The acetylene-induced decline in nitrogenase activity in root nodules of Elaeagnus angustifolia

The rate of C₂H₂ reduction by nodulated seedlings of Elaeagnus angustifolia (Russian olive) was followed as a function of time. Our goals were to: 1) determine whether there is an C₂H₂-induced decline in nitrogenase activity; and 2) investigate the mechanism of any decline. We found a peak rate of C₂H₂ reduction at 1.5 min after the introduction of C₂H₂ that was followed by a rapid decline in activity to 56% of the peak value. After the decline there was a partial recovery to 67% of the peak value at 60 min. When the pO₂ was decreased during the decline there was no significant effect (p0.05) on nitrogenase activity. When the C₂H₂ reduction assay was preceded by an incubation in a gas mixture (20 kPa O₂) with Ar substituted for N₂, there was little decline in nitrogenase activity as a function of time, but the rate of C₂H₂ reduction per gram nodule was reduced by approximately 50%. From these results we conclude that t Elaeagnus angustifolia exhibits a pronounced C₂H₂-induced decline and consequently the initial peak rate C₂H₂ reduction must be determined to obtain a valid measure of nitrogenase activity. We further suggest that cessation of NH₃ formation initiates the decline and that the decline is not caused by a change in nodule permeability to gases.     

From endogenous to exogenous pattern formation: Invasive plant species changes the spatial distribution of a native ant

Invasive species are a significant threat to global biodiversity, but our understanding of how invasive species impact native communities across space and time remains limited. Based on observations in an old field in Southeast Michigan spanning 35 years, our study documents significant impacts of habitat change, likely driven by the invasion of the shrub, Elaeagnus umbellata, on the nest distribution patterns and population demographics of a native ant species, Formica obscuripes. Landcover change in aerial photographs indicates that E. umbellata expanded aggressively, transforming a large proportion of the original open field into dense shrubland. By comparing the ant's landcover preferences before and after the invasion, we demonstrate that this species experienced a significant unfavorable change in its foraging areas. We also find that shrub landcover significantly moderates aggression between nests, suggesting nests are more related where there is more E. umbellata. This may represent a shift in reproductive strategy from queen flights, reported in the past, to asexual nest budding. Our results suggest that E. umbellata may affect the spatial distribution of F. obscuripes by shifting the drivers of nest pattern formation from an endogenous process (queen flights), which led to a uniform pattern, to a process that is both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. The number and sizes of F. obscuripes nests in our study site are projected to decrease in the next 40 years, although further study of this population's colony structures is needed to understand the extent of this decrease. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.     

A Type-A chalcone isomerase mRNA is highly expressed in the root nodules ofElaeagnus umbellate

We have used the hybridization-competition method to isolateEuNOD-CHI from a root nodule cDNA library ofElaeagnus umbellate. This cDNA clone encodes chalcone isomerase (CHI) for a protein of 256 amino-acid residues and a mature molecular mass of 28 kDa. Multiple sequence alignment and phylogenetic analysis have demonstrated that EuNOD-CHI can be classified as Type I. Moreover, northern hybridization shows that theEuNOD-CHI gene is highly expressed in root nodules, with levels increasing during nodule development The highest level of expression is at 6 to 8 weeks after inoculation, decreasing thereafter. Genomic Southern hybridization also demonstrates thatEuNOD-CHI has as many as two copies in theE umbellate genome. Taken together with the previous results, we propose that the higher expression level of theEuNOD-CHI gene in root nodules is likely associated with this species’ defense mechanism against infection byFrankia.     

大孔吸附树脂提取分离翅果油树叶总黄酮的研究

通过吸附容量和洗脱效果的选择,从5种大孔吸附树脂中确定出LSA—10树脂最适于翅果油树叶中总黄酮的吸附和分离。研究了该树脂吸附翅果油树叶中总黄酮的最佳工艺条件,其结果为：(1)洗脱剂为50％～70％乙醇溶液;(2)上柱液pH=4时,此树脂对翅果油树叶中总黄酮的吸附容量最大;(3)吸附容量随着吸附时间的增加而升高,最佳吸附时间为8～10h;(4)随着上柱液浓度的增加,吸附容量也相应增加,而且浓度越大,这种差别越明显,但浓度不宜过高,以澄清为好。     

