木材心材形成原因和机理研究进展

本文介绍了木材心材和边材的差异,着重分析了木材边材转变为心材、心材形成的原因和机理,有树体自身生长需求、促进物质调控、真菌和细菌侵入、林木经营措施、种植地立条件、自身遗传因素调控等。同时介绍了国内外人工促进心材形成的方法,对人工促进木材心材形成提出了建议,为提高木材培育效率提供理论基础。     

影响心材形成的因素与机理及人工诱导硬木心材研究进展

心材一般具有密度大、耐腐蚀、材色美观等优点，被广泛用于医药、香料等领域，有些被作为高档家具的名贵用材，具有广阔的市场前景。分析了影响木材心材及伪心材形成的因素；重点阐述心材形成机理，包括程序性细胞死亡、特定酶活性增强、防御机制启动、激素平衡打破等；同时综述了植物内外源激素调节、真菌胁迫、外源气体胁迫等人工诱导硬木心材形成的方法；并讨论当前研究存在的不足并展望未来研究方向，以期对后续研究提供参考。     

湿心材研究进展

笔者对国内外湿心材研究进展作了全面的概述,并提出研究中存在的问题,在此基础上提出了我国杨树湿心材未来研究方向。国外对于湿心材研究对象包括多种树种,研究的内容涉及湿心材的形成、湿心材中的细菌、液体和气体、湿心材的特征和湿心材检测等方面。我国湿心材研究的广度和深度与国外存在一定差距,杨树是我国主要速生造林树种之一,今后应该加强杨树湿心材病原、抗性育种和防治等方面的研究。     

降香黄檀人工促进心材研究进展

降香黄檀(Dalbergia odorifera)心材自然生长条件下成材期较长,通过人工干预促进心材生长将有可能大大缩短这一过程。对木材的心材的形成条件及人工干预降香黄檀心材形成的方法逆境胁迫、生长调节剂干预和真菌菌液作用等进行了总结分析。人工干预方法对降香黄檀心材形成均具有一定程度的促进作用,且较易实施,但由于其心材形成时间较长,取样较为困难,且心材挥发油的标准体系不够完善等因素,目前尚无确切成熟的方法。     

3种生长调节剂对檀香生长及心材形成的对比研究

为研究植物生长调节剂对幼龄檀香生长及心材形成的影响,以6年生幼龄檀香(Santalum album)为试验材料,采用树体注入的方法,比较研究3种浓度(2g/L、4g/L、6g/L)植物生长调节剂乙烯利(ETH)、茉莉酸(JA)和甲基紫精(MV)对其生长和心材形成的影响。结果表明,试验1年后,不同浓度、不同生长调节剂对6年生檀香的树高、胸径生长与CK组差异不大;但能促进檀香形成深褐色的心材。以浓度2 g/L、6 g/L乙烯利和甲基紫精处理最佳;心材直径2~3 cm,茉莉酸处理不利于心材形成。研究结果初步表明檀香不仅能在热带地区三亚生长,注射生长调节剂也能促成心材的形成。     

国外对杨树湿心材的研究

杨树是我国主要速生造林树种之一。杨树的利用对我国林业和林产工业的发展有重要影响。湿心材是树木生长中的一种反常现象,在杨树中表现甚为突出,是杨树加工利用中的一大难题。国外对湿心材的研究于上世纪初即已开始,已取得许多研究成果。本文扼要介绍国外研究的进展和一些重要观点,涉及湿心材的形成,湿心材中的细菌、气体和水分,湿心材的酸度、材色、力学强度、渗透性和湿心材对干燥、人造板生产和刨削等工艺过程的影响。     

乙烯利诱导形成降香黄檀心材挥发油的GC-MS分析

为了加快降香黄檀心材形成的速度,采用乙烯利诱导降香黄檀形成心材,水蒸气蒸馏法提取心材的挥发油,利用GC-MS对提取的挥发油进行化学成分分析。结果表明:从挥发油中,鉴别出8种化学成分,含量最高的是橙花叔醇(39.06%)。说明乙烯利诱导能够促进降香黄檀心材形成,是一种值得深入研究和推广使用的方法。     

