脱毒骏枣幼树叶片叶绿素含量和光合日变化的研究

比较分析了脱毒骏枣幼树与普通骏枣幼树叶片叶绿素含量、光合速率、蒸腾速率、气孔导度、胞间CO2浓度等光合生理指标的日变化。结果表明:脱毒骏枣树叶绿素a与普通骏枣树相比,存在显著差异;脱毒骏枣树与普通骏枣树的光合日变化趋势基本一致,脱毒骏枣树的光合速率、蒸腾速率、气孔导度、胞间CO2浓度总体水平高于普通骏枣树,且在上午光合有效时间内脱毒骏枣树的光合速率、胞间CO2浓度、气孔导度与普通骏枣树呈极显著差异,蒸腾速率呈显著差异。     

不同枣树品种气体交换特性及水分利用效率影响因子研究

以辽宁省朝阳地区8个枣树品种为试验对象,对净光合速率、蒸腾速率、水分利用效率及其影响因子、气体交换特性进行研究,结果表明:不同枣树品种叶片净光合速率、蒸腾速率和水分利用效率日变化均呈"双峰型"曲线。光合速率最大值依次为金丝王枣金丝王蜜枣金丝蜜枣冬枣三星枣大平顶枣山西枣树大铃铛枣;蒸腾速率最大值依次为金丝蜜枣金丝王枣金丝王蜜枣大铃铛枣冬枣=山西枣树三星枣大平顶枣;水分利用效率最大值依次为金丝王枣金丝王蜜枣金丝蜜枣三星枣山西枣树冬枣大平顶枣大铃铛枣。金丝王枣、金丝王蜜枣和金丝蜜枣3个品种水分利用效率较高,更适合朝阳等干旱地区的气候特点。胞间CO2浓度和气孔导度是枣树水分利用效率最直接的影响因子。     

不同新疆核桃品种的光合特性

为了探明新疆主栽核桃品种的光合能力,以新疆8个主栽核桃品种为试材,利用LI-6400便携式光合测定系统测定了不同品种各光合参数的日变化。研究结果表明:扎343和609的净光合速率、气孔导度和蒸腾速率均显著高于其它品种,而新丰和917的各光合参数均显著低于其它品种;各核桃品种的光合速率与气孔导度、蒸腾速率呈正相关,与胞间CO2浓度呈负相关;各品种的叶片净光合速率、气孔导度和蒸腾速率的日变化曲线呈明显的双峰曲线,胞间CO2浓度的日变化曲线表现为不规则的双谷型;各品种的光合"午休"现象是气孔因素和非气孔因素双重影响的结果。     

不同核桃品种光合特性比较研究

用Li-6400便携式光合作用测定系统,对香玲、鲁光、清香、西林3号、西洛3号5个核桃品种的光合生理特性进行了研究。结果表明,5个品种的净光合速率日平均值大小顺序为香玲>鲁光>清香>西林三号>西洛3号。净光合速率日变化、蒸腾速率日变化和气孔导度日变化曲线均呈单峰型和双峰型;不同品种净光合速率与蒸腾速率、气孔导度,蒸腾速率与气孔导度均呈极显著正相关(P<0.01);香玲品种核桃苗叶光补偿点、光饱和点分别为58.997、1 450μmo1·m-2·s-1。     

水分胁迫对3个枣品种光合特性及水分利用率的影响

对朝阳地区常见的3个品种枣苗(大平顶枣、金铃圆枣、三星大枣)2年生嫁接苗进行4个不同的土壤控水处理,测定出3个品种枣苗在不同水分胁迫条件下的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)等光合特性指标,并计算水分利用效率,以探讨水分胁迫对3个枣品种光合特性及水分利用率的影响,结果表明:土壤水分的变化与净光合速率和气孔导度的变化呈正比关系;在重度胁迫条件下,随着胁迫时间的增加,3个枣品种胞间CO2浓度值接近直线上升状态;随干旱胁迫强度加大,蒸腾速率呈下降趋势。三个枣品种抗旱性大小顺序为三星大枣金铃圆枣大平顶枣。     