我国特有珍稀植物翅果油树濒危原因分析

翅果油树是我国特有种,为国家2级珍稀濒危保护植物,主要分布于山西南部的低山和丘陵区以及陕西秦岭北麓的户县。翅果油树分布区的生态环境特征是：热量充足,降水量较少,立地条件较差。翅果油树濒危的主要原因有（1）果实形态结构特殊,不利于传播和萌发,（2）果实结实率较低,（3）种子寿命短,发芽率低,（4）翅果油树幼苗缺乏竞争力和（5）人力破坏严重。此外,针对翅果油树的濒危现状和原因,还提出了科学保护对策。     

壳聚糖絮凝沉淀纯化翅果油树叶片多糖的方法探究

采用壳聚糖絮凝沉淀法对翅果油树(Elaeagnus mollis Diels)叶片多糖进行纯化研究,分别考察了壳聚糖用量、絮凝时间、絮凝温度及溶液酸碱度(pH)对吸附色素、沉降蛋白质和多糖损失率的影响,并采用正交试验优化出壳聚糖絮凝法纯化翅果油树叶片多糖的最佳条件为:壳聚糖用量1 mg/mL、溶液pH值=5、絮凝时间50~70 min、絮凝温度20~40℃。实验结果表明,在最佳条件下,色素含量和蛋白质含量分别降低了69%左右和35%左右,多糖的纯度也得到了一定的提高。     

山西翅果油树群落的多样性研究

用丰富度指数、多样性指数和均匀度指数对山西翅果油树群落的多样性进行了研究 ,并用相关分析研究了海拔与多样性指数及多样性指数间的关系 ,结果表明 :1 )在干扰强烈的生境中 ,翅果油树群落具有较低的丰富度指数、多样性指数的均匀性 ,而接近顶极群落阶段 ,多样性指数和丰富度指数也较低 ,但具有较高的均匀性 ;干扰强度较小的生境中 ,群落具有较高的丰富度指数、多样性指数和均匀性。2 )灌木层和草本层的丰富度、多样性指数和均匀度指数呈现多元化的趋势。 3)海拔对山西翅果油树群落多样性的影响不显著。     

Quercetin,Kaempferol and Isorhamnetin in Elaeagnus pungens Thunb. Leaf: Pharmacological Activities and Quantitative Determination Studies

Elaeagnus pungens leaf was documented to be very effective to treat asthma and chronic bronchitis both as traditional Chinese medicine and minority traditional medicine; yet the actual effective components still remain unknown. This work is to investigate the anti‐inflammatory, antalgic and antitussive activities of E. pungens leaf, quercetin and kaempferol, and their contents in E. pungens leaf. Pharmacological experiments showed that they could considerably reduce ear‐swelling of mouse and relieve writhing reaction of mouse; they could also prevent mouse from coughing significantly. These findings suggested that quercetin and kaempferol are major effective components treating asthma and chronic bronchitis. Quantitative analysis results indicated that the levels of quercetin, kaempferol and isorhamnetin varied greatly in different species of Elaeagnus and in different plant parts: E. pungens leaf is more similar to Elaeagnus umbellate leaf chemically; quercetin level is exceptionally high in Elaeagnus oldhami leaf; E. pungens leaf is a better medical part for treating asthma and chronic bronchitis in comparison with other parts.     

翅果油树茎段愈伤组织和芽发生的组织学研究

本文对翅果油树大宫灯型茎段培养在ＭＳ附加６－ＢＡ较高、ＮＡＡ较低浓度的培养基上培养０～３０ｄ的组织学变化进行了研究。创伤对其愈伤组织的形成有明显的刺激作用,培养３～４ｄ切口处的皮层细胞、形成层细胞、韧皮部薄壁细胞以及髓组织细胞,甚至表皮细胞均脱分化开始分裂;培养８～１１ｄ,切口明显膨大,起源于髓及维管组织周围薄壁细胞的愈伤组织突起大;培养１２～２０ｄ愈伤组织块中出现了分生组织和维管组织结节;培养２１～３０ｄ,愈伤组织表层和近表层细胞分化出芽原基,但与维管组织结节无直接联系。