不同品种西梅休眠枝抗寒性研究

以3种西梅的1年生休眠枝为试材,采取人工模拟外界环境的方法对3种西梅休眠枝条进行不同低温(-5~-35℃)的处理,测定其组织含水量和电解质渗透率,应用logistic方程对对各品种西梅休眠枝条的低温半致死温度进行了拟合。结果表明:"女神"的休眠枝自由水/束缚水含量的比值明显高于"红西梅"和"蓝蜜";随着温度的降低电解质渗出率符合"S"型变化曲线,确定半致死温度在-22.8~-25.6℃之间,3个西梅品种枝条抗寒性大小依次为"蓝蜜""红西梅""女神"。     

低温胁迫下紫叶李不同器官渗透性物质变化

该文以紫叶李休眠枝条、芽为试材,进行低温胁迫,对其抗寒生理进行研究。通过电解质渗出率与logisitic方程拟合,得出不同器官半致死温度LT_(50),休眠芽为-11.26℃、枝条为-21.04℃。低温胁迫下,可溶性糖、可溶性蛋白含量在低温胁迫前期增加,达到一定低温呈下降趋势。     

贮藏板栗休眠与萌芽的温度调控

本文研究了板栗贮藏过程中呼吸作用变化和内源激素含量与贮藏温度的关系,确定了板栗的休眠时期,并探讨了通过贮藏温度调控板栗休眠和萌芽的措施。研究结果表明,板栗休眠期长短与贮藏温度有密切关系,在室温（２０℃～２２℃）贮藏条件下板栗的休眠期为２个月左右,在冷藏（０℃～２℃）条件下的休眠期为３个月左右。说明虽然冷藏较室温贮藏能延长板栗的休眠期,但不能完全控制休眠。板栗休眠解除后,在生理上表现为呼吸作用上升和内源激素（ＩＡＡ、ＧＡ３、ＺＲ）含量增加,外观上表现为胚芽萌动生根。冷藏板栗在休眠解除前将贮藏温度降至临界低温（－２℃～－４℃）,可有效地抑制呼吸回升和内源激素的合成,使休眠不被解除,从而在整个贮藏过程中不萌芽。经临界低温贮藏的板栗,仍较好地保持种子活力,出库后品质和萌芽正常,未造成低温伤害。     

流苏树繁育与引种技术

以流苏树(Chionanthus retusus Lindl.etPaxt.)种子为材料,对其进行不同方法的催芽试验。结果表明:1)流苏种子为双休眠性状,种子具有胚根和胚轴双休眠的习性,即胚根需要经过1～2月或更长时间的20～30℃高温阶段才能打破休眠,而胚轴需要3～5℃低温1～3月才能解除休眠。2)流苏种子在高温15～26℃,低温-2～10℃催芽后发芽率高。     

低温胁迫对我国北方地区引种的无花果抗寒性的影响

为给无花果抗寒能力的评价与抗寒品种的选育提供参考依据,以我国北方地区引种的14个无花果品种为研究对象,采用人工低温(0~-20℃)处理对其1年生枝条进行了胁迫试验,并对其相对电导率、可溶性蛋白含量、可溶性糖含量、脯氨酸含量、SOD活性、POD活性和MDA含量进行了测定,还根据相对电导率和对应的低温温度,依据logistic方程,建立了回归模型,对14个无花果品种的抗寒性进行了综合评价。结果表明:依据半致死温度来评价,布兰瑞克、ALMA等品种的抗寒性均较强,-5~-10℃的低温会严重影响参试的大部分品种的生存和生长发育;其SOD和可溶性糖在-10℃时的测定值是反映无花果抵抗和适应低温能力的一个临界值,而可溶性蛋白和POD的临界值是在处理温度为-5℃时的测定值。部分品种的综合抗寒能力的评价结果与其半致死温度的测定结果存在差异,但新早黄、ALMA、金傲芬和紫蕾等品种均具备较好的抗寒潜力。     

几种乔木绿化树种抗寒性比较

本试验以银杏、悬铃木、香花槐、金叶复叶槭和玉兰等5种乔木绿化树种的一年生休眠枝条为试材,通过五个梯度的低温处理(-10℃、-15℃、-20℃、-25℃、-30℃),测定丙二醛、可溶性糖与脯氨酸含量和电导率,研究低温胁迫对这几种乔木绿化树种抗寒性的影响。结果表明:不同树种之间抗寒性存在差异性,5种绿化树种的抗寒性由强到弱的顺序为:悬铃木 > 香花槐 > 玉兰 > 银杏 > 金叶复叶槭。       

