翅果油树大小孢子发生及雌雄配子体发育

利用常规石蜡切片技术,对濒危植物翅果油树大、小孢子发生及雌、雄配子体发育的过程进行研究,探讨在其发育过程中是否存在生殖障碍。结果表明:翅果油树花药四囊型,花药壁由表皮、药室内壁、2层中层、绒毡层5层细胞组成,绒毡层为腺质型;小孢子母细胞减数分裂过程中的胞质分裂方式为同时型,小孢子四分体排列方式为四面体型,有时为交叉型或左右对称型;成熟花粉粒为2-细胞型,有3个萌发孔;子房上位,基生胎座,倒生胚珠,双珠被,厚珠心;胚囊发育属于蓼型。其雌、雄配子体发育过程多数正常。     

天女木兰小孢子发生及雄配子体发育的观察

天女木兰是珍稀濒危植物,为给其有效保护措施的制定提供参考,从小孢子发生和雄配子体的发育角度探讨天女木兰濒危原因。研究结果表明,天女木兰花药具有4个小孢子囊,花药壁5～8层。四分体排列方式为平面对称型、四面体型和直线型,其中直线型较少;成熟花粉粒为二细胞型花粉粒;能育花粉率最高达84.9%。通过对天女木兰小孢子发育过程的研究发现,四分体时期有2种不正常类型,说明天女木兰小孢子发育过程中存在异常现象,这是导致天女木兰濒危的原因之一,但不是主要原因。     

棉团铁线莲小孢子发生和雄配子体的形成

采用石蜡切片技术,观察棉团铁线莲小孢子发生和雄配子体的形成过程。结果表明:棉团铁线莲每个花药横切面呈蝶形,具4个花粉囊;小孢子在四分体中的排列以四面体型为主;成熟花粉粒近球形,属2-细胞型,具有3条萌发沟;花粉囊壁由4层细胞构成,即表皮(1层)、药室内壁(1层)、中层(数层)、绒毡层(1层);绒毡层发育属分泌型。     

虎眼万年青小孢子发生与雄配子体发育研究

该文对虎眼万年青的小孢子发生和雄配子体形成进行研究。结果表明:每朵花有6枚雄蕊,每个花药具4个花粉囊,花药壁由表皮、药室内壁、中层和绒毡层组成。小孢子母细胞在减数分裂过程中胞质分裂属连续型,四分体为四面体型与左右对称型两种类型,以四面体型为主。绒毡层发育类型属分泌型,成熟花粉粒属2-细胞型,有1个萌发沟。     

杜松小孢子的发生和雄配子体的发育

利用常规石蜡制片技术,对杜松小孢子发生及雄配子体的发育过程进行观察.杜松的雄球花3月初开始分化.小孢子囊壁一般包括3层细胞:表皮、中层和绒毡层.造孢细胞在3月中旬形成,3月下旬形成小孢子母细胞,4月上旬开始减数分裂,4月中旬形成四分体,4月下旬小孢子从四分体释放出来.5月上旬开始散粉,成熟花粉粒为单核花粉粒.散粉后,胚珠内的花粉萌发出一短的花粉管后休眠,第2年4月份开始分裂形成管细胞、不育细胞和2个精子细胞.小孢子母细胞发育表现出不同步现象,部分小孢子母细胞在发育过程中退化,在小孢子囊内形成空腔.小孢子囊在小孢子叶基部远轴面和叶腋处都有发生,小孢子叶球为复合小孢子叶球.     

赤瓟小孢子发生及雄配子体形成的研究

采用石蜡切片技术,对赤瓟的小孢子发生和雄配子体形成过程进行解剖学研究.赤瓟每个花药具2个花粉囊;减数分裂过程中胞质分裂属同时型,小孢子在四分体中的排列以四面体型为主;成熟花粉粒近球形,属2-细胞型,表面有网状雕纹,具有3条萌发沟;花药壁由4层细胞构成,即表皮(1层)、药室内壁(1层)、中层(数层)、绒毡层(1层);绒毡层发育属分泌型.     

