蕨菜多酚氧化酶的酶学性质

研究了蕨菜[Pteridium aquilinum (L．) Kuhn var．latiusculum (Desv．) Underw．]多酚氧化酶的动力学性质,结果表明：以邻苯二酚为底物,该酶最适pH为7．4,最适温度为25℃,60℃以上使酶迅速失活,动力学方程v=619．08[S]/(0．031 [S]),Vc、异Vc钠、NaHSO3、L-Cys可完全抑制酶活性,饱和NaCl能显著抑制酶活性,蔗糖、SDS对酶有激活作用。该酶能催化邻苯二酚、焦性没食子酸氧化,但对焦性没食子酸亲和力更强。     

Herpetomonas roitmani (Fiorini et al., 1989) N. Comb.: A Trypanosomatid with a Bacterium-like Endosymbiont in the Cytoplasm

The trypanosomatid previously described as Crithidia roitmani is characterized here at the ultrastructural and biochemical levels. The data indicates that the parasite belongs to the Herpetomonas genus, and we therefore suggest the flagellate to be denominated as Herpetomonas roitmani n. comb. Cladistic analysis of isoenzyme data generated by eight different enzymes showed that the parasite presented a distinct banding pattern and could be grouped with some Herpetomonas spp., but not with Crithidia spp., used as reference strains. Accordingly, when the parasites were grown for longer periods in Roitman's defined medium, expontaneous differentiation from promastigotes to opisthomastigotes (typical of the Herpetomonas genus) occurred. Transmission electron microscopy revealed the presence of bacterium-like endosymbionts in the cytoplasm of all evolutive forms of the parasite. All morphological alterations characteristic of endosymbiont-bearing trypanosomatids could be observed.     

Effects of cyanogenesis in bracken fern (Pteridium aquilinum) on associated insects

Abstract. 1. The relationship between cyanogenesis in bracken fern and the insect fauna feeding on the plant was investigated over a 3 year period. The most common insects between May and July, while cyanide levels were high, were the sawflies Strongylogaster impressata Provancher, S.multicincta Norton, Aneug-menus fzavipes (Norton), the aphid Macrosiphum euphorbiae (Thomas) and a microlepidopteran species of Monochroa .
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds.     

Long-term recovery of bracken (Pteridium aquilinum (L.) Kuhn) after asulam spraying

This paper investigates the effects of a single asulam application, sprayed from the air, on the rhizome biomass, bud density, fronds and carbohydrate reserves of bracken (Pteridium aquilinum (L.) Kuhn) using a time sequence approach. Regression models were used to investigate how these characteristics varied with time after spraying, and were used, where appropriate, to calculate the time taken for full recovery after treatment. Frond density and biomass recovered in approximately eight years, bud numbers in seven, but rhizome biomass and total carbohydrate reserves required 10 to 12 years to recover. The consequences of these results are compared with predictions from a computer model and discussed in relation to the best timing of re-treatment and the management needed for long term control.     

The Morphology and Growth of Pteridium aquilinum var. esculentum (Forst.) Kuhn

Pteridum aquilinum var. esculentum has three main types of shoot;long, transitional, and short. All bear leaves and the shoottypes are distinguishable from one another only by the lengthof the internodes. The shoot structure is plastic, and eachtype may convert into either of the other types if subjectedto an appropriate environmental stimulus. Long shoots contributeabout 50 per cent. of the shoot length and grow all the yearround with peaks of activity in autumn and spring. Short andtransitional shoots grow only in the autumn and winter period.Frond buds appear macroscopically on the rhizome in spring andsummer but do not elongate rapidly till autumn and winter. Frondsemerge in early spring and continue to emerge till autumn. Somesurvive for two summers, but the majority survive only one summerand are killed by the autumn and winter frosts.     

Bracken fern (Pteridium aquilinum L. kuhn) promotes an open nitrogen cycle in heathland soils

Background and Aims

In spite of the broad array of studies conducted on the ecology of bracken fern (Pteridium aquilinum (L.) kuhn), there is currently only a limited understanding of how P. aquilinum alters the soil environment in which it succeeds. P. aquilinum is one of the world’s most aggressive invasive species and is known to effectively invade conservation priority habitats such as Calluna vulgaris (L.) heathland. The aim of this study was to evaluate differences in soil properties between intact stands of C. vulgaris and neighboring P. aquilinum to assess how P. aquilinum alters soil N transformations in a manner that might promote its success.

