镧离子对苜蓿种子萌发活力、吸水量和膜透性的影响

20～700μg/ml的La(NO3)3处理的苜蓿种子吸水速率明显加快,膜的通透性增大,呼吸作用增强.其中,用500μg/ml La(NO3)3处理效果最佳,用1200～1500μg/ml La(NO3)3处理则抑制种子萌发.     

温度和湿度对伴性赤蚁sch系统致死性的影响

为进一步探讨家蚕伴性赤蚁(sch)致死的机理,比较了不同温度、湿度催青条件下,sch系统及其杂交F_1代和对照种黑蚁系统的孵化率、失水率、含水率、失水临界温度等。结果表明:伴性赤蚁sch系统在已_3至已_4期对温湿度敏感,受到高温和干燥的冲击,将获得“孵化不能”性状;温度、湿度因子对赤蚁sch孵化抑制均有较大的独立作用,sch表现出一定的“温度敏感性”和“湿度敏感性”;温度、湿度都能通过影响胚胎体内水分平衡失调而引起这种孵化不能;在不引起水分变化的情况下,温度还存在一条独立的抑制赤蚁孵化的途径。     

Microphytic crusts,shrub patches and water harvesting in the Negev Desert: the Shikim system

Human-made contour banks are a central component of theShikim water harvesting system in Israels Negev Desert.Efficient water capture depends on the presence of a stable microphytic crustwhich directs surplus surface runoff into the banks where it is stored. We usedsimulated rainfall to examine the impact of soil surface disturbance on runoffand sediment transport, and the effect of this on the efficiency of resourcecapture within the Shikim system. Two disturbance regimes:1) removal of the microphytic crust only, and 2) removal of the crust and shrubpatches by cultivation, were compared with an undisturbed control. In theundisturbed state, 32% of rainfall was redistributed as runoff. This runoffpenetrated approximately 27% deeper under the shrub patches compared with themicrophytic crust. When the microphytic crust was destroyed by simulatedtrampling, the runoff coefficient declined to 13%, and there was no significantdifference in water penetration between shrub and crust patches. Completedestruction of the shrub hummocks and crust by cultivation resulted in adeclinein the runoff coefficient to 6%. The result of sustained disturbance in thesepatchy Negev shrublands is a breakdown in spatial heterogeneity, a loss ofecosystem function, a reduction in ecosystem goods and services such as plantdiversity and production, and ultimately a reduction in pastoral productivity.These results reinforce the view that microphytic crusts are critical for theefficient operation of the Shikim water harvesting system.Given that practices such as cultivation and trampling which disturbmicrophyticcrusts result in enhanced infiltration, crusts should be left intact tomaximisethe water harvesting efficiency in these desert landscapes.This revised version was published online in May 2005 with corrections to the Cover Date.     

抗旱性不同的苹果属植物水分胁迫下核酸代谢及自由基变化

 水分胁迫引起苹果属植物中抗旱性较弱的平邑甜茶和抗旱性较强的新疆野苹果幼苗叶片相对含水量(RWC) 、DNA、RNA 含量下降, O₂^-·、H₂O₂ 含量增高, DNase、RNase 活性上升; 其中DNA 含量下降的幅度小于RNA , DNase 活性上升的幅度小于RNase。抗旱性较强的新疆野苹果在水分胁迫下幼苗叶片的RWC、DNA、RNA 含量下降的幅度以及O₂^-·、H₂O₂含量增高、DNase、RNase 活性上升的幅度均小于抗旱性较弱的平邑甜茶。水分胁迫下平邑甜茶和新疆野苹果幼苗叶片的DNA、RNA 含量与RWC、O₂^-·、H₂O₂ 含量和DNase、RNase 活性间均呈显著相关。     

黄皮种子脱水敏感性与核酸、蛋白质代谢的关系

黄皮种子发育晚期,胚内核酸和蛋白质合成能力增强,而花生种子发育晚期则呈下降趋势。脱水处理使生理成熟期黄皮胚核酸和蛋白质合成能力急剧下降,核酸水解酶活性增强。生物大分子代谢能力的变化是黄皮种子脱水敏感性的分子基础。     

Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter

Five successive batches of fattening pigs were raised, each during a four month period, on a totally concrete slatted floor in one experimental room and on straw based deep litter in another. The rooms were automatically ventilated to maintain a constant ambient temperature. Available floor space was of 0.75 m² per pig kept on the slatted floor and 1.20 m² per pig kept on the deep litter. With this last system, about 46 kg of straw were supplied per pig throughout a fattening period. The slurry pit was emptied and the litter removed after each batch. Once a month, the emissions of ammonia (NH₃), nitrous oxide (N₂O), methane (CH₄), carbon dioxide (CO₂), and water vapour (H₂O) were measured continuously for 6 consecutive days by infra-red photoacoustic detection.The performance of the animals was not significantly different according to the floor type.Gaseous emissions from pigs raised on the slatted floor and on the deep litter were, respectively, 6.2 and 13.1 g per pig per day for NH₃, 0.54 and 1.11 g per pig per day for N₂O, 16.3 and 16.0 g per pig per day for CH₄, 1.74 and 1.97 kg per pig per day for CO₂ and 2.48 and 3.70 kg per pig per day for H₂O. Except for the CH₄ emissions, all the differences were significant (P < 0.001). Thus, pig fattening on deep litter releases nearly 20% more greenhouse gases than on slatted floor, with 2.64 and 2.24 kg of CO₂-equivalents, respectively (P < 0.001). Whatever the floor type, emissions increased from the beginning to the end of the fattening periods by about 5 times for NH₃, 4 times for N₂O, 3 times for CH₄ and 2 times for CO₂ and H₂O. Correlation coefficients between CO₂-emissions and H₂O, NH₃ and CH₄ emissions were, on average for both floor types, 0.82, 0.77 and 0.74, respectively.Although rearing pigs on straw generally has a good brand image for the consumer, this rearing system produces more pollutant gases than keeping pigs on slatted floors.     

