Peroxidase activity, isoenzymes and histological localisation in sapwood and heartwood of Scots pine (Pinus sylvestris L.)

Peroxidase activity and isoenzymes of fresh wood samples of the third shoot of 12-year old trees and from the sapwood, transition zone and heartwood of c. 60-year old stems of Scots pine (Pinus sylvestris L.) were investigated. Wood samples were ground at −30°C, extracted, and the extracts concentrated c. 20-fold for peroxidase activity assays (guaiacol method) and for IEF-PAGE. At least 11 major isoenzymes could be found in the gels. Even the heartwood contained some peroxidase isoenzymes. Isoenzyme patterns of the juvenile wood did not change with the season. However, juvenile wood showed the highest peroxidase activity at the end of the growing season. Peroxidase activity decreased from the outer sapwood towards the heartwood. Thin sections of different wood zones stained for peroxidase revealed activity in ray parenchyma and resin canal epithelial cells. Intensive staining was localised in the bordered pits of vertical and ray tracheids, and in the end walls of ray parenchyma cells.     

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.     

Chemical composition of earlywood and latewood in Norway spruce heartwood,sapwood and transition zone wood

This study focused on the distribution of wood components along a cross section of a spruce stem. Thin samples of earlywood and latewood were analysed by special micro-scale analytical techniques. Heartwood contained significantly more lignin and less cellulose than sapwood. The total content of hemicelluloses was the same along the radial direction, but the distribution of sugar units differed. The amounts of arabinoglucuronoxylan and pectins were larger in the heartwood. The transition zone between heartwood and sapwood had a specific composition, with less lignin and lipophilic extractives than heartwood and sapwood. For earlywood and latewood, significant differences were found in the distribution of sugar units in hemicelluloses. Latewood contained clearly more galactoglucomannan than earlywood, and conversely less pectins. The lipophilic extractives were also less concentrated in the latewood.Abbreviations EW or E earlywood - LW or L latewood - HW heartwood - SW sapwood - TZ transition zone wood - A.R. annual ring - AcBr Acetyl bromide - Ara arabinose - Xyl xylose - Gal galactose - Glc glucose - Man mannose - Rha rhamnose - GlcA glucuronic acid - MGlcA 4-O-methyl-glucuronic acid - GalA galacturonic acid - o.d. oven dry     

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.     

Wood properties of juvenile and mature heartwood in Robinia pseudoacacia L.

The aim of this study is to characterise the properties of juvenile and mature heartwood of black locust (Robinia pseudoacacia L.). Content, composition and the subcellular distribution of heartwood extractives were studied in 14 old-growth trees from forest sites in Germany and Hungary as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to topochemically localise the extractives in the cell walls. The natural durability of the juvenile and mature heartwood was analysed according to the European standard EN 350-1. Growth as well as chemical analyses showed that, based on extractives content, the formation of juvenile wood in black locust is restricted to the first 10–20 years of cambial growth. In mature heartwood, high contents of phenolic compounds and flavonoids were present, localised in high concentrations in the cell walls and cell lumen of axial parenchyma and vessels. In juvenile wood, the content of these extractives is significantly lower. Juvenile wood had a correspondingly lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) than mature heartwood.     

The influence of heartwood on the pulping properties of Acacia melanoxylon wood

The pulping wood quality of Acacia melanoxylon was evaluated in relation to the presence of heartwood. The sapwood and heartwood from 20 trees from four sites in Portugal were evaluated separately at 5% stem height level in terms of chemical composition and kraft pulping aptitude. Heartwood had more extractives than sapwood ranging from 7.4% to 9.5% and from 4.0% to 4.2%, respectively, and with a heartwood-to-sapwood ratio for extractives ranging from 1.9 to 2.3. The major component of heartwood extractives was made up of ethanol-soluble compounds (70% of total extractives). Lignin content was similar in sapwood and heartwood (21.5% and 20.7%, respectively) as well as the sugar composition. Site did not influence the chemical composition. Pulping heartwood differed from sapwood in chemical and optical terms: lower values of pulp yield (53% vs 56% respectively), higher kappa number (11 vs. 7), and lower brightness (28% vs 49%). Acacia melanoxylon wood showed an overall good pulping aptitude, but the presence of heartwood should be taken into account because it decreases the raw-material quality for pulping. Heartwood content should therefore be considered as a quality variable when using A. melanoxylon wood in pulp industries     

Impregnation of radiata pine wood by vacuum treatment II: effect of pre-steaming on wood structure and resin content