光合作用对广西5种珍贵乡土树种幼林生长的影响研究

测量及分析红椎等5种广西珍贵乡土树种4年生幼树光合参数和生长特性指标,结果表明:不同树种光合参数差异显著或极显著,各树种净光合速率、气孔导度、胞间CO_2浓度、蒸腾速率范围分别为4.81~12.13 umol·m~(-2)·s~(-1)、0.02~0.08 mol·m~(-2)·s~(-1)、348.55~498.48 umol·mol~(-1)、0.89~1.96 mmol·m~(-2)·s~(-1),净光合速率与气孔导度差异规律相同,胞间CO_2浓度、蒸腾速率差异规律与净光合速率、气孔导度差异规律相近似,表现为红椎各参数值最高,火力楠、红花荷次之,降香黄檀和格木各参数值均较低;除水分利用率外,树高与净光合速率等光合参数均呈极显著正相关,胸径与净光合速率、气孔导度和胞间CO_2浓度呈显著正相关,冠幅与净光合速率和蒸腾速率呈显著正相关;认为各珍贵乡土树种间光合能力差异明显,红椎光合能力强,火力楠、红花荷光合能力次于红椎,格木、降香黄檀光合能力相对最弱。光合能力的强弱直接影响5种珍贵乡土树种生长,光合能力强的树种生长表现好。     

甘肃沿黄灌区30个枣树品种光合及水分利用特性

为给甘肃沿黄灌区枣树良种筛选提供一定的理论依据,以30个4年生引进枣树品种为研究对象,测定并比较了叶片光合生理和植物水分利用效率等指标。结果表明,制干及干鲜兼用枣的骏枣、金谷大枣、金昌1号、灰枣和新郑灰枣的净光合速率和水分利用效率均高;不落酥、马铃枣、尜尜枣和冷白玉等鲜食枣的净光合速率分别为13.89、15.03、12.94和12.67μmol/(m2·s),水分利用效率均高达2.28以上;与净光合速率的相关系数由高到低依次为蒸腾速率、气孔导度、胞间CO2浓度;与气孔导度的相关系数由高到低依次为:胞间CO2浓度、净光合速率、蒸腾速率。单从光合生理和水分利用效率角度考虑,该地区制干及干鲜兼用枣推荐栽种骏枣、金谷大枣、金昌1号、灰枣和新郑灰枣;鲜食枣推荐不落酥、马铃枣、尜尜枣和冷白玉;葫芦枣、磨盘枣和胎里红3种观赏枣均可栽种。     

辽宁核桃品种光合特性研究

以辽宁1号核桃等8种核桃为试材,使用Yaxin-1102便携式光合蒸腾仪,在田间条件下,对核桃光合作用进行了初步研究。结果表明:辽宁1号核桃净光合速率日变化呈双峰型曲线,有明显的光合"午休"现象。不同品种间净光合速率有差异;光合有效辐射、蒸腾速率、气孔导度和叶温均呈单峰型曲线,细胞间隙CO2浓度呈双谷型曲线;核桃净光合速率日变化与叶温极显著正相关,与胞间CO2浓度极显著负相关。     

太空诱变油茶M1代光合特性的研究

为了探明太空诱变油茶M1代的光合生理特性,笔者对油茶苗苗高、地径等生长发育指标及净光合速率、蒸腾速率、气孔导度、胞间CO2浓度、水分利用率等光合日变化参数进行测定和对比分析。结果表明太空诱变油茶M1代的苗高和地径都得到提高,且地径增长达到显著水平;太空诱变油茶M1代的净光合速率日变化为双峰型,在上午11：00时达到首峰,为10.83 mol/m2·s,下午13：00时出现次峰,为6.40 mol/m2·s;胞间CO2浓度变化趋势与净光合速率变化趋势刚好完全相反;蒸腾速率日变化与气孔导度日变化均为单峰型,且趋势完全一致;水分利用率变化趋势与蒸腾速率变化趋势相反。     

高温对20个鸡爪槭品种叶片形态和光合特性的影响

利用自然高温胁迫,研究了高温对20个鸡爪槭品种叶片形态、净光合速率、气孔导度、细胞间CO2浓度、蒸腾速率、水分利用效率和气孔限制值等参数的影响及各参数间的相关性,并以耐热性指标隶属度进行评价。结果表明,20个鸡爪槭品种的耐热性存在明显的差异,d1118和c1116是耐热性最强的2个品种,经过自然高温处理没有出现热害症状,y1106、y1107和x1119耐热性最差,其余品种介于2者之间;多数品种经热处理后净光合速率、气孔导度和蒸腾速率下降显著(P0.05)或极显著(P0.01),水分利用效率提高显著(P0.05),表现出明显的气孔抑制;品种d1118高温处理与对照相比净光合速率、气孔导度和蒸腾速率均显著增加,表现出极强的高温适应性;品种j1123高温条件下净光合速率下降,但仍保持较高的气孔导度和胞间CO2浓度,属于典型的非气孔抑制;高温引起的叶片热害症状与光合参数间不存在显著的相关性,但与蒸腾速率的相对变化值有显著(P0.05)的负相关。     

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.     

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。     

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.