Effects of the subterranean herbivorous rodent Spalacopus cyanus on herbaceous vegetation in arid coastal Chile

Summary The impact of the subterranean herbivorous rodent Spalacopus cyanus Molina on the herbaceous vegetation was studied by comparing biomass, species richness and species diversity at the end of the growing season in areas with and without burrows in coastal arid Chile. Total biomass was 60% higher in areas with burrows. This difference was mainly due to the large increase of Mesembryanthemum cristallinum L., a succulent prostrate annual herb. Unexpectedly, bulb biomass of geophytes, eaten by Spalacopus, did not differ between areas. However, in areas with burrows bulbs of geophytes were more numerous and smaller. It is possible that burrowing activities facilitate the occurrence of new small bulbs through seed germination. Species composition and diversity did not differ greatly between areas. Burrowing activities by Spalacopus, the life cycle of Mesembryanthemum, and climate seem to be the most important factors determining species abundance and diversity of herbs in this system.This is a contribution of the Program of Arid Zone Studies of Universidad de La Serena     

Flora, vegetation, and soil in broadleaved ancient and planted woodland, and scrub on RøsnÆs, Denmark

9 small ancient woodlands (>200 years), 9 planted woodland sites (25 — ca. 100 years), and 6 sites in grazed scrub (ca. 100 years) on the RøsnÆs peninsula, Denmark, showed characteristic differences: in ancient woodland, the tree and shrub layer was fairly rich, the field layer rather poor in species. The dominance of spring flowering geophytes, the abundance of Anemone nemorosa , and the occurrence of Corylus avellana and Polygonatum multiflorum were characteristic. pH of the soil was relatively low, organic matter content high, and light intensity at the forest floor in summer low. In planted woodland there was more light, and the field layer was rich in short-lived species, but poor in spring flowering geophytes. Many woodland species were rare in planted woodland, some did not at all occur there, and none were specific for this type of woodland. The scrub was marked by grazing and a strong relief, hence pH was high and organic matter content low. The field layer was rich both in shortlived species and in spring flowering geophytes. — It is suggested that ancient woodland species (i.e. species restricted to or preferably occurring in woodlands existing prior to the enclosure ca. 200 years ago) is a heterogenous group, consisting of a) species favoured by traditional woodland management; b) species restricted to woodlands where specific environmental (e.g. soil) conditions have had sufficient time to develop; c) species with limited ability to spread or establish; or d) species which in ancient woodland are represented by small and scattered populations.     

Nitrogen cycling and storage in <Emphasis Type="Italic">Gagea spathacea</Emphasis> (Liliaceae): ecological insights for protecting a rare woodland species

Strategies to globally protect biological diversity are often hampered by an insufficient ecological knowledge about target species. This also applies to Gagea spathacea (Liliaceae), a ‘vulnerable’ woodland spring geophyte with a distribution largely restricted to the lowlands of Central Europe. We studied whether the species’ linkage to highly fertile forest soils is related to its high nitrogen (N) demands during its short developmental cycle. We hypothesized that the species exhibits a highly efficient N (re)cycling strategy, characterized by efficient resorption of N from the leaves and reallocation to bulbs at the end of the growing season. To test this assumption, we conducted a ¹⁵N tracer experiment and quantified ¹⁵N flows between soil, leaves, bulbs, and roots. Our findings support our hypothesis that G. spathacea is exceptionally efficient in recycling N, shown by the resorption of 68% of leaf N and its reallocation to bulbs at the end of the growing season. After 6 weeks of growth the plant showed a distinct shift in its N metabolism: The C:N ratio of leaves strongly increased and those of bulbs decreased, leaf ¹⁵N enrichment and recovery started to decrease, while total plant ¹⁵N recovery remained constant, indicating no further N uptake from the soil. Leaf N reallocation to bulbs was accompanied by a twofold increase of the bulbs’ biomass. Because of the stenoecious behaviour of G. spathacea, a careful protection and sustainable management of G. spathacea forest habitats is necessary, particularly in its Central European core area.     

