排序方式： 共有42条查询结果，搜索用时 15 毫秒
1.
[目的]研究微波辅助碱提酸析法提取黎豆黑色素的工艺条件。[方法]分别采用碱提酸析法和微波辅助碱提酸析法提取成熟黎豆种皮中的黑色素,以紫外分光光度法测定黎豆黑色素的含量。[结果]黎豆种皮黑色素含量为2.41%;碱提酸析法最佳提取工艺为1.0mol/L NaOH溶液为提取剂、料液比1∶20(g/ml),浸提时间4～6 h,再调提取液pH值为2,进行酸析;在此条件下,黑色素粗提物得率为(91.2±2.0)%,黑色素纯度为(36.5±2.1)%;微波辅助碱提酸析最佳工艺为料液比1∶20(g/ml)、1.0 mol/L NaOH溶液为提取剂、微波高档功率处理25 min;在此条件下,黑色素粗提物得率为(95.3±1.5)%,黑色素纯度达到(37.4±1.5)%。[结论]黎豆种皮中含有较为丰富的植物黑色素,值得进一步研究和开发利用;微波辅助较常规碱提酸析工艺明显提高了黎豆种皮黑色素粗提物得率,且大大缩短了提取时间。 相似文献
2.
In the low-input rice–wheat production systems of Nepal, the N nutrition of both crops is largely based on the supply from soil pools. Declining yield trends call for management interventions aiming at the avoidance of native soil N losses. A field study was conducted at two sites in the lowland and the upper mid-hills of Nepal with contrasting temperature regimes and durations of the dry-to-wet season transition period between the harvest of wheat and the transplanting of lowland rice. Technical options included the return of the straw of the preceding wheat crop, the cultivation of short-cycled crops during the transition season, and combinations of both. Dynamics of soil Nmin, nitrate leaching, nitrous oxide emissions, and crop N uptake were studied throughout the year between 2004 and 2005 and partial N balances of the cropping systems were established. In the traditional system (bare fallow between wheat and rice) a large accumulation of soil nitrate N and its subsequent disappearance upon soil saturation occurred during the transition season. This nitrate loss was associated with nitrate leaching (6.3 and 12.8 kg ha−1 at the low and high altitude sites, respectively) and peaks of nitrous oxide emissions (120 and 480 mg m−2 h−1 at the low and high altitude sites, respectively). Incorporation of wheat straw at 3 Mg ha−1 and/or cultivation of a nitrate catch crop during the transition season significantly reduced the build up of soil nitrate and subsequent N losses at the low altitude site. At the high altitude site, cumulative grain yields increased from 2.35 Mg ha−1 with bare fallow during the transition season to 3.44 Mg ha−1 when wheat straw was incorporated. At the low altitude site, the cumulative yield significantly increased from 2.85 Mg ha−1 (bare fallow) to between 3.63 and 6.63 Mg ha−1, depending on the transition season option applied. Irrespective of the site and the land use option applied during the transition season, systems N balances remained largely negative, ranging from −37 to −84 kg N ha−1. We conclude that despite reduced N losses and increased grain yields the proposed options need to be complemented with additional N inputs to sustain long-term productivity. 相似文献
3.
Phosphorus deficiency and aluminium toxicity in weathered soils can be amended by applying organic residues. Nitrogen mineralization, changes in P-availability and changes in salt-extractable Al following the incorporation of residues of various green manures (Flemingia congesta, Mucuna pruriens, Pueraria phaseoloides, Tithonia diversifolia) were quantified in a field core incubation experiment. Dried residues were added at an application rate of 45 kg P ha−1 to two soils representative for the main soil groups of the South Vietnamese uplands, set up in incubation cores in an experimental field near Ho Chi Minh City, Vietnam.Decomposition of the residues proceeded at high rates. Mineralized nitrogen from the residues was recovered mainly as ammonium during the first 2 weeks of incubation. Nitrogen release from Tithonia residues with the highest lignin content and lignin:N ratio occurred more gradually compared to the three legumes. Resin-extractable P was significantly increased by residue treatments. Largest and sustained increases in resin-extractable P (0.67 and 2.06 mg P kg−1 in the two soils) were observed in samples amended with Tithonia, which was related to the large P-content (0.37%) and small C:P ratio (110) of the residues. The P-concentration in the residues, rather than the total amount of P applied through the residues, affected the increase in P-availability. The increase in resin-extractable P was correlated to the P-content (R=0.64) and C:P ratio (R=−0.65) of the residues. Salt-extractable Al-concentrations were considerably reduced by the organic amendments, up to 70 and 50% in the two soils. At the rate of 45 kg P ha−1, no significant differences between the residue treatments to reduce soil acidity were observed.As such, the application of high quality residues that are rich in P, in particular T. diversifolia, may enhance crop production by creating favourable soil conditions during the initial stages of plant development of the main crop. 相似文献
4.