Effects of species and sex on plasma hormone and metabolite concentrations in crossbred Brahman cattle and crossbred water buffalo

Buffalo meat is tasty and indistinguishable from beef, and has been described as being lean and low in cholesterol in comparison with beef. However, little is known about the plasma hormone and metabolic profiles related to fat metabolism in buffalo, and how their levels are affected by species and sex. In this study levels of plasma hormones and metabolites were compared between species and sexes. Ten growing crossbred Brahman cattle and ten growing crossbred buffaloes (five males and five females in each), with an average age of 22 months were used. The animals were fed on an experimental diet composed of corn silage, brewer's spent grain and a concentrate mixture at a 50:30:20 ratio on a dry matter basis during a fattening period of 6 months. Blood samples were collected every month during the experiment, and were analysed for plasma leptin, insulin, glucose, triglyceride (TG) and total cholesterol (TC) concentrations. Plasma leptin, insulin and TC concentrations increased during fattening and were significantly (P < 0.05) higher in cattle than in buffaloes. These concentrations in cattle showed a big difference between sexes in comparison with buffaloes, and were higher in females than in males. The plasma glucose and TG concentrations did not differ (P > 0.05) between cattle and buffaloes.

The crude fat content of longissimus muscle was significantly higher in cattle than in buffalo. Differences in body fat deposition seem to have an influence on plasma leptin, insulin and TC concentrations differently between cattle and buffaloes.     

洮儿河沿岸地区水利工程建设的生态水文影响初探

水利工程建设在获得社会经济利用的同时也对生态水文问题造成明显的负面影响,在干旱半干旱地区此类问题尤为显著。本文分别探讨了洮儿河沿岸地区三类水利工程即水库、防洪堤和灌渠对于流域生态水文的影响,主要体现在:(1)减少水库下游河流径流量,加重下游水资源短缺问题;严重影响下游沼泽湿地水文,导致湿地退化(2)灌渠建设使地下水位抬升,加重土壤次生盐渍化问题;(3)防洪堤修建改变湿地水质,增大其矿化度和碱度。     

Isolation and Identification of a Variant Porcine Epidemic Diarrhea Virus and the Immune Efficacy of Its Inactivated Vaccine

This study was aimed to isolate a mutant strain of porcine epidemic diarrhea virus and prepare a PEDV inactivated vaccine with high valence by suspension culture process for immunizing against PEDV effectively in China.200 small intestines and theirs contents of diarrhea piglets died of diarrhea,collected from many large-scale pig farms in China,were detected by RT-PCR and sequenced,a mutant strain of porcine epidemic diarrhea virus was selected and put on the suspension-cultured Vero cells in a 2 L reactor for virus isolation and continuous cell culture,the harvested virus suspension,which was identified and determined TCID₅₀,was inactivated by formaldehyde and mixed with aluminum hydroxide gel adjuvant to prepare PEDV inactivated vaccine.After its physical behavior,stability viscosity,sterility test were checked out,the safety and immune efficacy were studied by immunizing the pregnant pigs and theirs piglets.The results were as follows:86 samples were detected positive in 200 samples,cytopathy occurred after the mutant strain samples screened were passaged to 5th generation,the virus suspension was harvested in 10th generation and identified as a mutant strain of PEDV,named PEDV-GF10 strain.The virus titer of harvested virus suspension was measured up to 1×10^8.0 TCID₅₀/mL after concentrated.After the vaccine was checked out,the sows,40 and 25 days before delivery in experimental groups,were injected into Xuehai acupoint with 4 mL vaccine and the pigs in blank group were free of immunifications.The results showed that there were no obvious differences in the production status of the sows in experimental groups and blank group and the temperature of theirs 3-day-old healthy piglets injected different doses of vaccine,and the vaccine was safe to the sows and piglets.Forty 3-day-old piglets producted by pregnant sows in experimental groups and blank group were randomly selected and taken 4 mL 1×10^8.0TCID₅₀/mL F10 virus culture.The PEDV morbidity of piglets in blank group was 100% after injection and the antibodies were negative;10% piglets in blank group had mild diarrhea symptoms,the protection rate was up to 90%,antibody of passive immunity in piglets lasted for more than 35 days.Virus titer of mutant strain of PEDV-GF10 improved a lot by suspension cell culture,the PEDV-GF10 inactivated vaccine was safe,and could effectively prevent and control the variation strain of PEDV in China.     

草坪草抗旱生理与节水技术研究进展

针对当前绿地草坪建设中水资源不足问题，分别论述了干旱胁迫对草坪草生长发育的影响及草坪草抵抗干旱的生理机制。并从节水灌溉、节水抗旱型品种选育、抗旱保水剂和草坪管理措施等方面综述了近年来在草坪业上的相关节水技术。