Neoseiulus paspalivorus,a predator from coconut,as a candidate for controlling dry bulb mites infesting stored tulip bulbs

The dry bulb mite, Aceria tulipae, is the most important pest of stored tulip bulbs in The Netherlands. This tiny, eriophyoid mite hides in the narrow space between scales in the interior of the bulb. To achieve biological control of this hidden pest, candidate predators small enough to move in between the bulb scales are required. Earlier experiments have shown this potential for the phytoseiid mite, Neoseiulus cucumeris, but only after the bulbs were exposed to ethylene, a plant hormone that causes a slight increase in the distance between tulip bulb scales, just sufficient to allow this predator to reach the interior part of the bulb. Applying ethylene, however, is not an option in practice because it causes malformation of tulip flowers. In fact, to prevent this cosmetic damage, bulb growers ventilate rooms where tulip bulbs are stored, thereby removing ethylene produced by the bulbs (e.g. in response to mite or fungus infestation). Recently, studies on the role of predatory mites in controlling another eriophyoid mite on coconuts led to the discovery of an exceptionally small phytoseiid mite, Neoseiulus paspalivorus. This predator is able to move under the perianth of coconuts where coconut mites feed on meristematic tissue of the fruit. This discovery prompted us to test N. paspalivorus for its ability to control A. tulipae on tulip bulbs under storage conditions (ventilated rooms with bulbs in open boxes; 23 °C; storage period June–October). Using destructive sampling we monitored predator and prey populations in two series of replicated experiments, one at a high initial level of dry bulb mite infestation, late in the storage period, and another at a low initial dry bulb mite infestation, halfway the storage period. The first and the second series involved treatment with N. paspalivorus and a control experiment, but the second series had an additional treatment in which the predator N. cucumeris was released. Taking the two series of experiments together we found that N. paspalivorus controlled the populations of dry bulb mites both on the outer scale of the bulbs as well as in the interior part of the bulbs, whereas N. cucumeris significantly reduced the population of dry bulb mites on the outer scale, but not in the interior part of the bulb. Moreover, N. paspalivorus was found predominantly inside the bulb, whereas N. cucumeris was only found on the outer scale, thereby confirming our hypothesis that the small size of N. paspalivorus facilitates access to the interior of the bulbs. We argue that N. paspalivorus is a promising candidate for the biological control of dry bulb mites on tulip bulbs under storage conditions in the Netherlands.     

细叶百合的生物量和营养分配

 以栽培的2年生细叶百合（Lilium pumilum）为材料,于2000年的生长季从蕾期至种子成熟期进行6次取样,对其各器官生物量和氮、磷元素的配置进行了动态研究。结果表明,细叶百合虽然以种子繁殖为主,但在整个生长季用于生殖器官的生物量投资的比例并不很大,大量干物质分配到地下器官鳞茎中（平均为60.17%）;茎、叶的生物量分配比例仅次于鳞茎;雄蕊生物量分配比例明显高于雌蕊。在叶萌动及展叶初期植株全氮百分含量最高;从春季萌动至秋季果实成熟,叶中的氮呈逐渐递减的趋势;茎和生殖器官的全氮含量在蕾期最大;生殖器官与叶、鳞茎的全氮含量相关显著。磷在生殖器官的含量较高,这与磷在植物有性生殖过程中的重要作用相一致;生殖器官与茎的全磷含量相关显著。地下器官全氮、全磷随季节变化有增多的趋势;地上各器官全氮、全磷相关显著,随季节变化有明显减少的趋势。     

Desert geophytes under dew and fog: The “curly-whirlies” of Namaqualand (South Africa)

