和鳃的丙二醛含量较对照组显著上升,80 mg/L组鳃的过氧化氢酶活性较对照组显著增强,60 mg/L组血清的总抗氧化能力较对照组显著上升,其他试验组酶活性均恢复至对照组水平。氨氮胁迫48 h,随着氨氮质量浓度的升高,肝胰腺管腔逐渐变形、转运泡增大,鳃的呼吸上皮细胞开始脱落、微血管腔受损;恢复48 h后,肝胰腺的组织结构基本恢复正常,40、60、80 mg/L组鳃局部呼吸上皮细胞脱落,微血管腔受损。试验结果表明,20 mg/L质量浓度的氨氮胁迫48 h即会对克氏原螯虾抗氧化和免疫酶及组织结构造成损伤,解除胁迫48 h后可得到修复。克氏原螯虾经40、60、80 mg/L质量浓度的氨氮胁迫48 h后恢复48 h,鳃仍处于应激状态。