Radiata pine sapwood and heartwood were dried using high-temperature, conventional-temperature, and air drying schedules with and without pre-steaming. They were then impregnated by vacuum treatment with double-distilled water, toluidine blue, and fluorescein dye. For sapwood, there were only minor differences in uptake between drying methods and when pre-steaming was used. Using microscopy, the primary flow pathways in sapwood were found to be the resin canal network and ray parenchyma cells, which provided conduction without large resistance. In heartwood, uptake was strongly influenced by pre-steaming the green lumber. After pre-steaming heart-wood, there was an increase in uptake from all surfaces but especially from the radial surfaces. Lower extractive contents, disruption of epithelial and ray parenchyma cells, and alteration of the condition of bordered pits were also associated with pre-steaming. It was therefore possible to classify flow paths in radiata pine heartwood five ways, according to uptake values and wood anatomical features.This research was presented in part at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998.     

Heartwood,its function and formation

Summary Some of the changes which occur in wood during the transition from sapwood to heartwood have been reviewed. The nature of these changes suggest that heartwood formation is a regulatory process serving to keep the amount of sapwood at an optimum level. The pattern formed by the transition of cells from sapwood to heartwood suggests that heartwood development is controlled by a centripetally-translocated growth-active substance. The nature of the heartwood transformation is indicative of a developmental process rather than a deterioration of cell function with age so that death of the parenchyma cells is the result and not the cause of heartwood formation.The assistance of Jeanette Gregory, transmission electron microscopy; Dianne Higginbotham, scanning electron microscopy; N. Omar, statistical analysis; C. Taylor, photography; F. R. Humphreys, D. Edwards, D. Adamson, R. C. Foster, and F. V. Mercer, critical comments, is acknowledged. The scanning electron microscopy was undertaken at the Electron Microscopy Unit, Sydney University with the kind co-operation of C. Nockolds. The permission of Marcia Lambert to use unpublished data in Table 2 is also acknowledged.     

Changes in the morphology and functions of vacuoles during the death of ray parenchyma cells in <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>

Changes in the morphology and functions of vacuoles provide useful information about the mechanism of cell death. In the present study, we monitored the morphology and contents of vacuoles during the death of ray parenchyma cells in the conifer Cryptomeria japonica. In differentiating xylem, ray parenchyma cells had large central vacuoles. In sapwood, vacuoles in ray parenchyma cells contained proteins, an indication that one of the main functions of these vacuoles might be protein storage. A dramatic decrease in the protein content of some vacuoles was detected in the intermediate wood before the initiation of vacuole rupture. Although vacuole rupture was detected from the intermediate wood to the outermost heartwood, some vacuoles were obviously enlarged in the inner intermediate wood. Condensed nuclei were first observed after the rupture of these large vacuoles in ray parenchyma cells. It seems plausible that the autolysis of the contents of ray parenchyma cells might be caused by the rupture of the enlarged vacuoles in the inner intermediate wood.     

Heartwood and sapwood variation in Eucalyptus globulus Labill. trees at the end of rotation for pulp wood production

The amount of heartwood and sapwood in Eucalyptus globulus Labill. wood was determined in commercial pulpwood plantations at harvest age (12 to 15 years) in four ites in central portugal. twelve trees were sampled in each site at nine stem height levels. Heartwood was present in all the trees up to 82%–87% of the total tree height and amounted to 38%–41% of the total tree volume. The heartwood proportion in the stem cross-section decreased from the base upwards, representing 53.3% and 26.1% of the total area respectively at the base and 55% height level. The sapwood width remained relatively constant along the stem at a mean 38 mm up to the 55% height level. The trees within the site, the height level and their interaction were highly significant sources of variation for heartwood proportion and sapwood width. The heartwood diameter and sapwood width were positively correlated with radial tree growth.     

Radial movement of sapwood-injected rubidium into heartwood of Japanese cedar (<Emphasis Type="Italic">Cryptomeria</Emphasis><Emphasis Type="Italic">japonica</Emphasis>) in the growing period

Rubidium solution was injected in the sapwood of a Japanese cedar cultivar in the growing period, and its radial movement in stem was traced to investigate the accumulation of alkali metals in the heartwood. Sapwood-injected Rb was detected in outer heartwood at 10 days after the treatment, and continued increasing at 20 days after. Radial movement of Rb toward heartwood was considered to occur soon after the treatment, and to decline at a certain point of the time after Rb injection ceased. However, Rb continued moving in heartwood probably by diffusion even after the cease of Rb injection. In a series of injection experiment, radial movement of injected Rb is not corresponding to the seasonality of both cambial activity and cytological changes of ray parenchyma accompanied with heartwood formation. From the results on Rb’s behavior, we conclude that accumulation of K and other alkali metals in heartwood of Japanese cedar has two steps, active transport from sapwood to outer heartwood via ray, and diffusion in heartwood, and that these processes proceed independently from both cambial activity and cytological changes of ray parenchyma.     

