脱落酸对低温胁迫下水曲柳幼苗叶片抗寒生理指标的影响

以3a生盆栽水曲柳幼苗为试材,喷施不同浓度的脱落酸,喷后第1d、5d、10d和15d分别采集带叶枝条测定常温和低温胁迫后幼苗叶片质膜相对透性、SOD、POD、可溶性糖含量、水溶性蛋白质含量的变化。进行自然条件下季节性低温处理试验,以验证人工低温试验中所得结论。研究结果表明：10mg／L浓度的ABA增强水曲柳幼苗抗寒性的作用效果最好,能显著降低电导率,显著提高蛋白质含量、SOD活性、POD活性。但对可溶性糖含量的影响无明显变化。30mg／L浓度的ABA预处理有一定的作用效果,但高浓度的60mg／LABA预处理对于增强水曲柳幼苗抗寒性出现了一定的抑制作用。在自然低温条件下,10mg／L浓度的ABA预处理增强水曲柳幼苗抗寒性的作用效果最好,高浓度的无显著作用。     

采后NaClO水浴处理对板栗沙藏效果的影响

以'燕昌'板栗为试材,研究了采后不同浓度NaClO(100、500、1 000 mg·L-1)水浴处理对板栗沙藏效果的影响.研究表明:500 mg·L-1NaClO水浴处理有利于降低板栗在沙藏期间(30 ～150 d)的淀粉水解,有利于保持沙藏后期的淀粉含量.1 000 mg·L-1NaClO水浴处理抑制了蛋白质的降解,其它处理与对照没有差异.水浴处理促进了板栗在处理期间的乙醇积累,在沙藏过程中乙醇逐渐消失并且与对照没有差异.NaClO水浴处理对抑制沙藏板栗的发芽和腐烂有明显作用,经150 d沙藏,500 mg·L-1处理的发芽率和腐烂率均为2%,1 000 mg·L-1处理的均为0.500、1 000 mg·L-1NaClO水浴处理有利于提高沙藏板栗的质量.     

赤霉素对邓恩桉嫁接种子园花蕾生长的影响

以邓恩桉嫁接种子园为研究材料,分别以赤霉素0、500、1000、1500 mg·L-1进行叶面喷施,研究赤霉素处理对花蕾直径生长、花蕾保存率,叶片叶绿素、氨基酸、蛋白质、可溶性糖含量的影响。结果表明:赤霉素处理后花蕾保存率、氨基酸含量、可溶性糖含量显著高于对照,花蕾直径生长量第2次观测值显著大于对照,可溶性蛋白质含量第1、2次观测值显著高于对照;随着时间的延长,叶绿素含量呈先升高后下降趋势,氨基酸、可溶性蛋白质含量分别呈极显著、显著下降趋势,可溶性糖含量呈显著上升趋势。表明赤霉素处理对提高花蕾直径生长量、花蕾保存率、叶绿素、氨基酸、可溶性蛋白质、可溶性糖含量效果明显,其中以赤霉素1000 mg·L-1处理效果最好。     

次氯酸钠处理对板栗货架期萌芽与激素含量变化的影响

以燕山板栗为试材,研究0℃下冷藏板栗出库后用不同浓度次氯酸钠(NaOCl)溶液浸泡处理对板栗货架期发芽与激素含量的影响.5 000 mg·L-1 NaOCl处理可完全抑制板栗发芽;1 000、3 000 mg·L-1 NaOCl处理对发芽没有明显的抑制作用,板栗发芽率仍较高,与对照没有显著差异.1 000、3 000 mg·L-1NaOCl处理可降低板栗的呼吸强度,5 000 mg·L-1 NaOCl处理后板栗在货架期第3天呼吸强度显著升高,随后逐渐降低.NaOCl浸泡处理对板栗4种主要内源激素的影响在一定程度上与NaOCl浓度相关.与对照相比,1 000 mg·L-1 NaOCl使板栗ABA、GA3、IAA含量降低,并推迟IAA和ZR含量峰值出现的时间;3 000 mg·L-1NaOCl处理使板栗ABA含量降低,使其他激素水平升高;5 000 mg·L-1NaOCl处理使板栗各激素水平有不同程度升高.NaOCl处理降低了板栗货架期前期ABA/GA3、ABA/IAA比值,并推迟了其峰值出现时间;1 000、3 000 mg·L-1 NaOCl处理还降低了ABA/ZR比值,而5 000 mg·L-1 NaOCl处理使板栗ABA/ZR比值升高.板栗货架期发芽主要受ABA含量调控.     