低温胁迫下紫叶李休眠枝条内源激素含量与生理指标的变化

以紫叶李1a生休眠枝条为试验材料,测定在低温胁迫下细胞内源激素含量、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性、可溶性蛋白、可溶性糖含量以及相对电导率变化。结果表明:ABA含量、I从含量在-10～-15℃之间迅速增加,之后随着温度降低呈下降趋势;随处理温度降低,SOD活性、可溶性蛋白含量呈双峰曲线变化,在-15、-30℃达到高峰,可溶性糖含量在处理温度前期逐渐升高,在-30℃达到最大值,之后呈下降趋势;相对电导率呈"S"型曲线上升,结合Logistic方程拟合紫叶李低温半致死温度(LT_(50))为-20.17℃。以上结果表明在细胞膜受到伤害之前,植物体内各种保护系统已经启动,提高了组织抗寒性。     

低温胁迫下紫叶李休眠器官活性酶变化

该文以紫叶李休眠枝条、芽为试材,进行低温胁迫,对其抗寒生理进行研究。通过电解质渗出率与logistic方程拟合,得出不同器官半致死温度LT_(50),体眠芽为-11.26℃、枝条为-21.04℃。低温胁迫下,SOD酶活性呈上升-下降-上升-下降趋势变化,到-40℃活性骤然降低。     

种子沙藏管理措施初探

一、低温沙藏的原理 种子在低温（2-5℃）环境中,种子内部的脱落酸等含量显著减少,其抑制种子萌发的作用大大减弱,于是打破了休眠。在这种低温条件下,还能促进产生刺激生长的赤霉素,能促进种子内部酶的活化,使营养物质开始转化。     

解除休眠的水曲柳种子对不同脱水条件的萌发和生理响应

【目的】比较不同脱水条件对解除休眠的水曲柳种子干燥脱水后萌发的影响,并探索在不同条件下脱水过程中种子内部的生理变化,为解除休眠水曲柳种子的再干燥贮藏提供理论和技术依据。【方法】以解除休眠的水曲柳种子为材料,采用单因素设计,比较种子在7种温度(5,10,15,20,25,30,35℃)条件下干燥脱水后的萌发能力,再设计双因素试验,分析脱水温度(常温20℃和低温5℃)、脱水速率(快速和慢速)及其交互作用对干燥脱水后种子萌发的影响,并测定不同脱水条件下种子中抗氧化酶(SOD、POD和CAT)活性,丙二醛(MDA)含量,可溶性糖、可溶性蛋白和淀粉含量,以确定种子细胞膜透性、抗氧化系统酶活性和贮藏物质代谢对不同脱水处理的响应。【结果】经不同温度脱水处理后种子的发芽率和发芽指数呈现随脱水温度的升高先上升后下降的趋势,种子发芽时间则呈现出随脱水温度上升而先下降后上升的趋势。常温(20℃)脱水种子的发芽能力最强,高温(35℃)或者低温(5℃)脱水种子发芽能力较弱。与常温脱水相比,低温脱水种子相对电导率和丙二醛含量显著增加,胚中POD和CAT酶活性显著降低,种子中可溶性糖和淀粉含量无明显变化,但可溶性蛋白含量显著降低。与慢速脱水相比,快速脱水种子相对电导率和丙二醛含量显著增加,胚中SOD和POD酶活性显著降低,种子中可溶性糖和淀粉含量无明显变化,但可溶性蛋白含量显著降低。【结论】解除休眠的水曲柳种子最适的干燥脱水温度是20℃,高温(35℃)或者低温(5℃)脱水会导致种子发芽率和发芽指数下降,发芽时间延长。低温(5℃)或快速脱水后种子细胞膜透性和丙二醛含量显著增加,种子中可溶性蛋白含量和胚中抗氧化酶活性均显著降低,从而引起种子萌发能力下降。胚中的抗氧化酶活性对低温和快速脱水反应不同,POD和CAT对低温脱水更敏感,而SOD则对快速脱水更敏感,SOD、POD和CAT 3种酶必须协同作用才能够维持活性氧自由基处于对细胞无害的较低水平。种子低温或快速脱水过程中脱水保护功能下降主要与蛋白质的变化有关,与可溶性糖和淀粉关系不大。     

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。     

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.