降香黄檀心材和边材内生真菌多样性

【目的】研究降香黄檀心材和边材中真菌群落结构和多样性及其与木材内环境因子的关系,为降香黄檀内生真菌价值评价和资源利用提供依据,为指导降香黄檀人工促进心材形成提供参考。【方法】采用高通量测序技术,结合木材理化性质,研究降香黄檀心材和边材内生真菌的群落结构和多样性,并采用方差分析、冗余分析等手段分析其与降香黄檀内环境因子的关系。【结果】经过高通量测序,共获得2 193 336条序列,碱基总数为761 438 850 bp,有效序列平均长度为385 bp。得到3 621个OTUs,分属26纲67目116科167属186种。纲水平上,心材内生真菌优势菌群为伞菌纲、粪壳菌纲和散囊菌纲,边材内生真菌优势菌群为粪壳菌纲、座囊菌纲、伞菌纲、地舌菌纲和银耳纲;属水平上,心材内生真菌优势菌群为暗枝顶孢壳属、镰刀菌属、孢子丝菌属、黑酵母样真菌属和球托霉属,边材内生真菌优势菌群为镰刀菌属、毛色二孢属、枝孢属、念珠菌属、德巴利酵母属和木霉属;种水平上,心材内生真菌优势菌群为孢子丝菌环境种、卵形孢球托霉菌和尖孢镰刀菌,边材内生真菌优势菌群为可可毛色二孢菌、酵母菌和镰刀菌。方差分析、冗余分析等结果表明,p H、灰分和钾元素与降香黄檀内生真菌属水平的群落结构呈负相关,热水抽提物、镁和钙元素与大部分属真菌群落呈正相关,与少量属真菌群落呈负相关。含水量、热水抽提物、矿质元素钙和镁与多样性指数Chaol、Shannon和Simpson指数呈正相关,p H、灰分和钾元素与其呈负相关。【结论】降香黄檀心材和边材含有丰富的内生真菌群落,群落结构丰度和多样性均为心材大于边材。引起心材和边材内生真菌群落结构性差异的主要木材内环境因子为p H、灰分和矿质元素钾,引起多样性差异的主要木材内环境因子为p H、含水率、矿质元素钙和钾,且含水平影响最大。     

树木木质部细胞凋亡及心材形成机理研究进展

概述有关木纤维、管状分子与薄壁细胞等木质部细胞凋亡和心材形成方面的研究成果,探讨木质部细胞凋亡与心材形成之间的信号通路及调控机理,并基于当前研究现状,提出几点建议。     

加压因素对杨木单板压缩率和回弹率的影响

以速生杨木的边/心材单板为研究对象,对其进行水热密实化处理,通过单因素试验方法,分别研究了加压温度和加压压力对杨木边/心材单板的压缩率、气干24和48 h的厚度回弹率的影响,初步探讨了各个因素的作用机理.研究发现:各因素水平下,杨木边/心材单板的压缩率和厚度回弹率均呈现出一定的规律性,心材单板的压缩率高于边材单板,但厚度回弹率低于边材单板,且各因素的作用机理有所差异.边/心材单板水热密实化处理的较佳条件均为:加压温度150℃,加压压力5 MPa.     

Essential oil content and composition of Indian sandalwood (Santalum album) in Sri Lanka

Santalum album (Indian Sandalwood) is found in the mountainous regions of the intermediate zone of Sri Lanka. Few studies have been conducted on sandalwood ecology in this region, and ours is the first recorded study of essential oil content and chemical composition of heartwood. We harvested two trees with State permission and took crosssections for analysis. We demonstrated a difference in the heartwood formation and oil yield of the trees. The composition of the oil was found to be consistent between trees and along the trunk of the tree. Main aromatic compounds were santalols and other compounds are recorded in lesser quantities. Results of this study comply with the other published work on sandalwood elsewhere. This initial study on S. album in Sri Lanka provided promising results for the future of sandalwood agro- forestry.     

城市绿色空间对居民心理健康影响研究综述

随着经济增长和城市化的推进,城市居民在收入水平提升后,对于居住品质尤其是绿色健康生活的需求日益增加。已有系列研究证实了城市绿色空间与居民心理健康的正相关关系,但其因果关系特别是影响机制的相关研究尚不充分。基于此,文中综合不同学科的研究,概述了城市绿色空间与居民心理健康关系的相关结论,总结出可能的影响机制——即以情绪、压力、社会交往和邻里满意度为中介因素;从研究的主要对象和具体方法2个方面对国内外有关城市绿色空间与居民心理健康关系的研究进行了分析对比;从精准化的信息采集、系统化的实证研究、多学科的综合研究3个方面对下一步研究提出具体建议。     

黑木相思株内木材基本材性变化与树龄关系的研究

对不同树龄和径向位置黑木相思木材的物理和主要力学性质测定研究表明:黑木相思株内边材、心材密度和主要力学性质随着树龄的增大而增大,径向和弦向的体积干缩率随着树龄的增大而减小;相同树龄黑木相思的边材密度和力学性能比心材小,干缩率比心材大.因此,在利用黑木相思时应对树龄、心边材径向位置加以特别考虑.     

Factors influencing the formation of heartwood discolouration in sycamore (<Emphasis Type="Italic">Acer pseudoplatanus</Emphasis> L.)

Sycamore (Acer pseudoplatanus L.) is a tree species with highly valuable wood. Similar to European beech (Fagus sylvatica L.), the stemwood of sycamore can be devalued due to the discolouration i.e. brown heart (hearwood discolouration, hereafter). This paper aims to establish the influence of tree traits and site characteristics on the formation of heartwood discolouration and the possibility of predicting the occurrence of heartwood discolouration. For this purpose, 351 sycamore trees from 38 sites in Slovenia, most of them on carbonate bedrock and in the mountain vegetation belt, were analysed. Stem analysis was carried out on all the trees and the age, diameter at breast height (dbh), height of crown base, forking and crown size, were established. On the stump and upper fronts of the first and second logs, the maximum heartwood discolouration diameter was measured. Using logistic regression, the positive influence of age, relative crown length and average diameter increment on the formation of heartwood discolouration was ascertained. Conversely, the probability of heartwood discolouration was diminished by diameter increment in the last 20 years. In the less productive sites, the probability of formation of heartwood discolouration was relatively high in small diameter trees, but it increased slowly with diameter. Tree forking also contributed to a large extent of the heartwood discolouration. After the diameter at breast height achieves 45 cm, the formation of heartwood discolouration on the first log is highly probable. As in beech, the heartwood discolouration increases along the stem axis up to a height of 6–8 m, and decreases in the higher parts of the tree.     