In the semidesert of Namaqualand and adjacent regions of the former Cape Province, South Africa, there occurs an assemblage of geophytes belonging to eight monocot families and some Oxalis species that exhibit special morphological adaptations of their aerial parts to harvest and absorb water from dew and fog, the main source of moisture in this region. Most of them pass their vegetative phase in winter. Leaves and in some cases axes, display a circinate, helical, tortuose, or serpentine shape and/or their margins are undulate or crispate, or (and) are provided with a ciliate or fimbriate pilosity of uncommon appearance. These morphomes, rare elsewhere among monocotyledons, promote an increased deposit of dew and fog by enlargement of surfaces and edges, keeping at the same time the overall size of the leaves restricted. They improve the water budget of these plants in three ways: (1) remnant water on the aerial parts retards the transpiration stress at day-time; (2) although special organs for direct absorption seem to be absent, field and laboratory tests show, that considerable uptake of water occurs but in quantities not exceeding that capacity found in many non-desert plants; (3) the water harvest of the leaves dripping to the soil and reaching the root zone, where it is stored in tubers, bulbs, corms and rhizomes, appears to be the main contribution. Experiments using artificial, directional fog and metal models imitating the natural profiles demonstrate that a surplus of water in efficiency rates of 0.1-66% is collected by the various surface types compared to a standard model with a non-sculptured (plain) frontal surface of the same size. The higher rates are sufficient to moisten the underlying soil down to the rhizosphere. The circumference of roots and storage organs probably does not exceed the area shadowed by the foliage. Namaqualand geophytes with such morphologies apparently form a novel desert biotype: as mesophytes they represent a distinguished strategy besides that of succulents and other xerophytes.     

Biological Control of the Bulb Mite, Rhizoglyphus robini , by the Predatory Mite, Hypoaspis aculeifer , on Lilies: Predator-Prey Dynamics in the Soil, under Greenhouse and Field Conditions

We tested the capacity of the soil-dwelling predatory mite, Hypoapsis aculeifer , to control mites attacking lily bulbs. Experiments in the greenhouse and in the field showed that in the absence of predatory mites populations of the bulb mite, Rhizoglyphus robini , on lily bulbs increased, whereas the release of predatory mites either slowed down the increase - as observed in the field - or caused the bulb mites populations to decrease - as observed in the greenhouse. In all cases the population of predatory mites increased as long as bulb mite densities were not too low. However, within the first week after predator release there was usually a sharp decline to 10-40% of the original number released. Greenhouse experiments on intact lily bulbs in pots, boxes and 1 m 2 plots with peat soil showed that when released in a ratio of 1 predator to 2 or 5 prey, the predatory mite, Hypoaspis aculeifer , suppressed populations of bulb mites to less than 10 individual per bulb within 6 weeks. Elimination of bulb mites was observed only when the predator-to-prey ratio at release was equal to 3:1. Field experiments in 2 m 2 plots with intact bulbs in rather compact sandy soil showed that when released in ratio of 1 predator to 1 or 2 prey, the predatory mite, H. aculeifer , did not cause the population of bulb mites to decrease, but it did reduce their population growth. The initial predator-to-prey ratios required to achieve suppression (ca 1:2) or elimination (3:1) in the soil environment are much higher than those required for bulb mite elimination when lily bulb scales were embedded in a medium of vermiculite (ca 1:20). Among the possible causes are: (1) the initial losses of predators in the greenhouse and even more so in the field due to mortality and/or emigration from the experimental plots; (2) the lower temperatures in the greenhouse and especially in the field, which slow down the growth and predation processes and thereby delay prey extinction; and (3) the spatial complexity of the soil environment which creates refuges for the bulb mites.     

