Quantitative Changes in Main Parameters of Secondary Xylem during Aging Process in Pinus bugeana

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Cellular level observation of water loss and the refilling of tracheids in the xylem of Cryptomeria japonica during heartwood formation

The mechanism of heartwood formation in Cryptomeria japonica D. Don has long been studied since heartwood formation is a fundamental physiological feature of trees. In this study, the water distribution in the xylem of C. japonica was investigated at the cellular level to reveal the role of water distribution in the xylem during heartwood formation. Samples were taken from different heights of each trunk, in which the phases of heartwood formation differed. These were designated as SIH, which consisted of sapwood, intermediate wood, and heartwood; SI, which consisted of sapwood and intermediate wood but no heartwood; and S-all, which consisted entirely of sapwood. Cryo-scanning electron microscopic observations of the heartwood-formed (SIH) and non-heartwood-formed (SI and S-all) xylem revealed different patterns of water distribution changes in tracheids between the latewood and earlywood. In the latewood, almost all tracheids were filled with water in all areas from the sapwood to the heartwood (98–100% of tracheids had water in their lumina). In the earlywood, however, the water distribution differed between the sapwood (95–99%), intermediate wood (7–12%), and heartwood (4–100%). Many of the tracheids in the xylem, where the sapwood changed to intermediate wood lost water. In the heartwood, some tracheids remained empty, while others were refilled with water. These results suggest that the water distribution changes in individual tracheids are closely related to heartwood formation. Water loss from tracheids may be an important factor inducing heartwood formation in the xylem of C. japonica.     

Xylem water content and wood density in spruce and oak trees detected by high-resolution computed tomography

Elucidation of the mechanisms involved in long-distance water transport in trees requires knowledge of the water distribution within the sapwood and heartwood of the stem as well as of the earlywood and latewood of an annual ring. X-ray computed tomography is a powerful tool for measuring density distributions and water contents in the xylem with high spatial resolution. Ten- to 20-year-old spruce (Picea abies L. KARST.) and oak (Quercus robur) trees grown in the field were used throughout the experiments. Stem and branch discs were collected from different tree heights, immediately deep frozen, and used for the tomographic determinations of spatial water distributions. Results are presented for single-tree individuals, demonstrating heartwood and sapwood distribution throughout their entire length as well as the water relations in single annual rings of both types of wood. Tree rings of the sapwood show steep water gradients from latewood to earlywood, whereas those of the heartwood reflect water deficiency in both species. Although only the latest two annual rings of the ringporous species are generally assumed to transport water, we found similar amounts of water and no tyloses in all rings of the oak sapwood, which indicates that at least water storage is important in the whole sapwood.     

Comparison of Dilute Acid and Sulfite Pretreatment for Enzymatic Saccharification of Earlywood and Latewood of Douglas fir

This study applied dilute acid (DA) and sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) to deconstruct earlywood and latewood cell walls of Douglas fir for fermentable sugars production through subsequent enzymatic hydrolysis. DA pretreatment removed almost all the hemicelluloses, while SPORL at initial pH?=?4.5 (SP-B) removed significant amount of lignin between 20 and 25 %. But both are not sufficient for effective enzymatic saccharification. SPORL at low initial pH?=?2 (SP-AB) combines the advantage of both DA and SPORL-B to achieve approximately 90 % hemicellulose removal and delignification of 10–20 %. As a result, SP-AB effectively removed recalcitrance and thereby significantly improved enzymatic saccharification compared with DA and SP-B. Results also showed that earlywood with significantly lower density produced less saccharification after DA pretreatment, suggesting that wood density does not contribute to recalcitrance. The thick cell wall of latewood did not limit chemical penetration in pretreatments. The high lignin content of earlywood limited the effectiveness of DA pretreatment for enzymatic saccharification, while hemicellulose limits the effectiveness of high pH pretreatment of SP-B. The higher hemicellulose content in the earlywood and latewood of heartwood reduced saccharification relative to the corresponding earlywood and latewood in the sapwood using DA and SP-AB.     

The accumulation pattern of ferruginol in the heartwood-forming Cryptomeria japonica xylem as determined by time-of-flight secondary ion mass spectrometry and quantity analysis

Background and Aims

Heartwood formation is a unique phenomenon of tree species. Although the accumulation of heartwood substances is a well-known feature of the process, the accumulation mechanism remains unclear. The aim of this study was to determine the accumulation process of ferruginol, a predominant heartwood substance of Cryptomeria japonica, in heartwood-forming xylem.

Methods

The radial accumulation pattern of ferruginol was examined from sapwood and through the intermediate wood to the heartwood by direct mapping using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The data were compared with quantitative results obtained from a novel method of gas chromatography analysis using laser microdissection sampling and with water distribution obtained from cryo-scanning electron microscopy.

Key Results

Ferruginol initially accumulated in the middle of the intermediate wood, in the earlywood near the annual ring boundary. It accumulated throughout the entire earlywood in the inner intermediate wood, and in both the earlywood and the latewood in the heartwood. The process of ferruginol accumulation continued for more than eight annual rings. Ferruginol concentration peaked at the border between the intermediate wood and heartwood, while the concentration was less in the latewood compared wiht the earlywood in each annual ring. Ferruginol tended to accumulate around the ray parenchyma cells. In addition, at the border between the intermediate wood and heartwood, the accumulation was higher in areas without water than in areas with water.