Methods

Replicate plots in five independently paired stands of P. aquilinum and C. vulgaris were established on land in which P. aquilinum is actively invading. Soils under the two plant types were evaluated for total N, mineralisable N, net nitrification, nitrifier activity, denitrification enzyme activity, polyphenol N complexing capacity, and resin sorption of inorganic N.

Results

Soils under P. aquilinum were consistently higher in NO₃ ^- and NH₄ ⁺ concentrations compared to C. vulgaris. Extractable organic and inorganic N concentrations for soil under P. aquilinum were respectively 65 %, 77 % and 358 % greater in amino N NH₄ ⁺-N and NO₃ ^--N compared to that under C. vulgaris. In-situ net nitrification (NO₃ ^- sorption to ionic resins) was found to be nearly 300 times greater under P. aquilinum than under C. vulgaris.

Conclusions

P. aquilinum alters the soil environment as to create an inorganic N-rich environment that is favorable to its growth and development.     

Observations on the Microanatomy of the Spermatozoid of the Bracken Fern (Pteridium aquilinum)

Salient features of structure of the spermatozoid of a fern (Pteridium aquilinum) have been determined by a combination of visual and ultraviolet microscopy, with electron microscopy of shadow-cast whole mounts and thin sections, using magnifications up to but not exceeding 50,000 diameters. Attention has been concentrated on the arrangement rather than on the internal details of the various parts. The most important component, apart from the spirally wound nucleus, numerous (about 40) cilia, and mitochondria, is a sheet of parallel fibres spirally wound near the surface of a cone of cytoplasm to which all the other major components are in various ways attached. The diameter of the individual fibres is of the order of 200 A. A few details are given of other minor cell constituents including additional mechanical materials, starch-containing leucoplasts, and the smaller cytoplasmic inclusions.     

蕨菜黄酮分离鉴定

采用75%的乙醇提取经乙醚脱脂的蕨菜粉末,提取液回收乙醇后以石油醚、氯仿、乙酸乙酯、正丁醇依次萃取粗分段,硅胶柱层析、乙酸乙酯-甲醇系统对乙酸乙酯部位梯度洗脱,对其乙酸乙酯洗脱部分反复凝胶柱层析获得2个黄酮单体,分别鉴定为紫云英苷(1)、芦丁(2),其中化合物1为首次从蕨菜中分离得到。     

蕨菜乙醇提取物的Ames试验研究

目的：研究蕨菜乙醇提取物的致突变作用,为蕨菜的开发利用提供一定依据;方法：制备蕨菜乙醇提取物,采用Ames试验方法,以50μg/皿敌克松作为诱变剂,分别添加提取物50、100、200、400、800μg/皿,统计回变菌落数;结果：受试物各剂量组回变菌落数均未超过自发回变菌落数的2倍,且无剂量-反应关系;结论：在本实验条件下,蕨菜乙醇提取物无致突变作用.     

Estimates of gene flow, genetic substructure and population heterogeneity in bracken (Pteridium aquilinum)

Bracken [ Pteridium aquilinum (L.) Kuhn] is a cosmopolitan species and is a noxious weed in many areas. Because of its abundance, particularly in Britain, bracken affords an ideal system for investigating various aspects of population genetics and evolution. High mobility of dispersal units (spores) suggests that rates of gene flow among distant populations should be high. Gene flow is a major evolutionary force that influences the genetic structure of populations. To examine the effects of gene flow on population heterogeneity and population substructuring in bracken, starch gel electrophoresis of enzymes was used to provide the necessary genetic database. Allele frequency data at 21 loci were obtained for seven British populations, one Majorcan and one from the eastern United States. A model was employed to estimate the amount of gene flow ( Nm ) at several levels. Gene flow among British populations was extremely high ( Nm = 36.51), one of the highest estimates reported for plants. Among eight European populations gene flow was lower (but still considered high) at Nm = 2.47. Trans-Atlantic gene flow was low ( Nm = 0.0926).
F -statistics were used to assess population heterogeneity and substructuring. The data indicate that, compared with other species, there is very little genetic differentiation among British populations of bracken. Indeed, it appears that the whole island is behaving as a single randommating population. This result is consistent with high levels of gene flow. Only one population (on the Isle of Arran) showed statistically significant genetic substructuring. Habitat heterogeneity on the island and age structure are hypothesized as possible causes of this result.
The data reported here support previous studies demonstrating that bracken is genetically polymorphic and is an outcrossing species.     