A Okito 《Soil biology & biochemistry》2004,36(7):1179-1190
To quantify the contribution of biological nitrogen fixation (BNF) to legume crops using the 15N natural abundance technique, it is necessary to determine the 15N abundance of the N derived from BNF—the B value. In this study, we used a technique to determine B whereby both legume and non-N2-fixing reference plants were grown under the same conditions in two similar soils, one artificially labelled with 15N, and the other not. The proportion of N derived from BNF (%Ndfa) was determined from the plants grown in the 15N-labelled soil and it was assumed that the %Ndfa values of the legumes grown in the two soils were the same, hence the B value of the legumes could be calculated. The legumes used were velvet bean (Mucuna pruriens), sunnhemp (Crotalaria juncea), groundnut (Arachis hypogaea) and soybean (Glycine max) inoculated, or not, with different strains of rhizobium. The values of %Ndfa were all over 89%, and all the legumes grown in unlabelled soil showed negative δ15N values even though the plant-available N in this soil was found to be approximately +6.0‰. The B values for the shoot tissue (Bs) were calculated and ranged from approximately −1.4‰ for inoculated sunnhemp and groundnut to −2.4 and −4.5‰ for soybean inoculated with Bradyrhizobium japonicum strain CPAC 7 and Bradyrhizobium elkanii strain 29W, respectively. The B (Bwp) values for the whole plants including roots, nodules and the original seed N were still significantly different between the soybean plants inoculated with CPAC 7 (−1.33‰) and 29W (−2.25‰). In a parallel experiment conducted in monoxenic culture using the same soybean variety and Bradyrhizobium strains, the plants accumulated less N from BNF and the values were less negative, but still significantly different for soybean inoculated with the two different Bradyrhizobium strains. The results suggest that the technique utilized in this study to determine B with legume plants grown in soil in the open air, yields B values that are more appropriate for use under field conditions. 相似文献
5.
Assessment of the preference of sheep for fresh, dried or ensiled forms of mucuna (Mucuna pruriens var utilis) forage was followed by investigations into the effect of supplementing straw-based diets with the forage. Four sheep were offered fresh, dried and ensiled forms of the forage in a cafeteria style to assess their preference. In the second experiment, 20 sheep were randomly assigned to four dietary treatments, namely, alkali-treated straw only (M0), treated straw supplemented with mucuna forage at 0.3% (M10), 0.6% (M20) or 0.75% (M25) of body weight (approximately 10%, 20% and 25%, respectively, of the total dry matter intake). The daily feed intakes were determined and the sheep were weighed weekly for 10 weeks. The sheep showed a marked preference for fresh mucuna forage over either the dried or ensiled forms. The total dry matter intake increased by 15% and 21%, respectively, with M20 and M25. All the groups lost weight over the feeding period. However, only M0 gave weight losses during the second half of the feeding period. The feed conversion efficiency followed a trend similar to that for weight gains. M20 had the greatest effect on growth and feed conversion efficiency. 相似文献
6.
7.
[目的]筛选常春油麻藤(Mucuna sempervirens)最佳播种和扦插繁殖技术。[方法]采用磨破种皮和不同温度的热水浸泡种子处理,开展种子发芽试验;采用L9(34)正交试验设计研究插穗年龄、激素种类、激素浓度对常春油麻藤扦插的影响。[结果]种子不经任何处理,发芽率为28.3%,将种皮磨破后播种,种子发芽率为71.6%,明显高于种皮完好的种子发芽率;用热水浸泡种子可提高种子发芽率,但影响不明显;插穗年龄对扦插生根有显著影响,其中1~2年生枝条扦插成活率最高,其次为多年生枝条,当年生嫩枝成活率最低,激素种类和激素浓度对生根率的影响较小。[结论]磨破种皮可明显提高常春油麻藤种子的发芽率,A2B3C2为扦插处理试验最优组合,即1~2年生枝条用200 mg/L的IBA处理,扦插生根率最高。 相似文献
8.