Circumferential variation of heartwood and stem quality in maritime pine stems

Maritime pine (Pinus pinaster Ait.) is an important timber and pulpwood species covering about 4 million ha in Portugal, Spain and France. This work studied the cross-sectional distribution of heartwood and sapwood along the stem using 3D modelling on 20 trees. The target was to assess the potential of this species for the industrial production of heartwood sawn products. The maritime pine stems were characterized by wide sapwood of 10 cm, in average, and the presence of heartwood at all height levels with constant diameter up to 35 % tree height, decreasing afterwards. In the radial section, the heartwood follows a circumferential-like shape which changes along the stem. Pith eccentricity index values were low and homogeneous regarding to stem and higher for heartwood. Heartwood cross-sectional shape was constant up to 45 % of total height of the tree and more elongated upwards. The constant heartwood diameter, low taper and pith eccentricity index, and an approximate circular shape up to 10 m height indicated these species’ potential to produce solid wood products made out of heartwood.     

Collection of expressed genes from the transition zone of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> in the dormant season

Heartwood affects the utility of wood because it differs in some properties compared to sapwood. To regulate heartwood formation, its mechanism must be elucidated. However, the molecular basis underlying heartwood formation remains largely unknown. To obtain clues to understand the mechanism at a molecular level, we collected expressed sequence tags (ESTs) from the transition zone (TZ) of Cryptomeria japonica D. Don in November, in which heartwood formation is considered to proceed. A total of 1029 ESTs were assembled into 744 unique sequences (103 clusters and 641 singletons). Putative functions were assigned to 291 nuclear-encoded sequences, and they were grouped into 21 categories according to the eukaryotic orthologous groups functional classification. We selected 20 genes for enzymes or proteins, then examined their expression patterns among different organs. The expression levels of nine genes were higher in November than in June in the TZ. The genes encode two enzymes in glycolysis, invertase, methionine adenosyltransferase, glutathione transferase, the lipid transfer protein, Bet v 1 allergen, the dehydrin and the function-unknown protein. This study has provided the first large-scale EST information from the TZ of conifers, which will be useful for understanding the physiological processes in the TZ at a molecular level.     

Predicting the Stiffness of Sawn Products by X-ray Scanning of Norway Spruce Saw Logs

The aim of the study was to investigate the possibility of strength grading Norway spruce [Picea abies (L.) Karst.] saw logs on the basis of simulated X-ray LogScanner measurements and to evaluate the potential accuracy of X-ray LogScanner measurements of green heartwood density and percentage of heartwood. The study was based on 272 logs for strength grading and 29 logs for measurements of green heartwood density and percentage of heartwood. The logs were scanned using computed tomography (CT). After sawing, the modulus of elasticity (MOE) of the centre boards was measured using a strength-grading machine. The CT images were used for simulations of an X-ray LogScanner, resulting in simulated measurements of different variables such as diameter, taper, percentage of heartwood, density and density variations. Multivariate models for prediction of MOE were then calibrated using partial least squares (PLS) regression. The MOE of a log was defined as the mean value of the MOE of the two centre boards. The study showed that the simulated X-ray LogScanner measured the percentage of heartwood and green heartwood density with relatively high accuracy (R ² = 0.94 and R ² = 0.73, respectively, after removing two outliers) and that these and other variables measured by the simulated X-ray LogScanner could be used to predict the stiffness of the centre boards. These predictions were used to sort the logs according to the predicted MOE. When sorting out 50% of the logs (''high-strength'' logs), the percentage of C30 boards increased from 73% (all logs in the study) to 100% (only ''high-strength'' logs). The rest of the logs could then be divided into two groups, one of them with 100% C24 and C30 boards.     

Distribution,properties and formation of some wood extractives

Summary In the future, wood will be used largely for the manufacture of fibre products and particle board. The quality of wood used to meet increasing world demand will vary considerably. One feature of quality that can affect utilisation is the amount and type of wood extractives present. The distribution and variation in composition of extractives in the tree, as well as their effect on pulp manufacture, durability and surface films, are summarized. Methods to reduce the effects of some extractives in existing trees are described. Extractives can be reduced in plantation material by minimizing heartwood formation and by using silvicultural methods which result in small amounts of extractives being formed in this tissue. Current knowledge on heartwood formation is summarized.Paper presented to the 3rd Plenary Meeting of the International Academy of Wood Science held at the N. C. State University, Raleigh, March 11, 1971.     

Radial patterns of carbon isotopes in the xylem extractives and cellulose of Douglas-fir

Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (delta(13)C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer 39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their delta(13)C composition determined. Although the extractives and the cellulose showed different absolute delta(13)C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.