Evidence of a novel allergenic protein Narcin in the bulbs of Narcissus tazetta

Several plant-derived allergens have been identified which result in the formation of immunoglobulin E antibodies. Primarily, these allergens belong to the protein families including seed storage proteins, structural proteins and pathogenesis-related proteins. Several allergens are also reported from flower bulbs which cause contact dermatitis. Such symptoms are highly common with the bulb growers handling different species of Narcissus. Narcissus toxicity is also reported if the bulbs are consumed accidentally. The present study aimed to characterize the protein from the bulbs of Narcissus tazetta responsible for its allergenic response. A 13 kDa novel allergenic protein, Narcin was isolated from the bulbs of Narcissus tazetta. The protein was extracted using ammonium sulfate fractionation. The protein was further purified by anion exchange chromatography followed by gel filtration chromatography. The N-terminal sequence of the first 15 amino-acid residues was determined using Edman degradation. The allergenicity of the protein was measured by cytokine production using flow cytometry in peripheral blood mononuclear cells. Further estimation of total IgE was performed by ELISA method. This novel protein was found to induce pro-inflammatory cytokines and thus induce allergy by elevating total IgE level. The novel protein, Narcin isolated from Narcissus tazetta was found to exhibit allergenic properties.     

Interactive effects of soil nutrient heterogeneity and belowground herbivory on the growth of plants with different root foraging traits

Aims

Plants with precise root foraging patterns can proliferate roots preferentially in nutrient-rich soil patches. When nutrients are distributed heterogeneously, this trait is often competitively advantageous in pot experiments but not field experiments. We hypothesized that this difference is due to belowground herbivory under field conditions.

Methods

We performed pot experiments using seedlings of Lolium perenne (a more precise root foraging species) and Plantago lanceolata (a less precise root foraging species). The experiment had a two-way factorial randomized block design, with nutrient distribution pattern (homogeneous or heterogeneous) and belowground herbivore (present or absent) as the two factors. Each pot contained one seedling of each species.

Results

With no herbivore present, plant biomass was smaller in the heterogeneous nutrient treatment than in the homogeneous treatment in P. lanceolata, but not in L. perenne. Under homogeneous nutrient distribution, plant biomass was lower in both species with a herbivore present than with no herbivore. Under heterogeneous nutrient distribution, biomass reduction due to herbivory occurred only in L. perenne.

Conclusions

Roots of the precise root foraging species were grazed more under the heterogeneous nutrient distribution, suggesting that the herbivore more efficiently foraged for roots in nutrient-rich soil patches.     

皇甫川流域大型土壤动物对不同水土治理措施的响应

为了解大型土壤动物对不同水土治理措施的响应,于2008年5～9月,采用手拣法采集大型土壤动物,以内蒙古皇甫川流域人工工松树林、人工杨树林、人工锦鸡儿灌木林、人工沙打旺草地、撂荒地和农田6种不同土地利用方式为采样地,分析了大型土壤动物群落的组成、多样性和季节动态特征.共捕获大型土壤动物1 653只,隶属于1门3纲8目34...     

Efficacy of Selected Nonvolatile Nematicides on Control of Ditylenchus destructor in Iris

Greenhouse and field tests established that fenamiphos at 6.7 and 13.4 kg ai/ha applied in a 30-cm band directly on iris bulbs at planting effectively controlled Ditylenchus destructor. Aldicarb at rates of 5.6 to 11.2 kg ai/ha was less effective. Carbofuran, fensulfothion, and oxamyl at 6.7 to 13.4 kg ai/ha were ineffective. When applied on the bulbs, fenamiphos (granular or liquid) reduced nematode infection from 31 to 0.6% as determined by visual inspection of bulbs at harvest. Populations of D. destructor were reduced from 5.7 nematodes/g of fresh weight of bulb tissue to 0.04, 0.05, and 0.14 with applications of 13.4, 6.7, and 3.3 kg ai/ha fenamiphos, respectively. The most effective treatment was fenamiphos (granular or liquid) applied in a 30-cm band directly on the bulbs at time of planting.     

