蜡样芽胞杆菌对两种病原菌的抑制研究

指出了蜡样芽胞杆菌作为一种有益菌,对多种病原菌有抑制作用。实验研究了蜡样芽胞杆菌的发酵液和提取液对金黄色葡萄球菌及大肠杆菌的体外抑制作用,结果表明:蜡样芽胞杆菌的发酵液对此二种致病菌有明显抑制作用,而上清液基本没有抑制作用。24h后,蜡样芽胞杆菌发酵液对大肠杆菌的抑制作用减弱,而对金黄色葡萄球菌的抑制作用增强。此时,上清液依然没有抑制作用。     

喜树叶提取物的抗菌活性研究

采用滤纸片法研究喜树叶乙醇提取物和水提物对金黄色葡萄球茼（Staphylococcus aureus）、大肠杆菌（Escherichia coli）、枯草杆茼（Bacillus subtilis）、八叠球菌（Sarcina ventriculi）、黑曲霉（aspergillus niger）、木霉（Trichoderma virid）和青霉（Penicillium chrysogenum）的抗菌活性。结果表明,喜树叶乙醇提取物和水提物对细菌有明显的抑制作用,浓度越大抑制效果越好;喜树叶乙醇提取物对3种霉菌都有抑茼效果,水提物对霉菌没有抑制作用。     

5种药用植物提取液对杨树灰斑病抑菌活性研究

为筛选出对杨树灰斑病菌具有抑制作用的中草药抑菌活性物质,采用3次浸渍提取法对丁香、肉桂、厚朴、毛茛、兴安白芷5种中草药进行提取,采用生长速率法和孢子萌发法,测定了提取液对菌丝生长和孢子萌发的影响。结果表明,5种药用植物提取液对杨树灰斑病原菌均有不同程度的抑制作用,其中丁香、肉桂、兴安白芷提取物对病原菌的菌丝生长抑制效果较好,丁香提取液浓度在16 mg/mL时,对病菌菌丝生长抑制率可达到98.02%,同样浓度的肉桂、兴安白芷提取液抑制率也可达到91%以上;5种药用植物提取液对孢子萌发抑制作用强于对菌丝生长的抑制作用,其中丁香、毛茛对病原菌的孢子萌发抑制效果最好。说明5种药用植物75%乙醇提取液中含有抗菌成分,为生物防治杨树灰斑病提供参考。     

2种桉树插穗内酚酸类物及相关酶活性比较

以扦插生根困难的邓恩桉和易生根的尾巨桉无性系U9为研究对象,分别从受试材料中酚酸类物质及相关酶活性进行了研究。结果表明：邓恩桉和U9插条提取液酸度及主要酸类物质的种类相近,而邓恩桉插条提取液中酚类物质含量及过氧化物酶（POD）活性明显偏高,吲哚乙酸氧化酶（IAAO）和多酚氧化酶（PPO）活性偏低。通过GC-MS分析,U9提取液中同时存在具有抑制和促进作用的酚类物质,而邓恩桉提取液中仅存在具有抑制作用的一元酚。初步认为,酸类物质对邓恩桉插条生根的抑制作用不明显,而酚类物质中的一元酚对邓恩桉插条生根可能具有一定的抑制作用,且IAAO、POD及PPO活性对邓恩桉插穗生根影响较大。     

鱼腥草不同部位抑菌作用的研究

以鱼腥草为材料,石油醚为溶剂,设计L9(34)正交实验提取方法,以金黄色葡萄球菌、痢疾杆菌、大肠杆菌、酵母菌、青霉菌为供试菌种,进行抑菌实验,研究鱼腥草抑菌活性成分的最佳提取方法及其不同部位的抑菌作用和最小抑菌浓度。结果表明:最佳提取方法为1∶25的料液比,50℃的提取温度,4 h的提取时间;鱼腥草全株均具有抑菌活性,其中地下茎提取液对金黄色葡萄球菌、大肠杆菌、酵母菌的抑制作用最强,最小抑制浓度分别为0.04 g/mL、0.06 g/mL、0.06 g/mL,叶的提取液对痢疾杆菌的抑制作用最强,最小抑制浓度为0.08 g/mL,各提取液对青霉菌的抑制作用均不明显。     

“青引”燕麦中皂甙提取工艺研究

研究利用索氏浸提法提取燕麦中皂甙工艺条件。以乙醇-正丁醇为溶剂,以皂甙RC为标准品,采用分光光度法定量分析燕麦提取液中总皂甙含量,采用正交试验对料液比、乙醇浓度、浸提温度对提取率的影响。结果表明,正交试验最佳提取条件为料液比：1∶7;乙醇浓度：70%;浸提温度：70℃,提取率为1.716%;主次顺序依次为：料液比〉浸提温度〉乙醇浓度。该方法操作方便,简单易行,具有推广应用价值。     

火炬树叶提取物对5种微生物抑菌活性的研究

运用滤纸片法、二倍稀释法和平板涂布法,研究了火炬树叶的鲜汁液、水提液、畔提液对常见致病菌大肠杆菌、金黄色葡萄球菌、绿脓杆菌、木霉、黑曲霉的体外抑菌活性.结果显示:提取物对供试微生物均有抑制作用,水提液的抑菌效果最好,且对金黄色萄萄球菌的抑菌作用优于其他4种供试微生物.此外,火炬树叶提取液热稳定性较好,经121℃灭菌15min后仍具有较强杀菌作用.     

野生蒲公英抑菌活性研究及其袋泡茶的研制

采用回流提取法制备蒲公英提取液,并对其抑菌力、热稳定性及最低抑菌浓度进行测定的结果表明:蒲公英提取液对常见污染菌,即金黄色葡萄球菌、变形杆菌有较强的抑制作用;对汉逊氏酵母菌、毕赤氏酵母有一定的抑制作用;但对黑曲霉和青霉抑制作用较弱,最后研制了蒲公英袋泡茶的制作工艺。     

樟油的提取及其抑菌性研究

通过蒸馏法从樟树的树根、树枝、鲜叶及落叶中提取樟油,然后将用蒸馏法从落叶中获得的樟油和用丙酮浸提法从落叶中获得的提取物分别配制成不同浓度的水溶液,采用抑菌圈法分别对常见的几种细菌进行抑菌研究,结果表明落叶中的得油率最高,用蒸馏法获得的樟油对大肠杆菌(Escherichia coli)、普通变形杆菌(Proteus vulgaris)、金黄葡萄球菌(Staphylococcus aureus)有一定的抑菌作用,其最低抑菌浓度(MIC)在0.125~0.25 g.mL-1之间,而丙酮浸提液对上述细菌的生长几乎没有抑制作用。     

木麻黄乙醚浸提液的分离及鉴定

采用GC—MS技术,比较木麻黄凋落物、根和根际土壤3种浸提液的成分差异和含量差异的结果表明：3种浸提液（凋落物、根系和根际土壤乙醚浸提液）中的有机化舍物化学成分有明显差别,凋落物和根际土壤的乙醚浸提液中特有成分分别为维生素E和苯酚;3种浸提液中都含有的成分是羽扇烯酮和羽扇豆醇;羽扇烯酮在浸提液中含量由高到低依次为：凋落物（7．39％）,根际土壤（2．65％）,根（2．28％）;羽扇豆醇在浸提液中含量由高到低依次为：凋落物（3．22％）,根际土壤（2．65％）,根（2．0％）。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。