贮藏温度和时间对木棉与美丽异木棉种子活力的影响

利用木棉 Bombax ceiba 和美丽异木棉Chorisia speciosa混合种子,在0、4、和8℃条件下贮藏135d,每隔45 d测定一次种子场圃发芽率和活力指标,用2,3,5-三苯基氯化四氮唑法(TTC法)测定种子的初始和贮藏135 d的生活力。结果如下:木棉种子在相同贮藏温度条件下,随贮藏时间的延长,发芽率、发芽势、活力指数存在显著差异(P<0.05),贮藏温度和贮藏时间有极显著的交互作用,种子活力逐渐下降,贮藏135 d后种子发芽率在8.33%以下,基本失去发芽能力;美丽异木棉种子在不同温度下,随着贮藏时间延长,发芽率、发芽势、活力指数没有显著差异,贮藏温度和贮藏时间没有显著的交互作用,种子发芽率为新鲜种子发芽率的67.46%以上;利用TTC染色法(1.0%浓度)能反映出木棉的种子生活力;木棉种子0℃贮藏90 d发芽率好于4和8℃,可在生产中推广应用TTC染色法检测木棉的种子生活力;美丽异木棉种子0、4、8℃贮藏135 d的发芽率差异很小,0℃贮藏发芽率和活力指数较优。     

不同贮藏条件对米老排种子含水率和萌发特性的影响

通过设置真空铝箔袋、瓦罐和布袋3种封装材料和-20、-5、4、10℃和室温5种贮藏温度等15个组合,研究不同贮藏条件对贮藏6个月米老排(Mytilaria laosensis Lecomte)种子含水率和萌发特性的影响,以筛选最佳种子贮藏方案。研究结果表明,不同封装材料和贮藏温度对米老排种子含水率和萌发特性具有显著影响。布袋封装时,5种贮藏温度的种子含水率平均为9.61%,发芽率平均为21.5%;瓦罐封装时,种子含水率为11.48%,发芽率为15.8%;而真空铝箔袋封装时,种子含水率高达16.90%,发芽率基本为0。对于贮藏温度,4℃和10℃贮藏的种子发芽效果较好,-20℃和-5℃的效果一般,而常温贮藏的效果最差。不同封装材料和贮藏温度对种子含水率和种子萌发特性具有一定的交互作用,采用布袋或瓦罐封装在4℃和10℃进行冷藏的贮藏条件最佳,其贮藏6个月的种子发芽率约为30%,为新鲜种子发芽率的40%左右。种子含水率与种子发芽率具有较强的关联,其关系大致呈尖峰状分布,适宜的种子含水率有利于保持种子活力,从而促进种子发芽。综合分析,采用布袋或瓦罐封装在4℃和10℃进行冷藏的贮藏条件最佳,其贮藏效果最好。     

温度和光照对多花黄精种子萌发的影响

为了解多花黄精种子的萌发特性,探索其种子萌发的最适宜条件,以年珠林场收集的多花黄精种子为研究材料,开展其种子形态测定以及温度和光照对其种子萌发特性影响的研究。结果表明：温度对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响达到显著水平;在10℃～35℃范围内,随着温度的升高,种子的发芽率、发芽势和发芽指数均呈现先增加后减小的趋势,而平均发芽时间则呈现先减小后增加的趋势;当温度为25℃时,种子发芽率、发芽势和发芽指数最高,分别为93.4%、70.1%和48.5,平均发芽时间最低为11.4 d。光照对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响不显著。试验结果为多花黄精栽培育苗提供技术支持和理论支撑。     

发芽基质对垂柳种子发芽能力的影响

以当年生垂柳(Salix babylonica)种子为材料,通过不同的贮藏温度及发芽基质条件对种子进行研究,结果表明:柳树种子7d仍具有较高的生活力,贮藏温度显著影响种子发芽能力,适宜的低温贮藏条件有利于保持种子生命力,综合发芽率和幼苗生长2个方面,-5℃与-4℃的贮藏温度对柳树种子保存最为有利;发芽基质对垂柳种子发芽率具有显著的影响,滤纸发芽床和琼脂培养基显著好于人工基质,发芽从高到低的基质排序分别是:沙子>草炭>土壤。     

箭根薯种子发芽试验

对箭根薯种子的室内发芽情况进行了试验.结果表明:在黑暗条件下,种子不能萌发;光照强度和光照时间对种子发芽率没有显著影响;每天光照14h,在15～35℃范围内,温度对发芽率无显著影响,但不同温度下发芽速率却有显著差异;在自然状况下风干的种子,种子含水率不同,其发芽率无明显差异;种子在4℃下贮藏1a,其发芽率不会下降,在-18℃下贮藏半年,其发芽率不会明显下降,贮藏半年以上,则下降明显.     