南酸枣大小孢子发生及雌雄配子体发育过程研究

[目的]观察南酸枣雌雄配子的发育过程,初步探究南酸枣雌雄蕊败育的发生原因。[方法]利用石蜡切片观察法研究南酸枣的大小孢子和雌雄配子体的发育过程。[结果](1)南酸枣雌雄异株、单性花,雄花无子房,雌花具退化雄蕊;雄花纵长大于3 mm时,花药成熟,子房纵长达3.5 mm时,胚囊成熟;(2)雄花成熟花药壁共分5层,由外向内为1层表皮、1层药室内壁、2层中层、1层绒毡层,发育形式属基本型;(3)小孢子母细胞分裂形式属同时型,四面体型小孢子四分体,2-细胞型花粉,见3个萌发孔胞质囊;(4)双珠被、厚珠心;胚囊发育类型为蓼型,后期倒转;(5)雌花退化雄蕊的花药壁5层,雌花具左右对称型小孢子四分体,小孢子期绒毡层解体,小孢子解体后花药空囊,药室内壁略纤维状加厚,表皮此时退化;(6)南酸枣雄花从现蕾到散粉约25 d时间,雌花从现蕾到胚囊成熟约24 d时间。[结论]南酸枣雌雄配子发育模式与漆树科大多数种一致;雄花无雌蕊,系花芽发育过程中雌蕊原基退化所致;南酸枣未见退化胚珠,雌花退化雄蕊具正常的小孢子母细胞、异常的小孢子四分体和小孢子,且绒毡层不正常解体,花药空囊,无花粉粒。     

油杉花粉个体发育与传粉过程

应用常规压片法和整体染色透明法对油杉小孢子的发生和雄配子体的发育过程进行观察,研究其传粉生物学特征.结果表明:油杉小孢子母细胞在1月26日-2月5日进行减数分裂,在减数分裂过程中胞质分裂为同时型,四分体排列方式多为左右对称型;小孢子经过连续4次有丝分裂后,于2月底形成5-细胞型的成熟花粉粒,成熟花粉由两个原叶细胞、一个不育细胞、一个精原细胞和一个管细胞组成,其中两个原叶细胞在花粉成熟时已退化;经TCC法检验,花粉生活力为92.6%;3月1日-8日为油杉传粉期,3日-5日为传粉高峰;在传粉期间,胚珠珠孔端无传粉滴产生,珠孔端耳状结构边缘粘附有花粉.虽然花粉母细胞发育表现出不同步现象,产生少数具3个或4个气囊的异形花粉,但从小孢子的发生及雄配子体发育的整个过程看,未见败育或其他异常现象,能形成大量正常的成熟花粉,因此,花粉个体发育不是影响油杉结籽率低的主要因素,而造成油杉球果结籽率低的主要原因可能在于其传粉过程.     

板栗‘遵玉’大小孢子发生及雌雄配子体发育研究

为了系统了解板栗雌雄花发育过程,以板栗优良品种‘遵玉’为试材,对大小孢子及雌雄配子体发生发育进行研究。结果表明:花药壁由外而内分别为表皮、药室内壁、中层及绒毡层(为腺质型),属于基本型。小孢子胞质分离为同时型,四分体为典型的四面体型,少数呈左右对称排列。雄配子体只经过1次有丝分裂,花粉成熟为2-细胞型。雌花胚囊发育为蓼型胚囊,只有1个胚囊母细胞发育成胚囊,四分体呈线性排列,整个发育过程与雌雄花外部特征密切相关。确定观察减数分裂最佳取样时期为:雄花花序长度为10~17 cm,总苞直径为0.9~1.6 cm。‘遵玉’小孢子及雄配子体发生发育不存在异常表现,表明‘遵玉’雄配子体发育正常,花粉可育,可以作为授粉树。     

美国杏李“恐龙蛋”大小孢子及雌雄配子体发育的研究

以美国杏李"恐龙蛋"为材料,系统观察了美国杏李"恐龙蛋"大小孢子及雌雄配子发育,结果表明:2月中旬到2月底,小孢子母细胞形成、细胞减数分裂,四分体渐渐形成,排列疏松。2月底到3月初,形成单核花粉粒。3月初到3月下旬,形成二核花粉粒。     

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.     

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。     

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.