国外松枯梢病病原菌生物学特性的研究

对国外松枯梢病病原茵(Diplodia pinea,又名 Sphaeropsis sapi-nea)从分生孢子萌芽、菌丝体生长及产生子实体所需要的条件三个方面开展了生物学特性的研究。结果表明无论是自然界或人工诱导的分生孢子在清水中均不易萌芽,分生孢子萌芽需要补充一定的营养条件,以10%的松针汁最有利于萌茅,其次为2%的葡萄糖液。菌丝体在10%松针汁+PDA 及 PSA 培养基上生长最快。分批在不同温度组中测定孢子萌芽及菌丝体生长的温度条件,表明从4℃起孢子萌芽及菌丝体生长即可微度进行,孢子萌芽最适温度为27-29℃,菌丝体生长最适温度为26-27℃,38℃高温并不影响孢子萌芽率,35-38℃时芽管及菌丝体生长严重受阻。孢子致死温度达42℃以上,说明该菌对高温的耐受力很强。孢予在 pH4-10时均可萌芽,以6-8最为适宜。分生孢子萌芽需要的最低湿度为80%,高湿度有利于孢子萌芽,但并不一定需要自由水;分生孢子4个月后发芽率仍很高,一年后仍有有一定的萌芽率。黑暗及室内自然光下人工培养不易产生子实体,但在萤光灯下7-15天可以诱导出子实体。以松针段、松梢、PSA 及10%松针汁+DA 培养基最有利于子实体及分生孢子的产生。以上试验结果表明该菌在我省对温度的适应范围较其他报道要广,其他特性也表明该菌适应性、生命力均较强,为该病害在我省普遍严重发生的原因之一,各地与我们在对该菌生物学研究中结果的差异很可能由于病原菌的变异造成。     

油茶饼病病原菌生物学特性的初步研究

从油茶饼病病叶上分离得到一真菌,经鉴定为油茶外担子菌[Exobasidium gracile(shirai)Syd]。并对其进行了生物学特性测定。研究结果表明:该菌菌丝生长及孢子萌发在15~31℃的范围内均能生长,25~28℃为其适宜的生长温度,最适温度是25℃,低于10℃或高于35℃停止生长;在pH 3~7的范围内均能生长,适宜生长的pH范围为5~6,最适的pH为5.5,pH低于2或高于8停止生长,最适的相对湿度是100%。     

松树枯梢病潜伏侵染的研究

研究表明在火炬松、湿地松、短叶松和马尾松健康梢上整年都能分离到松枯梢病菌,其中在火炬松上的得菌率为15％—37．7％,且大多数月份高于20％;湿地松上的得菌率稍低于火炬松,为7．5％～29．1％;短叶松梢上的得菌率是13．8％—57．1％,月份之间的差异较大;马尾松得菌率最低,为9．7％—22．4％,多数分离得菌率低于20％。健康梢的不同部位得菌率有一定差异,枝和新梢较高,芽稍低,叶最低。在1年中,健康梢上得菌率有3个高峰期,即4—5月、7—8月和10—11月,是潜伏侵染的的主要时期。将健康芽和梢进行诱发培养,lOd后组织块上及周围产生松枯梢病菌的分生孢子器,得菌情况与常规分离相似。在当年孢子散发之前,对健康梢套袋隔离试验,发现套袋梢仍会发病,说明在发病的春梢中,有一部分是由于潜伏侵染的松枯梢病菌造成的。从而证明松枯梢病菌在火炬松、湿地松、短叶松和马尾松上普遍存在潜伏侵染。     

樟子松枯梢病病原菌生物学特性的研究

研究表明,樟子松枯梢病病原菌分生孢子的萌发与通气和光照条件关系不大,无需外界供给养料。孢子的萌发主要取决于温度和湿度条件。在水中, 孢子萌发的温度范围为１５ ～３５ ℃,最佳温度为２５ ℃。在２５ ℃条件下,孢子在４ ｈ 以内即可萌发。在相对湿度达９０ ％ 以上时,孢子萌发率随湿度增大而升高。６ ～８ 月是辽宁章古台地区病菌萌发侵染的适宜时期,化学防治应在此期间进行。     

云杉梢斑螟生物学特性的观察

云杉梢斑螟Dioryctirin schutzeella Fuchs在祁连山林区每年发生1代,以幼虫在新梢基部芽鞘内及针叶中越冬,翌年5月上旬开始活动,6月上、中旬为危害盛期,老熟幼虫在被害残梢虫巢内结茧化蛹。在云杉萌芽抽梢期喷洒杀螟松、敌敌畏、辛硫磷、溴氰菊酯等药剂,防治2—4龄幼虫,杀虫率90％以上;喷施苏云金杆菌含孢子3—4亿/毫升,防治效果75％左右。     

雪松针叶枯斑病病原鉴定及其生物学特性研究

按分离→接种→再分离的柯赫原则对昆明市人工栽培雪松上的一种新病害进行研究，根据培养性状和形态特征鉴定为极细枝孢(Cladosporium teruissinum Cooke)。对该菌的生物学特性研究结果为：生长的最佳C源为葡萄糖，对N源和维生素均不能很好地利用，在PDA培养基上生长的适宜温度为15～25℃，最佳温度为25℃，最佳pH值为4，分生孢子在相对湿度为100％才萌发。     

芒果畸形致病菌—亚粘团串珠镰孢的营养学研究

<正> 印度农业研究所真菌与植物病理学研究室的研究人员发现,芒果畸形致病菌—亚粘团串珠镰孢(Fusarium moniliformevar subglutinans)的生长及孢子形成的最适温度为30℃,它在10天之内即达生长极限,生长及孢子形成的最适pH值分别为7和6。 Amitava Mitra等人指出,亚粘团     

杉木枯梢病的发生规律及病原菌生物学特性研究

近年在广东发现的杉木枯梢病是由二极霉引起的为害杉苗的严重病害，病原菌生物学特性测试表明，分子孢子在水滴中萌发最好，２０℃为萌发最适温度，菌线生长的最适温度范围为２０～３０℃，并在ｐＨ３～７的范围内都生长正常，病菌入侵杉梢组织以伤口为主，潜育期２～４天，在合适条件下１０～１５天便可再次侵染，较强光照有助于刺激孢子产生，该病害在每年春季多雨季节开始发生，６～８月流行迅速，１０月以后逐渐减轻，病菌可以菌     

冬枣树皮疱斑病病原菌生物学特性的研究

桃尖炫菌(桃茎点霉菌)Phoma persicae Sacc.单独侵染引起的冬枣树皮疱斑病是冬枣树皮上的一种重要病害。该菌在PDA,OUA,CMA培养基上均生长良好;菌丝生长与孢子萌发的最适温度均为25℃;在pH6时菌落生长最好,孢子萌发最适pH6～7;在光照与黑暗交替(12L∶12D)和24 h黑暗条件下菌丝生长较快,光照对产孢、孢子萌发无影响;不同营养液中,树皮煮汁液中孢子萌发率最高。     

杜松枯梢病的初步研究

根据柯赫氏证病法则和病原菌形态特征证明杜松枯梢病是由桧色二孢Diplodia juniperi Wes-tend.引起的.病原菌的适生温度15～35℃,最适温度30℃,温度低于20℃生长缓慢,低于15℃时完全停止生长.菌丝在pH值5.8～8.2之间均能生长,最适pH为6,偏酸更好.不同的碳源对生长无显著影响,乳糖为最佳碳源.蛋白胨为最佳有机氮源,硝酸钙为最佳无机氮源.     

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.     

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.     

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.     

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。