四唑染色法测定毛竹种子生活力的研究

采用染色全过程观察和正交试验方法研究了TTC浓度、温度和染色时间对毛竹种子生活力的影响,探讨毛竹种子生活力测定的最佳条件。结果表明:四唑染色法能够很好地检测毛竹种子生活力水平,估测种子的潜在发芽能力。TTC浓度、温度和染色时间在生活力测定中存在一定的线性关系。试验表明,25℃下浸种48 h待种子完全吸涨后,于30~35℃黑暗条件下、TTC浓度0.5%,染色3~4 h为毛竹种子生活力测定的最佳条件。     

水青树种子的需光萌发特性

对水青树Tetarcention sinense Oliv种子休眠和萌发的生理特性进行了研究.结果表明:水青树种子属典型的需光性种子,在黑暗条件和恒温中,新采集的种子完全不能萌发,在变温中也仅有9.75%~17.00%的萌发率,只有在萌发过程中给予1 000 lx光照强度和8 h光周期才能充分萌发,萌发率可高达64.75%~85.00%;种子的含水状况对光的效应有一定的影响,种子须浸种8 h,其含水量达饱和状态时,种子萌发快而整齐;用赤霉素溶液处理可以在很大程度上代替种子萌发时对光的需要,其适宜的质量分数为12×10-4;种子萌发的最适宜温度为光照下25℃恒温,其次是20℃恒温和25℃日/15℃夜、30℃日/15℃夜、30℃日/20℃夜变温.     

温度老化和激素处理对鹅观草种子萌发的影响

以鹅观草种子为研究对象,探讨了不同的老化温度和激素处理对鹅观草种子萌发的影响。以蒸馏水处理为对照,在3种不同浓度的ABA、NAA和GA以及3个温度(30℃、40℃、50℃)下对种子进行了处理,观察种子发芽率。研究结果表明:温度老化处理下种子萌发率随着温度的升高而降低,30℃下的萌发率最佳,50℃发芽率最低;ABA促进了种子的休眠,降低了种子的发芽速率,10mmol/LABA处理下的种子萌发率显著低于其他浓度的萌发率,其他各浓度间无显著差别;GA打破了种子休眠,3mmol/L时萌发速度最快,高浓度GA处理下的种子萌发率显著降低;NAA显著降低了鹅观草的萌发速度和萌发率,高浓度的NAA对萌发起到了抑制作用。     

浸种温度与时间对毛竹种子发芽的影响研究

研究了不同浸种温度、浸种时间和种子是否去芒对毛竹种子萌发的影响。结果表明:毛竹种子6 d基本能完成吸胀过程;初始浸种温度60℃浸种6 d,毛竹种子发芽率最高;在最佳浸种温度下,去芒与否对毛竹种子萌发率的影响差异不显著;80℃的浸种水温显著降低毛竹种子的发芽率。     

不同温度对顶果木种子萌发的影响

文章为研究不同温度条件下种子萌发的情况,将顶果木种子放在不同温度条件下进行萌发。结果表明,25℃时种子的发芽率和萌发指数已达到较高水平,分别为84%和19.14;30℃条件下种子具有最高的发芽率、萌发指数和较高的发芽势,分别为89%、21.88和83%,且萌发期间,种子对营养物质的转换能力较强,幼苗的抗逆性不断增强,完全能够达到早苗、齐苗和壮苗的要求。说明顶果木种子萌发的适宜温度为25~30℃,最适温度为30℃。     

香果树种子休眠和萌发的生理特性

为了解决香果树Emmenopterys henryi种子萌发困难的问题,使用不同的光照条件较系统地研究了香果树种子休眠和萌发的生理特性.结果表明:香果树种子属典型的光敏感性种子,在黑暗中无论恒温或变温条件下均完全不能萌发;整个萌发过程需1 000 lx光照强度和每天照光16 h;在光照条件下适宜的萌发温度为20℃、25℃恒温,其次是30℃恒温和30℃(日)、20℃(夜)变温.     