猫豆是广西种植的一种特色药用植物,近年来发生一些重要病害,为明确这些病害种类,对广西猫豆主产区进行主要病害种类调查和病原鉴定。每块地采取5点取样法进行取样调查,并通过形态特征和rDNA ITS序列分析结果对病原菌进行鉴定。研究结果发现,猫豆上发生的主要病害有4种,分别为猫豆炭疽病（Colletotrichum gloeosporioides）、猫豆茎溃疡病（Phomopsis sp.）、猫豆斑枯病（Alternaria sp.）和猫豆褐斑病（Pseudocercospora sp.）,这些病害的发病率达30％~80％。 相似文献
9.
常春油麻藤、中华常春藤和扶芳藤的光合特性比较分析 总被引：2，自引：0，他引：2
采用LI-6400光合测定仪对盆栽的常春油麻藤(Mucuna sempervirens)、中华常春藤(Hedera nepalensis var.sinensi)和扶芳藤(Euonymus fortunei)进行光响应曲线、温度响应曲线和相对湿度响应曲线的测定。对比分析3种藤本植物的光补偿点(LCP)、光饱和点(LSP)、最大净光合速率(Pn)、最大表观量子效率(AQYmax)等光合特性指标,并研究分析光强、温度和相对湿度对3种藤本光合特性的影响。结果表明,常春油麻藤对有效光能辐射的利用范围最大,其次是扶芳藤,再次为中华常春藤,3种藤本植物的最适温度均在26~30℃,且对高湿环境条件的适应性均比较强。 相似文献
10.
Background : Rice production in low‐input systems of West Africa relies largely on nitrogen supply from the soil. Especially in the dry savanna agro‐ecological zone, soil organic N is mineralized during the transition period between the dry and the wet seasons. In addition, in the inland valley landscape, soil N that is mineralized on slopes may be translocated as nitrate into the lowlands. There, both in‐situ mineralized as well as the laterally translocated nitrate‐N will be exposed to anaerobic conditions and is thus prone to losses. Aim : We determined the dynamics of soil NO3‐N along a valley toposequence during the dry‐to‐wet season transition period and the effects of soil N‐conserving production strategies on the grain yield of rainfed lowland rice grown during the subsequent wet season. Methods : Field experiments in Dano (Burkina Faso) assessed during two consecutive years the temporal dynamics and spatial fluxes of soil nitrate along a toposequence. We applied sequential and depth‐stratified soil nitrate analysis and nitrate absorption in ion exchange resin capsules in lowlands that were open to subsurface interflow and in those where the interflow from the was intercepted. During one year only we also assessed the effect of pre‐rice vegetation on conserving this NO3‐N as well as on N addition by biological N2 fixation in legumes using δ15N isotope dilution. Finally, we determined the impact of soil N fluxes and their differential management during the transition season on growth, yield and N use of rainfed lowland rice. Results : Following the first rainfall event of the season, soil NO3‐N initially accumulated and subsequently decreased gradually in the soil of the valley slope. Much of this nitrate N was translocated by lateral sub‐surface flow into the valley bottom wetland. There, pre‐rice vegetation was able to absorb much of the in‐situ mineralized and the laterally‐translocated soil NO3‐N, reducing its accumulation in the soil from 40–43 kg N ha?1 under a bare fallow to 1–23 kg N ha?1 in soils covered by vegetation. Nitrogen accumulation in the biomass of the transition season crops ranged from 44 to 79 kg N ha?1 with a 36–39% contribution from biological N2 fixation in the case of legumes. Rice agronomic performance improved following the incorporation as green manure of this “nitrate catching” vegetation, with yields increasing up to 3.5 t ha?1 with N2‐fixing transition seasons crops. Conclusion : Thus, integrating transition season legumes during the pre‐rice cropping niche in the prevailing low‐input systems in inland valleys of the dry savanna zone of West Africa can temporarily conserve substantial amounts of soil NO3‐N. It can also add biologically‐fixed N, thus contributing to increase rice yields in the short‐term and, in the long‐term, possibly maintaining or improving soil fertility in the lowland. 相似文献