Biomass Allocation of Erythronium americanum Populations in Different Irradiance Levels

The forest herb Erythronium americanum was collected from threeNew Jersey habitats and grown in 100%, 43%, or 23% glasshouselight to determine if biomass allocation responses to irradiancediffered between populations. Shaded plants had longer petioles,produced fewer runners, and had greater specific leaf areasthan unshaded plants; these responses did not differ significantlyamong populations. All populations produced smaller bulbs whengrown in shade. Over all light treatments, mean leaf area ofplants from a stable, established site was greater than thatof plants from others. In 100 % light, these plants had thegreater bulb growth. The simple architecture of Erythroniummay constrain morphological responses to the light environment. Erythronium americanum(Ker.), forest herb, biomass allocation, light intensity     

Evaluation of Hot Water Treatments for Management of Ditylenchus dipsaci and Fungi in Daffodil Bulbs

Treatment of daffodil (Narcissus pseudonarcissus) bulbs in a 0.37% formaldehyde water solution at 44 C for 240 minutes is a standard practice in California for management of the stem and bulb nematode, Ditylenchus dipsaci. Recent concern over the safety of formaldehyde and growers'' requests for a shorter treatment time prompted a reevaluation of the procedure. The time (Y, in minutes) required to raise the temperature at the bulb center from 25 to 44 C was related to bulb circumference (X, in cm) and is described by the linear regression Y = -15 + 3.4X. The time required for 100% mortality of D. dipsaci in vitro without formaldehyde was 150, 60, and 15 minutes at 44, 46, and 48 C, respectively. Hot water treatment (HWT) with 0.37% formaldehyde at 44 C for 150 minutes controlled D. dipsaci and did not have a detrimental effect on plant growth and flower production. Shorter formaldehyde-HWT of 90, 45, and 30 minutes at 46, 48, and 50 C, respectively, controlled D. dipsaci but suppressed plant growth and flower production. Fungal genera commonly isolated from the bulbs in association with D. dipsaci were Penicillium sp., Fusarium oxysporum f. sp. narcissi, and Mucor plumbeus, representing 60, 25, and 5%, respectively, of the total fungi isolated. These fungi caused severe necrosis in daffodil bulbs. HWT at 44 C for 240 minutes reduced the number of colonies recovered from bulbs. The effects of formaldehyde, glutaraldehyde, and sodium hypochlorite in reducing the population of fungi within bulbs were variable. Satisfactory control of D. dipsaci within bulbs can be achieved with HWT of bulbs at 44 C for 150 minutes with 0.37% formaldehyde or at 44 C for 240 minutes without chemicals.     

喀斯特地区不同土地利用方式对土壤有机碳、全氮以及微生物生物量碳和氮的影响

以广西环江大才为代表,选择亚热带典型喀斯特峰林谷地样区,通过对样区土壤进行密集采样和测定分析,研究了土地利用方式对土壤有机碳（O_C）和全氮（TN）含量及土壤微生物生物量碳（B_C）和氮（B_N）含量的影响.结果表明,3种土地利用方式下,土壤有机碳含量在稻田和林地中基本相同,而旱地显著低于稻田和林地.土壤全氮含量为稻田显著高于林地,而林地显著高于旱地.土壤微生物生物量碳含量为稻田显著高于林地,林地显著高于旱地.土壤微生物生物量氮含量在稻田和林地中基本相同,而旱地显著低于稻田和林地.旱地土壤pH值显著低于稻田和林地土壤.3种土地利用方式下,土壤微生物生物量碳与土壤有机碳、土壤微生物生物量氮与全氮含量之间均呈显著的正相关关系.土壤微生物生物量碳和氮含量可以作为评价喀斯特地区土壤质量和肥力的指标之一,对土地利用方式响应较为敏感.     