Herbivorous arthropods on bracken (Pteridium aquilinum (L.) Khun) in Australia compared with elsewhere

Abstract The herbivorous arthropod fauna of bracken fern (Pteridium aquilinum (L.) Khun), at a site near Sydney, Australia, is described and compared with previously reported bracken faunas in other geographic regions. Monthly sampling over 18 months found 17 species of herbivorous arthropods (15 insect and two mite species) from five orders. At the ordinal level, the mixture differed substantially from the bracken faunas of sites in Britain and Papua New Guinea. Notable was the presence of Thysanoptera and Acari, and the absence of Coleoptera and Hymenoptera. The mixtures of orders/families represented in the site bracken faunas in Britain, and less so in Australia, resembled those in the pool of herbivorous arthropods in those regions. Further, the mixture of orders on bracken was more similar to the mixture of orders on other ferns than to the mixture of orders among herbivorous insects on all plants; such similarity was not evident at family level. Compared with sites in other regions, the Sydney site had an abundance of pinna-sucking species and a dearth of mining species. Differences between regions in feeding niches most occupied tended to correspond with the differences in orders represented. Not all features of the fauna of bracken near Sydney reflected differences in the general herbivorous arthropod fauna of Australia compared with other regions, or differences between the herbivore faunas of ferns and seed plants. Its composition must be attributed in part to stochastic aspects of the speciation of herbivorous arthropods onto host plants.     

The effects of cutting pre-treatments on the performance of asulam on bracken (Pteridium aquilinum)

The performance of asulam was assessed from a field experiment in which bracken (Pteridium aquilinum) was subjected to a variety of cutting pre-treatments prior to spraying with the herbicide. Both cutting bracken twice in the year prior to asulam application, and spraying frond regrowth 10 wk after a single mid-June cut, improved the performance of asulam. Summer cutting removes nutrients and dry matter from the system and reduces frond height, but increases frond density and the number of active buds on the rhizome system. The enhanced efficiency of asulam on pre-cut plots may be due to any one of these factors, or a complex interaction between some (or all) of them. In areas of tall bracken a cutting pre-treatment has the important practical advantage of reducing the height of the canopy, making the subsequent use of ground spraying equipment easier.     

Spatial Distribution and Reproductive Behaviour of a Triploid Braken (Pteridium aquilinum) Clone in Britain

Chromosome counts of 156 in root tip cells of a bracken plantgrowing in a natural British population confirm the first recordof a triploid in this species. Spore and stomatal measurementssupport the contention of earlier work that cell size in correlatedwith ploidy level in ferns, but the plant is unusual in comparisonwith other odd-numbered polyploids in its degree in its of fertility('good' spore and functional gametophyte production). Two-dimensionalmapping based on isozyme electrophoresis reveal substantialspatial dimensions for the triploid, indicating a plant of considerableantiquity.Copyright 1993, 1999 Academic Press Pteridium aquilinum, bracken, triploid, clone, reproduction, spatial distribution, genetics     

Saudi gazelle (Gazella saudiya) is not a subspecies of Dorcas gazelle

Karyotypes of Saudi gazelle (2n = 47 female, 2n = 50/51 male) are presented for the first time. The three karyotypes shown here vary in the numbers of metacentric chromosomes, but the cause of this variation is not yet known. Although Saudi gazelle are often regarded as a subspecies of Dorcas gazelle, the chromosome numbers and karyotypes of Saudi gazelle are too different from Dorcas gazelle (2n = 30 female, 2n = 31 male) for them to be considered a subspecies. It is also unlikely that these species would interbreed. In view of the present findings, the taxonomic status of this highly endangered gazelle needs to be resolved as soon as possible.     

Resistance of Pteridium aquilinum to attack by non-adapted phytophagous insects

Fresh bracken Pteridium aquilinum L. Kühn or crude bracken extracts deterred 9 non-adapted phytophagous insect species from feeding or settling. Feeding deterrent activity to 5 out of 7 insect species was present in crude bracken extracts at all times over the growing season and was significantly highest in May. Sequential isolation and purification of deterrents indicated that the sesquiterpene pterosin F (6-chlorethyl-2,5,7-trimethyl-indan-1-one) occurred in sufficiently high concentrations in late May/early June bracken frond (24–28 mg/kg fresh wt) to be partially responsible for the deterrent effects of crude bracken extracts to two insect species. A number of other fractions had feeding deterrent activity, but these were not characterized or quantified.