End grain water absorption and redistribution in slow-grown and fast-grown Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood

Abstract

Wood is susceptible to decay by rot fungi if it is exposed to high-moisture contents during long periods of time and it is therefore important to limit the duration of such periods. Critical points in outdoor wood structures are, for example, end grain surfaces in joints where water can get trapped after a rain. It is therefore of interest to study both absorption and redistribution of moisture in wood. This paper presents moisture content profiles during end grain water absorption and redistribution in Norway spruce (Picea abies (L.) Karst.) measured by computed tomography with the specimens in individual climate boxes. Heartwood and sapwood of two provenances (slow-grown and fast-grown wood) were included. No major differences were seen between the water uptake of the slow-grown and the fast-grown wood since the densities were similar despite of the large difference in growth ring width. However, for the sapwood specimens, the moisture content was higher further into the specimens than for the heartwood specimens in agreement with previous studies. For the slow-grown wood, the redistribution was also generally more rapid for the sapwood specimens than for the heartwood specimens.     

西加云杉木材中单宁的提取、分布及组分

研究西加云杉木材中植物单宁的提取工艺、分布和组分构成,为木材单宁变色的防治提供参考。采用有机溶剂萃取法,通过单因素试验并结合L9(34)正交试验,优化西加云杉木材中植物单宁的提取工艺;采用香草醛-紫外法测定西加云杉木材内植物单宁在径向(由髓心至树皮方向)和轴向的含量分布;通过定性鉴定试验确定单宁类型,并采用高效液相色谱法测定西加云杉木材中单宁的成分构成及其相对含量。结果表明:西加云杉木材中单宁最佳提取条件为70%(体积分数)乙醇作为提取溶剂,提取温度70℃,提取时间2 h,料液比1∶18(g∶m L),提取次数2次;单宁含量在径向上分布情况为内部心材单宁含量5.440 mg/g,近心边材转换区的心材部分单宁含量最高,平均达10.015 mg/g,心边材转换区部位单宁含量介于心材和边材之间,平均为6.363 mg/g,靠近转换区的边材部位单宁含量最低,平均为4.821 mg/g,近树皮边材含量为6.997 mg/g。西加云杉木材内5种原花青素成分含量存在明显差异,其中儿茶素含量最高,占5种原花青素总量的83.21%,原花青素B2次之。由此可知,有机溶剂法适用于西加云杉木材中单宁的提取;木材中单宁含量径向分布自髓心至树皮整体呈现出先增后减再增、心材大于边材的规律,轴向分布规律表现为下部含量略高于上部,但差异不显著;西加云杉木材内植物单宁类型为缩合单宁,儿茶素为西加云杉木材单宁的主要成分。     

广西融水特色红心杉木优树材质性状变异规律研究

[目的]通过测定和分析广西融水种源红心杉木优树材质性状指标,以了解该地区红心杉木材性状变异规律。[方法]以广西融水种源60株20年生的红心杉木优树为研究材料,测定单株材积、红心率、基本密度、组织比量、管胞性状、微纤丝角等10个材质性状指标,分析各材性性状指标分布和变异规律及性状间的相关关系。[结果]表明:红心率、基本密度、木射线比量、管胞比量、管胞长、管胞宽、管胞长宽比等性状数据分布服从正态分布。融水两个地区红心杉优树轴向薄壁细胞比量的变异系数分别为35.08%和44.97%,变异较大。管胞比量变异系数分别为3.28%和3.56%,变异较小。红心率、木射线比量、管胞长、管胞宽、微纤丝角等性状差异极显著(P0.01),轴向薄壁细胞比量差异显著(P0.05)。10个材质性状间存在12对表型显著相关。[结论]测定的10个性状均是连续性数量性状。早、晚材的管胞长度、管胞宽度和管胞长宽比等性状数据呈从心材至边材逐渐增加的规律。作为重要经济性状的红心率与木射线比量呈极显著正相关(P0.01),单株材积与轴向薄壁细胞比量呈显著正相关(P0.05),而单株材积与基本密度的相关性不显著,这使红心杉木生长量与材性相结合的遗传改良成为可能。     

Heartwood/sapwood variation of western redcedar as influenced by cultural treatments and position in tree