Food availability and foraging by wild colonies of Damaraland mole-rats (Cryptomys damarensis): implications for sociality

We investigated some of the ecological determinants of sociality in the Damaraland mole-rat, including the spatial distribution and biomass of resources (geophytes) available to foraging Damaraland mole-rats in partly vegetated sand dunes in the Kalahari and in grasslands near Dordabis, Namibia, and the foraging behaviour and residency characteristics of colonies at Dordabis. In both study areas, the geophytes had a clumped distribution, but the highest coefficients of dispersion and mean biomass occurred in the Kalahari where the principal food was the gemsbok cucumber. However, because the coefficient of digestibility was lower in geophytes from the Kalahari than from Dordabis, and the mole-rats only ate about half of a gemsbok cucumber, there was less energy available to mole-rats in the Kalahari. At Dordabis, large established colonies occur in the areas with the richest resources and remain resident in the same area for many years; within this area they search (blindly) for food during brief periods when the soil, at burrow depth, is moist and easily worked. Initially, long straight burrows are dug and few bulbs are taken; once the soil dries, minor changes are made to the burrow system as the mole-rats exploit the food patches they located immediately after the rain. Our results show that the characteristics of the resources, and the short time interval during which location of new resources is possible, favour group living; however, the constraints imposed by these features affect large and small colonies in different ways. Small colonies are more likely to fail than large ones and some crucial factors in the survival of these newly formed colonies are the richness of the area in which their burrows are located, and the size of the colony work force available to locate the food. Received: 6 May 1997 / Accepted: 21 August 1997     

Nitrogen uptake and utilisation as a competition factor between invasive Duchesnea indica and native Fragaria vesca

The Indian mock strawberry [Duchesnea indica (Andrews) Focke] is an invasive plant in several regions of central Europe and Germany. In order to explore its competitive ability, we compared it with the native woodland strawberry (Fragaria vesca L.) by growing it alone as well as in intra- or inter-specific competition in a pot experiment under greenhouse conditions. Nutrient solution was added several times at two nitrogen (N) levels. One addition involved ¹⁵N labelling to determine whether the competition of both plant species depends on their ability to acquire N from soil. Duchesnea had a higher biomass production than Fragaria when grown in nutrient-rich soil, both in competition and as a solitary plant. Under N-poor conditions, root interference could change this superiority due to limited soil space. After 65 days of growth, total plant dry weight, total N content and ¹⁵N content in the plant tissues were determined. The results show that the predominance of Duchesnea in biomass production was confirmed at high, but not at low N availability. The assimilate partitioning strategy of Duchesnea differs from that of Fragaria: the former generally had a higher shoot-to-root ratio. The N content in shoots and roots was affected only by N addition but not by competition or species. Duchesnea allocated more N to the leaves, Fragaria to the roots. The amount of ¹⁵N taken up was nearly equal for both species. In relation to root biomass, Duchesnea had a higher specific uptake rate at low N addition because of the higher root biomass in Fragaria. The roots of Fragaria and Duchesnea did not affect each other when grown together. We conclude that the invasive potential of Duchesnea is only poorly related to the N uptake rate or to better root competition for N. In N-rich environments, however, Duchesnea is highly competitive because of the preferred investment in shoot biomass. Therefore, environments with increased N deposition, i.e. from anthropogenic sources, could promote the invasive potential of Duchesnea.     

Performance of Anisantha (Bromus) tectorum and Rumex acetosella in sandy calcareous soil

Many plants are adapted to an eroded landscape with a large proportion of virgin soil. Open and disturbed soils are today almost only restricted to agricultural fields with high loads of fertilizers. We conducted a pot experiment in order to investigate growth and nutritional constraints of one calcicole species, Anisantha (syn. Bromus) tectorum, and one calcifuge species, Rumex acetosella, in decalcified topsoil and recently exposed calcareous subsoil from a field experiment in sandy grassland. In the pot experiment we implemented one treatment where we limed topsoil with CaCO₃ to the same amount as in subsoil.The subsoil had approximately 10% CaCO₃ and both species grew less in this soil compared to the topsoil, which had less than 1% CaCO₃. Germination rate of A. tectorum was higher in subsoil than in topsoil or limed topsoil. P fertilization of the limed topsoil counteracted the negative liming effect for A. tectorum, but only partly so for R. acetosella. P fertilization of subsoil increased the shoot biomass of A. tectorum, but not of R. acetosella. P concentration in plants was not reduced when growing on subsoil or limed topsoil compared to topsoil. The results show that lime addition may reduce the P availability also to calcicole species such as A. tectorum and we found indications for that Ca toxicity may be a causing factor for the calcifuge behavior of R. acetosella. The significance of the results for conservation management practices in sandy grasslands is discussed.     

