我国豆科植物属的地理分布型及其结瘤固氮性

本文对我国豆科植物属──主要指我国野生自产的属──的地理分布型进行了分析和总结，井阐述了豆科植物属在地理分布上的几个特性；区域局限性、间断性和扩散性。通过对属的大小类型与地理分布型的对比分析，发现热带成分属与属的大小类型关系密切。关于豆科植物的结瘤固氮特性，三个亚科是有区别的，这除了与遗传因素有关外，还与地理分布环境有一定关系。随着豆科植物在我国当今农业、林业及正在兴起并迅速发展的农林复合业（Ａｇｒｏ－ｆｏｒｅｓｔｒｙ）中重要性的增强，尤其对土壤改良和土地持续利用的贡献加大，本文对于在区域范围内选择豆科植物属种具有理论指导意义。

3种来源兼性纤维素分解菌与固氮菌混合对体外发酵的影响

本试验选取分离自瘤胃液、土壤、饲料中的3株高酶活性的兼性厌氧纤维素分解菌(L6、T1、S4)和3株低酶活性的兼性厌氧纤维素分解菌(L4、T4、S1),分别与自瘤胃内取提的1种兼性厌氧固氮菌(C5)以4:1混合,形成6种混合菌(记为L6、T1、S4、L4、T4、S1),通过体外培养试验来探讨其对体外发酵的影响。试验设置6个试验组和1个对照组,每组7个重复。向每个注射器内装入200 mg发酵底物(精:粗=45:55),与1 m L的混合菌液(对照组加入1 m L灭活的菌液)将培养液加至30 m L,进行体外发酵试验。发酵时间为24 h,分别记录2、4、8、12、24h的产气量,测定发酵指标。结果表明:与对照组相比,试验组对产气量、pH、氨态氮(NH_3-N)、菌体蛋白(MCP)、挥发性脂肪酸(VFA)及滤纸纤维素酶活性均有显著影响(P<0.05),其中L4试验组对VFA、NH_3-N及滤纸纤维素酶活等影响效果最好;与高酶活试验组相比,低酶活试验组对产气量、pH、VFA浓度及NH_3-N浓度有显著影响(P<0.05),对MCP浓度和滤纸纤维素酶活性没有显著影响(P>0.05)。由此可见,添加的混合菌对体外发酵有明显促进作用,其中L4试验组对体外发酵的影响效果最好;低酶活性的兼性纤维素分解菌对体外发酵的促进作用比高酶活性的兼性纤维素分解菌好。

公农5号紫花苜蓿与根瘤菌共生匹配组合的筛选

为了研究紫花苜蓿与不同品种根瘤菌之间的共生匹配性,获得高效根瘤菌用于接种,试验在吉林省大安地区、农安地区和黑龙江地区采集15株苜蓿根瘤菌与公农5号紫花苜蓿进行共生匹配,分别在土壤盆栽及大田试验条件下,测定15株苜蓿根瘤菌与公农5号的各生长效应指标,并进行了固氮性分析。结果表明:HLCC3002菌株与公农5号能很好地共生匹配,从而确定HLCC3002菌株为与公农5号紫花苜蓿相匹配的高效根瘤菌。

Purification and Characteristics of Mn-containing Nitrogenase Component Ⅰ

A mutant UW 3, which is unable to fix N 2 in the presence of Mo (Nif -) but undergo phenotypic reversal to Nif + under Mo deficiency, was able to grow in Mo- and NH 3-deficient medium containing Mn, and the growth was accelerated by Mn at low concentration. A partly purified nitrogenase component Ⅰ protein separated from UW 3 grown in the Mn-containing medium was shown to contain Fe and Mn atoms (ratio of Fe/Mo/Mn: 10.41/0.19/1.00) with C 2H 2- and H +-reducing activity which almost equal to half of that of MoFe protein purified from wild-type mutant of Azotobacter vinelandii Lipmann. This protein was obviously different from MoFe protein in both absorption spectrum and circular dichroism, and the molecular weight of subunits in Mn-containing protein was close to that of α subunit in MoFe protein. The preliminary results indicated that the protein containing Mn might be a nitrogenase component Ⅰ protein.

Science Letters:Alterations in seedling vigour and antioxidant enzyme activities in Catharanthus roseus under seed priming with native diazotrophs

An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters. There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximum of 50% germination, whereas Azospirillum and Azotobacter were on par with C. roseus with respect to their vigour index. There was significant difference in the population of total diazotrophs. Azospirillum and Azotobacter between rhizosphere and non-rhizosphere soils of C. roseus had the same trend and were observed at various locations of the study. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased to a significant extent due to the treatment with diazotrophs.

Effect of nitrogen on microstructure and mechanical properties of Cr Mn Fe VTi6 high entropy alloy

In order to evaluate interstitial strengthening effect on the properties of high entropy alloy(HEA),a nitrogen-doped Cr Mn Fe VTi6 HEA was fabricated by mechanical alloying(MA)and spark plasma sintering(SPS).XRD,SEM,TEM and FIB were used to characterize the phase composition and microstructure of this material.The sintered bulk HEA exhibits a microstructure comprising TiNx,BCC,Laves and B2 phases.The HEA exhibits high yield strength(>2729 MPa)and hardness in lower temperature range of<380℃.Quantitative calculations of the contributions from each strengthening mechanism in the BCC phase indicate that the interstitial strengthening by nitrogen is the dominant mechanism.Nitrogen additions in the BCC phase can produce a yield strength increase of-634 MPa/at.%,which is much higher than the strengthening effects of carbon or boron additions in other alloys.This demonstrates that adding nitrogen is a viable approach for enhancing the strength of HEAs.

Application of nitrogen-fixing cyanobacteria in restoration of saline and alkaline soils of Songnen Plain in China

The salt-resistant nitrogen-fixing cyanobacteria 888 was experimentally applied to the reclamation of saline and alkali soil in Songnen Plain in China. The pH, electrical conductivity (EC) and sodium adsorption ratio (SAR) of different saline soils were studied and compared. Results show that different saline soils exhibit various physico-chemical properties. Saline-sodic soils in Songnen Plain are ameliorated by using nitrogen-fixing blue-green algae 888 in the experiment. It is indicated that cyanobacteria 888 can grow in saline and alkaline soils, and the conditions favorable for its growth are soil moisture of 50% and dry algae inoculation at 0.03 mg/cm2. The main actions of nitrogen-fixing cyanobacteria are keeping the adsorbability of rubber sheath for sodium, increasing the organic matter content of the soils and decreasing the pH and the degree of salinity in the soils. But the arid climate and soil depth are the main factors that limit the restoration of saline and alkaline soils.