毛竹种子萌发及幼苗生长对环境条件的可塑性响应

以毛竹种子、实生苗为研究对象,分析了其种子在强声波处理后,高温、干旱胁迫对生物量累积分配和异速生长特征等行为的影响。结果表明:频率1 000 Hz、强度100 db的机械声波和自主研发的新型海藻肥营养液对毛竹种子的萌发率有明显的效果;机械声波的使用可以提高高温胁迫下的种子萌发率,种子萌发数量、萌发胁迫指数和萌发持续时间表明其作用比施用主成分为海藻肥的营养液更显著。声波预处理种子后,对其萌发的幼苗的生长亦出现后延的影响:正常环境(25℃)下,声波处理的萌发苗的生长更倾向于地上部的生长,而营养液处理的萌发苗有向地下部分配的倾向性;35~40℃的环境温度将明显抑制毛竹幼苗的生长,对声波预处理的萌发苗有明显的负作用,其幼苗侧根数、地上高和根长数据都显著下降,而营养液预处理对根系有保护作用;干旱与高温的作用机理有明显差异,毛竹幼苗表型可塑性表现亦不同,生长发育过程中对水分比较敏感,声波预处理的幼苗纵向地发育根系,而干旱对照更倾向于横向平面发展根系;营养液在干旱胁迫下,对根系仍有保护作用,这与高温胁迫相似。     

温度对薄壳山核桃种子萌发的影响及其机制初探

将薄壳山核桃的完整种子与去壳种子在不同温度条件下进行发芽试验,并测定了温度对淀粉酶活性的影响,菜豆素(淀粉酶抑制剂)对完整种子萌发的影响,以及不同温度对种子萌发初期中,淀粉、可溶性糖、粗脂肪、可溶性蛋白和游离氨基酸变化的影响。结果表明:薄壳山核桃种子在30、35℃条件下,种子萌发率分别为84%、82%,显著高于15、25和40℃3个温度下的情况,且所需的萌发时间较15、25℃条件下更短;因此薄壳山核桃种子适宜的萌发温度为30~35℃的高温条件,而超过该温度区间容易对种子造成伤害。同时,生理研究的结果显示,15~30℃时,温度越高,薄壳山核桃种子淀粉酶活力也越高,而淀粉酶活性抑制剂能够显著降低薄壳山核桃种子在30℃中的萌发率,这表明在一定温度范围内,温度变化可改变淀粉酶活性,从而调控薄壳山核桃种子萌发;同时,其它生理指标测定表明,糖类的代谢与蛋白质的代谢在种仁响应温度变化的过程中具有重要的作用。     

PEG模拟干旱对毛竹种子萌发及生长生理特性的影响

[目的]通过比较不同程度干旱胁迫对毛竹种子萌发及生长生理的影响,探究毛竹种子萌发期对水分胁迫的耐受机理,为毛竹的水分管理提供科学依据。[方法]以毛竹种子为试验材料,采用培养皿滤纸萌发的方法研究不同浓度(0%、5%、10%、15%、20%、25%) PEG-6000溶液对其种子萌发、生长、渗透调节物质、抗氧化酶活性的影响。并对种子萌发率、胚根和胚芽的生长量与PEG胁迫浓度间进行回归分析。[结果](1)对照组(CK)和5%处理组在第4天开始发芽,其余各处理组的发芽起始时间随处理浓度的升高逐渐延迟,25%处理组不发芽。(2)最终发芽率、发芽势、发芽指数、活力指数、胚根长度、胚芽长度随PEG浓度的升高呈现先增大后减小的趋势,且均在5%浓度达到最大值。干旱胁迫下毛竹种子发芽率日变化曲线中对照组和5%处理组间存在唯一交叉点。毛竹种子在PEG胁迫下发芽率的临界值和极限值分别为14. 49%和19. 27%。(3)胚根和胚芽最终长度均在5%浓度时达到最大值,其后随着浓度的升高而减小,处理间差异显著(P 0. 05)。对照组和5%处理组的胚根平均长度日变化曲线存在交叉点。PEG胁迫下胚根生长的临界值和极限值分别为20. 43和23. 01%。(4)胚根中SOD、POD、CAT的活性均随PEG浓度的升高呈先上升后下降的趋势,且分别在5%、10%、10%浓度时达到最大值。(5) MDA和可溶性蛋白含量随PEG浓度的升高而持续升高,但低浓度(0%10%)时MDA含量差异不显著。[结论]低浓度干旱胁迫抑制发芽前期毛竹种子萌发以及胚根的形成,但显著提高毛竹种子的最终发芽率并且促进胚根后期的生长;而高浓度PEG干旱胁迫延迟毛竹发芽,抑制整个发芽时期的发芽率以及胚根、胚芽的生长; PEG浓度高于15%的干旱胁迫使毛竹的抗氧化酶系统发生紊乱,并对组织膜系统造成显著伤害。     

柳兰种子萌发条件研究

分别采用光照和黑暗处理,在系列温度梯度下观察柳兰种子萌发情况,结果表明：光照和黑暗处理情况下柳兰种子均可萌发。适宜柳兰种子萌发的温度为15-20℃。     

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。