贮藏温度对枫香种子耐贮性的影响

[目的]以枫香种子为试材,研究不同贮藏温度下种子活力随时间的变化规律,为枫香种子的贮藏方法提供理论依据。[方法]将枫香种子阴干至含水量为10.54%,然后分别贮藏于室温(25±2)℃、4℃、-20℃和-70℃的温度条件下,于贮藏0、60、180、300、360、520、730 d分别测定种子的丙二醛含量和相对电导率,并将种子于室内播种,测定发芽势、发芽率及播种1个月后萌发幼苗的苗高和根长。[结果]随着贮藏时间的延长,4种温度下种子的发芽率、发芽势、幼苗苗高与根长均逐渐降低,丙二醛含量和相对电导率逐渐升高;贮藏至360 d时,4种温度均能较好地保持种子活力,相互之间差异不明显;至730 d时,4℃、-20℃和-70℃的贮藏效果明显优于室温,-70℃的贮藏效果最佳。[结论]枫香种子在含水量10.54%时,若贮藏时间在360d以内,则室温贮藏即可有效保持种子活力;若贮藏时间进一步延长,则需要采用低温进行贮藏;贮藏730d时,4℃、-20℃和-70℃均可有效保持种子活力,其中,-70℃的贮藏效果最佳。     

温度和赤霉素对胭脂花种子萌发的影响

该文研究了温度和赤霉素处理对胭脂花种子萌发的影响。结果表明:胭脂花种子在15~25℃均有较高发芽率,且在20℃有最高的发芽率、发芽势和发芽指数;30℃的种子发芽率显著低于其它各组。赤霉素能促进胭脂花种子萌发,但各浓度处理间差异不显著;赤霉素浓度为250mg/L时的种子发芽率、发芽势最高,而处理浓度为350mg/L时的种子发芽指数最高。综合认为:在胭脂花播种繁殖时,可采用25℃培养条件下250~350mg/L的赤霉素处理或单用20℃温度对种子进行预处理,促进种子萌发。     

贮藏温度和贮藏时间对垂柳种子生活力的影响

以成熟的垂柳种子为材料,测定了不同贮藏温度和不同贮藏时间下垂柳种子发芽率、发芽势、活力指数等生活力指标的变化,以探索贮藏温度和贮藏时间对垂柳种子生活力的影响。结果表明:适当的低温-10℃、-5℃、4℃可以延缓垂柳种子的劣变,延长其贮藏时间;常温20℃与极低温-20℃条件下会降低种子的生活力,表现为活力指数降低;随贮藏天数的增加,发芽率、发芽势、发芽指数表现出先升高后降低的趋势,发芽速则是先降低后升高。常温20℃贮藏7天种子发芽率显著下降,在-5℃贮藏3天的条件下种子生活力最强,可应用于垂柳种子萌发及人工种苗培育的实践中。     

贮藏温度对川滇桤木种子发芽能力的影响

3种不同贮藏温度下川滇桤木种子发芽试验的结果表明:川滇桤木种子采收后冷藏(4±1℃)贮藏是最适宜的贮藏方法,对种子发芽能力的影响最小;冷冻(- 18±1℃)贮藏的种子发芽率与冷藏的种子没有显著差异,但发芽势随着贮藏时间的推移与冷藏的种子存在显著差异;常温贮藏下的种子发芽率与冷藏的种子差异显著,发芽势和高峰值差异极显著。用冷藏和冷冻的方法贮藏种子可以较好的保持其发芽率,但贮藏时间过长种子会出现一定程度的腐坏霉变。     

香果树种子贮藏试验

本文通过香果树种子沙藏、5℃低温贮藏、-5°冷冻贮藏、对照(CK)贮藏试验,结果显示在5℃低温环境中贮藏,种子发芽率最高,达66.8%;不同贮藏方式对香果树种子发芽势和种子发芽时间有明显影响。种子贮藏时间试验表明贮藏时间对香果树种子萌发影响较大,在5℃低温贮藏下种子可长期贮藏并且能够保持较高发芽能力。     

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.     

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。     

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.     

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.     

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.