不同利用方式下潮棕壤交换性钙镁的剖面分布

在水稻田、玉米地、撂荒地和人工林地4种土地利用方式下,对潮棕壤0～150 cm土层中土壤交换性钙(Ca)和交换性镁(Mg)的剖面分布及Ca/Mg的变化进行了比较研究.结果表明：不同利用方式下土壤交换性Ca含量及储量差异不明显;林地各土层的土壤交换性Mg含量均显著高于水稻田（P<0.05）;交换性Mg储量大小依次为林地、玉米地、撂荒地和水稻田（P<0.05）.不同利用方式交换性Ca/Mg随土层深度的增加而降低,40 cm以下土层水稻田Ca/Mg显著高于其他3种利用方式（P<0.05）.土壤生态系统中Mg的优先固持、土壤管理以及植物自身的特性如生物量的循环速率、生物量在地上部分和地下部分的分配、根系的分布等,对土壤剖面中交换性Ca和交换性Mg的构成以及土壤交换性Ca库和Mg库的重建等起到重要作用.     

A comparison of the pharmacological properties of garden cultivated and muthi market-sold Bowiea volubilis

Biological activities of petroleum ether (PE), dichloromethane (DCM), 70% ethanol (EtOH) and water extracts of Botanical Garden-grown (BG) and muthi market-sourced (MM) Bowiea volubilis bulbs were compared. Bulb extracts were subjected to the microdilution technique using five test organisms for antimicrobial activity and cyclooxygenase (COX-1 and -2) inhibition as well as the Ames test for potential mutagenicity. Overall, both the MM and BG bulb extracts demonstrated a comparatively weak antimicrobial potency. The best minimum inhibitory concentration (MIC: 1.56 mg/ml) was detected in the MM bulb water extract against Candida albicans. In both MM and BG bulbs, 63% of the extracts, particularly the non-polar solvent extracts, exhibited a high (> 70% inhibition) COX-1 and -2 inhibitory activity. Both MM and BG bulb extracts were not mutagenic against the Salmonella typhimurium TA98 tester strain. Current findings indicate the potential substitution of cultivated B. volubilis bulbs (BG) for the wild population (MM) which is often utilized and preferred in traditional medicine. Inevitably, this will contribute to the conservation of the species as the strain on the wild population due to overharvesting will be alleviated.     

内生真菌感染对禾草宿主生境土壤特性和微生物群落的影响

以羊草(Leymus chinensis)-内生真菌共生体为研究对象, 分别在野外样地和室内盆栽两种实验条件下研究了内生真菌感染对土壤特性和微生物群落结构的影响。结果显示：在处理时间较长并伴随有枯落物分解的羊草样地中, 内生真菌感染促进了土壤氮(N)的积累, 提高了30天培养时间内土壤初始碳(C)矿化速率和前3天土壤矿化量和土壤矿化总量; 而在处理时间较短且没有地上枯落物分解的盆栽羊草中, 内生真菌感染对土壤的C、N含量及C矿化均无显著影响。无论是野外样地还是室内盆栽实验, 内生真菌感染均未引起土壤微生物磷脂脂肪酸种类的变化, 但内生真菌感染均有提高土壤微生物生物量的趋势, 内生真菌显著增加了盆栽羊草土壤中细菌、革兰氏阴性细菌、真菌磷脂脂肪酸含量和磷脂脂肪酸总量, 增加了羊草样地土壤中革兰氏阳性细菌和放线菌的磷脂脂肪酸含量。总体看来, 内生真菌感染能够改变土壤N积累和C矿化率, 并且改变土壤中微生物群落的结构, 这有助于进一步认识内生真菌与羊草之间的共生关系及其在生态系统C、N循环中所起的作用。