水浴处理板栗MA贮藏期间抗氧化酶活性变化规律

以北京昌平的燕昌板栗为试验材料,研究经不同水浴处理后,板栗MA(Modify atmosphere)贮藏期间抗氧化酶活性的变化规律。结果表明:NaClO水浴处理对板栗内PPO、外PPO活性有抑制作用,除1 000 mg.L-1NaClO处理使板栗外PPO活性一直高于对照外,其余各处理的PPO活性在整个贮藏期间一直低于对照;POD活性的变化规律与PPO活性的变化规律类似,但在贮藏180 d时,NaClO处理的内POD活性高于对照,其中1 000 mg.L-1NaClO处理的内POD活性与对照存在显著差异;100 mg.L-1NaClO和500 mg.L-1NaClO处理使板栗SOD活性升高,而1 000 mg.L-1NaClO处理则使SOD活性降低;NaClO处理板栗提高了板栗的CAT活性,但CAT活性变化趋势与对照相同。     

亚硫酸氢钠对蚕豆光合生产和蛋白含量的影响

在蚕豆(Vicia fabaL.)灌浆期对其叶面喷施50 mg.L-1和100 mg.L-1的亚硫酸氢钠溶液,结果表明:两种浓度的亚硫酸氢钠均可提高叶片净光合速率,增加籽粒产量,其中50 mg.L-1的促进效果明显。同时研究表明,亚硫酸氢钠虽然可以增加籽粒产量,但却降低了籽粒的蛋白质含量,其中100mg.L-1处理后的降低幅度较大。此外,试验还测定了各处理组的叶绿素含量,结果表明,亚硫酸氢钠对促进叶绿素含量增加与光合产量增加呈正相关。     

硒肥对老鹰茶叶绿素含量影响研究

以老鹰茶一年生扦插苗为研究对象,采用盆栽施肥试验,研究了不同硒肥处理(硒浓度分别为0mg·L~(-1)(CK)、50mg·L~(-1)(T1)、100mg·L~(-1)(T2)、200mg·L~(-1)(T3)、300 mg·L~(-1)(T4)、400 mg·L~(-1)(T5))对老鹰茶幼苗叶绿素含量的影响。结果显示:经硒处理后,叶片叶绿素总量、叶绿素a、叶绿素b含量均增加,变化趋势呈先增后减,在T3处理时达到最大值,且显著高于对照,此时叶绿素b的增幅大于叶绿素a。     

不同水杨酸处理方式对喜树幼苗铝胁迫的缓解效应

通过根施和叶面喷施水杨酸(SA)的2种预处理方式,研究水培条件下水杨酸对喜树幼苗铝毒害的缓解效应.结果表明:1 000 mg/L的AlCl3处理降低了喜树幼苗的单株鲜质量、主根长和侧根数量,叶绿素含量和根系活力也显著下降,细胞膜透性增加,说明喜树幼苗受到了一定程度的铝胁迫.铝处理下经2种不同方式水杨酸预处理的喜树幼苗在铝处理8d和16 d后,都不同程度地提高了喜树幼苗的鲜质量、叶绿素含量、根系活力,降低了相对电导率,提高了喜树碱的含量,说明水杨酸能够有效缓解铝对喜树幼苗的伤害.从处理效果上看,50 mg/L SA叶面喷洒处理效果最好,25 mg/L SA的根施处理抑制了茎的伸长,但促进了侧根的形成及喜树碱的合成.     

稀土对巨尾桉苗木生长的影响及生理效应研究

用0、50、100、200、300mg/L的稀土处理巨尾桉幼苗,以探讨其对巨尾桉苗木生长的影响及生理效应.结果表明稀土能促进苗高和地径的生长.提高根系活力,增加叶片气孔密度和栅栏细胞密度,提高叶片N、P、K以及蛋白质含量.提高苗木叶绿素含量和净光合速率.     

NaCl胁迫对毛竹幼苗叶绿素荧光特性及生理指标的影响

以毛竹幼苗为材料,通过测定在不同浓度(0、50、100、150 mmol.L-1)NaCl胁迫条件下的幼苗生长、叶绿素荧光参数及生理指标的影响,结果表明:随着NaCl浓度的增加,毛竹幼苗的植株生长量、苗高生长量呈显著下降的趋势;与对照相比,NaCl胁迫条件下,毛竹幼苗叶片的PSⅡ最大光化学效率(Fv/Fm)显著降低,PSⅡ电子传递量子效率(ΦPSⅡ)显著降低。低NaCl浓度(50 mmol.L-1)胁迫下,光化学淬灭(qP)与对照无显著差异,高NaCl浓度(100~150 mmol.L-1)胁迫下,qP显著下降。非光化学淬灭(NPQ)无显著差异;毛竹叶片的叶绿素含量在低NaCl浓度胁迫下,与对照无显著差异,高NaCl浓度胁迫下,显著降低;各个NaCl浓度处理下的毛竹叶片脯氨酸含量均有显著差异。     

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.     

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.     

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。