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81.
Effects of pretreatment of soil samples on N mineralization in incubation experiments 总被引:4,自引:0,他引:4
Summary We studied the effects of pretreating soil samples (field-fresh, drying at 40° and 105°C, freezing/thawing) on N mineralization in an incubation experiment and on the dynamics of the organic N fraction extracted by K2SO4 solution. The soil samples were collected from plots in a long-term field experiment with the application of mineral fertilizer and farmyard manure. Compared with the field-fresh soil samples, freezing/thawing resulted in higher NO
3
–
-N contents while the NH
4
+
-N and the organic N content were increased by drying at 105°C. During the incubation period N mineralization was highest after the samples were dried at 105°C and a little lower in those dried at 40°C. After freezing/thawing the order of magnitude of N mineralization remained the same. The difference in organic N between the beginning and the end of the incubation experiment and the mineral N content at the end of the experiment were correlated significantly. Despite this correlation, however, the change in the organic N content underestimated the N mineralization rates. 相似文献
82.
Nitrous oxide emissions as influenced by amendment of plant residues with different C:N ratios 总被引:1,自引:0,他引:1
To investigate the influence of plant residues decomposition on N2O emission, laboratory incubations were carried out for a period of 21 days using urea and five plant residues with a wide range of C:N ratios from 8 to 118. Incorporation of plant residues enhanced N2O and CO2 emissions. The two gas fluxes were significantly correlated (R2=0.775, p<0.001). Cumulative emissions of N2O and CO2 were negatively correlated with the C:N ratio in plant residues (R2=0.783 and 0.986 for N2O, and 0.854 for CO2, respectively). A negative relationship between the N2O-N/NO3−-N ratio and the C:N ratio was observed (R2=0.867) when residue plus urea was added. We calculated the changes in dissolved organic C (DOC) and the relevant changes in N2O emission. The incorporation of residues increased DOC when compared with the control, while the incorporation of residue plus urea decreased DOC. Cumulative emissions of N2O and CO2 were positively correlated with DOC concentration measured at the end of the incubation. In addition, the N2O emission fraction, defined as N2O-N emissions per unit N input, was not found to be a constant for either residue-N or urea-N amendment but dependent on C:N ratio when plant residue was incorporated. 相似文献
83.
在代用蛋壳中孵化鸡胚 总被引:19,自引:3,他引:16
本实验将正常孵化72h的鸡胚转移到代用蛋壳内培养。鸡胚的存活率在第10d和第18d时分别是100%和90%(23/25)。孵化率为52%(13/25)。 相似文献
84.
家蚕二化性品种(品系)转基因用蚕卵的预处理技术研究 总被引:3,自引:1,他引:2
家蚕为卵滞育昆虫,二化性家蚕品种(品系)的化性由上代卵期温度与光照等调控。将若干个二化性家蚕品种(品系)以17~18℃温度催青诱导子代蚕卵非滞育,筛选出1个经济性状较优的实用品种"秋丰"、1个突变品系P33,二者非滞育卵圈比例分别达到96.4%和89.6%,正常催青的良卵实用孵化率分别达到96.11%和98.58%,解决了采用显微注射法以家蚕实用品种构建转基因系统过程中因蚕卵滞育不能及时孵化的难题。另对利用20%盐酸-2%甲醛混合液刺激解除蚕卵滞育的方法以及非滞育蚕卵表面用70%乙醇消毒的方法进行了尝试,前者可以获得96%以上的孵化率,后者可以缩短蚕卵预处理时间。 相似文献
85.
Response of soil organic matter dynamics to conversion from tropical forest to grassland as determined by long-term incubation 总被引:1,自引:0,他引:1
Understanding soil organic carbon (SOC) responses to land-use changes requires knowledge of the sizes and mean residence times
(MRT) of specific identifiable SOC pools over a range of decomposability. We examined pool sizes and kinetics of active and
slow pool carbon (C) for tropical forest and grassland ecosystems on Barro Colorado Island, Panama, using long-term incubations
(180 days) of soil and stable C isotopes. Chemical fractionation (acid hydrolysis) was applied to assess the magnitude of
non-hydrolysable pool C (NHC). Incubation revealed that both grassland and forest soil contained a small proportion of active
pool C (<1%), with MRT of ~6 days. Forest and grassland soil apparently did not differ considerably with respect to their
labile pool substrate quality. The MRT of slow pool C in the upper soil layer (0–10 cm) did not differ between forest and
grassland, and was approximately 15 years. In contrast, changes in vegetation cover resulted in significantly shorter MRT
of slow pool C under grassland (29 years) as compared to forest (53 years) in the subsoil (30–40 cm). The faster slow pool
turnover rate is probably associated with a loss of 30% total C in grassland subsoil compared to the forest. The NHC expressed
as a percentage of total C varied between 54% and 64% in the surface soil and decreased with depth to ~30%. Grassland NHC
had considerably longer MRTs (120 to 320 years) as compared to slow pool C. However, the functional significance of the NHC
pool is not clear, indicating that this approach must be applied cautiously.
An erratum to this article can be found at 相似文献
86.
87.
[目的]以染料木素(Gen)、葡萄糖醛酸内酯(Glu)处理的鼠肝微粒体为体外代谢模型,考察不同条件下尿苷二磷酸葡萄糖醛酸转移酶(UGTs)的活性及其对扑热息痛(APAP)代谢的影响。[方法]采用染料木素、葡萄糖醛酸内酯以及2种药物联合对小鼠进行体内诱导,取诱导后小鼠肝脏制备微粒体,构建微粒体体外孵育模型,以4-硝基酚(4-NP)为底物检测UGTs活性,加APAP到孵育体系中反应后再利用HPLC测定其含量。[结果]染料木素及2种药物联合诱导后的UGTs比活力分别为(0.553±0.039)和(0.696±0.046)U/mg,对照组和Glu组分别为(0.449±0.017)和(0.457±0.030)U/mg;在加入相同浓度APAP的情况下,Gen组APAP的剩余量低于空白组及Glu组。[结论]染料木素可以显著增强UGTs活性和提高APAP代谢效率。 相似文献
88.
外植体及培养条件对葡萄不定芽再生的影响 总被引:2,自引:0,他引:2
以优良无核葡萄品种莫利莎、皇家夏天为试材,分别从外植体类型、叶片接种部位、接种方式及培养条件等方面进行不定芽再生技术研究。结果表明,2品种葡萄试管苗离体叶片切割后接种较节间和叶柄容易诱导不定芽再生;将叶片切分为叶尖、叶中、叶基部叶块分别接种,其不定芽再生能力没有差异;取自培养30~50d继代苗上的叶片,其不定芽再生效果相同;叶块以近轴面或远轴面接触培养基的接种方式对不定芽再生影响不大,不过叶片远轴面贴近培养基接种,产生的愈伤组织状态较好;25℃左右小幅变温或恒温的条件能诱发2个葡萄品种产生较多的不定芽;葡萄不定芽再生须经黑暗培养或弱光培养,暗培养时间在2周与4周之间再生效果差异不显著。 相似文献
89.
90.