We studied heartwood and sapwood variation in western redcedar (Thuja plicata) at three sites, including a 95-year-old naturally regenerated, unmanaged stand, a 35-year-old planted spacing trial, and a 30-year-old naturally regenerated stand to which thinning and fertilization treatments had been applied. In the 95-year-old stand, we studied within-tree variation in heartwood and sapwood. In the thinning/fertilization trial and the planted spacing trial, we studied effects of cultural practices and growth rate on heartwood and sapwood. In the trees that we studied, sapwood width was generally fairly narrow, rarely exceeding 3.5 cm. Heartwood formation in western redcedar appeared to begin at a relatively small stem diameter (7 cm) and at a young age, probably 10–15 years. The amount and proportion of heartwood increased with distance downward from the top of the tree, with the implication that older trees will contain a greater proportion of heartwood than younger trees. For any given age, it appears that cultural treatments that favor rapid growth will result in stems with greater amounts of both sapwood and heartwood, and a greater proportion of heartwood.     

Soft X-ray observation of water distribution in the stem ofCryptomeria japonica D. Don I: General description of water distribution

Water distribution in green stems ofCryptomeria japonica D. Don was observed by soft X-ray photography. In the sapwood, much water was present and evenly distributed. In the intermediate wood (the white zone), little water was present. The intermediate wood appeared in all cross sections of the stem and separated the heartwood from the sapwood in the intertracheid water connection. Maldistribution of water was generally observed in the heartwood, and three types of water presence were distinguishable: a “wet area” with accumulated water, a “dry area” with little water, and a “moderate moisture area” with intermediate accumulation. The distribution pattern and amount of water in the heartwood varied dramatically among and even within trees. Separation of the heartwood from the sapwood in the intertracheid water connection suggested that the presence of water in the heartwood was caused by rewetting of the tracheid lamina that occurred after heartwood formation. The maldistribution of water in the heartwood suggested that a difference in the process of rewetting causes both uneven distribution and the various types of water presence.     

Heartwood, sapwood and bark content of teak trees grown in Karnataka, India

We evaluated heartwood, sapwood and bark content in teak trees. A total of 27 sample plots were laid out in teak plantations raised by State Forest Department in Karnataka covering different age groups...     

Temporally and spatially controlled death of parenchyma cells is involved in heartwood formation in pith regions of branches of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> var. <Emphasis Type="Italic">inermis</Emphasis>

Focussing on four types of parenchyma cell around pith regions of branches of Robinia pseudoacacia L. var. inermis, we examined the timing and role of cell death during heartwood formation. Large parenchyma cells that were located in the inner part of the pith died within a year. By contrast, other parenchyma cells died within 4 years, with the timing of cell death depending on the type of cell. Axial parenchyma cells of the xylem close to the pith died first. Then, small parenchyma cells died in the perimedullary zone in the outer part of the pith. Finally, ray parenchyma cells in the xylem close to the pith died. Variations in the autofluorescence of cell walls, which might have been due to deposition of heartwood substances, were observed first in xylem ray parenchyma cells and small parenchyma cells in the perimedullary zone. Our results indicate that the initiation of heartwood formation occurs within 4 years in pith regions of branches in Robinia pseudoacacia L. var. inermis. Moreover, it appears that not only xylem ray parenchyma cells but also small parenchyma cells in the perimedullary zone might be involved in the synthesis of heartwood substances.     

Polysaccharides in some industrially important softwood species

The content and composition of carbohydrates comprising polysaccharides in sapwood and heartwood of 12 industrially important pulpwood species were analysed. The polysaccharide content was between 60% and 80% (w/w) for all species, with cellulose as the predominant polysaccharide type. The carbohydrate composition suggested that the main non-cellulose polysaccharides were galactoglucomannans, except in Larix heartwood, where arabinogalactans were predominant, while the content of xylans were in the same range as the mannans in Pinus resinosa heartwood and Thuja occidentalis heartwood and sapwood. Pectins, i.e. polygalacturonic acids, were the main acidic polysaccharides in all species. The amount and composition of water-soluble carbohydrates from ground wood samples were also analysed, since these are important in mechanical pulping and as a possible source of bioactive polymers. The main polysaccharides released from the spruce species were mannans, together with starch from sapwood. Especially Abies balsamea stemwood, but also Abies sibirica heartwood, released considerable amounts of pectins, suggesting that fir species may release more troublesome anionic polysaccharides than spruce species. Heartwood of Larix lariciana, Larix decidua, Pinus banksiana, and Pinus resinosa released considerable amounts of acidic arabinogalactans. Thuja occidentalis released mainly arabinogalactans and pectins. Pseudotsuga menziesii heartwood released a large amount of arabinogalactans.