Conclusions

TOF-SIMS clearly revealed ferruginol distribution at the cellular level. Ferruginol accumulation begins in the middle of intermediate wood, initially in the earlywood near the annual ring boundary, then throughout the entire earlywood, and finally across to the whole annual ring in the heartwood. The heterogeneous timing of ferruginol accumulation could be related to the distribution of ray parenchyma cells and/or water in the heartwood-forming xylem.     

Effects of Infestation by the Balsam Woolly Aphid, Adelges Piceae (Ratz.) on the Ultrastructure of Bodered-Pit Membranes of Grand Fir, Abies grandis (Doug.) Lindl.

The ultrastructure of bordered-pit membranes in normal grandfir trees, Abies grandis (Doug.) Lindl., was compared with thatin trees infested with the blasam woolly aphid, Adelges piceae(Ratz). In sapwood of non-infested trees the membranes of earlywoodpits were well perforated, whereas those of latewood pits wereeither heavily incrusted or incompletely developed and showedfew perforations. In the heartwood pit membranes from both earlywoodand latewood were heavily incrusted. In aphid-infested trees all the pit membranes from the sapwoodwere incrusted and resembled those from heartwood of non-infestedtrees. These incurstations reduced the number of pores in themargo of pit membranes, and could account for the reduced permeabilityto water reported for sapwood trees attacked by the aphid. Wesuggest that the incrustation of pit membranes in sapwood inAbies grandis infested with Adelges piceae occurs because theseaphids cause heartwood to form prematurely.     

The function of intercellular spaces along the ray parenchyma in sapwood, intermediate wood, and heartwood of Cryptomeria japonica (Cupressaceae)

? Premise of the study: Intercellular spaces along ray parenchyma (ISRP) are common in many conifer xylems, but their function is uncertain because the in-situ structural network among ISRP, ray parenchyma, and tracheids has not been evaluated. Analysis of water distribution in ISRP from sapwood to heartwood is needed to elucidate the function of ISRP in sapwood, intermediate wood, and heartwood. ? Methods: We used cryo-scanning electron microscopy, x-ray photography, and water content measurement in xylem to analyze the presence of liquids in ISRP, ray parenchyma, and tracheids from sapwood to heartwood in Cryptomeria japonica (Cupressaceae). ? Key results: In sapwood, almost all ISRP were empty. "Cingulate-cavitated regions", which lose water along the tangential direction within one annual ring, formed in the earlywood tracheids, and their frequency increased toward the inner annual rings, whereas ray parenchyma cells were alive and not involved in the partial cavitation. In intermediate wood, almost all ISRP and earlywood tracheids and many of the ray cells were empty, and only some latewood tracheids retained liquid in their lumina. The ISRP were connected with tracheids via gas-filled ray parenchyma cells. ? Conclusions: The ISRP work as a pathway of gas for aspiration of ray parenchyma cells in sapwood. On the other hand, the occurrence of a gas network between ISRP, ray parenchyma, and tracheids facilitates cavitation of tracheids, resulting in the generation of low-moisture, intermediate wood.     

How do water transport and water storage differ in coniferous earlywood and latewood?

The goal of this research project was to determine the water transport behaviour of earlywood versus latewood in the trunk of 21-year-old Douglas-fir [Pseudostuga menziesii (Mirb.) Franco] trees. Specific conductivity (k(s)) and the vulnerability of xylem to embolism were measured on a single growth ring and in a subset of earlywood and latewood samples within the same ring. Earlywood/latewood ratio, trunk water potential (Psi) and relative water content (RWC) were used to predict differences in conductivities and vulnerability to embolism. Earlywood has about 11 times the k(s) of latewood, and up to 90% of the total flow occurred through the earlywood. Earlywood's vulnerability to embolism followed the same trend as that of the whole wood, with 50% loss of conductivity at -2.2 MPa (P(50)). Latewood was more vulnerable to embolism than earlywood at high Psi, but as Psi decreased, the latewood showed very little further embolism, with a P(50) <-5.0 MPa. The lowest trunk Psi estimated in the field was about -1.4 MPa, indicating that latewood and earlywood in the field experienced about 42% and 16% loss of k(s), respectively. The higher vulnerability to embolism in latewood than in earlywood at field Psi was associated with higher water storage capacity (21.8% RWC MPa(-1) versus 4.1% RWC MPa(-1), latewood and earlywood, respectively). The shape of the vulnerability curve suggests that air seeding through latewood may occur directly through pores in the margo and seal off at lower pressure than earlywood pores.     

The effects of cambial age and position within the stem on specific conductivity in Douglas-fir (Pseudotsuga menziesii) sapwood

Specific conductivity (k_s, m²s^-1MPa^-1) describes the permeability of xylem and is determined by all aspects of xylem anatomy that create resistance to the flow of water. Here we test the hypothesis that k_s is a function of radial and vertical position within the stem, rather than solely a function of cambial age (ring number from the pith), by measuring k_s on samples excised from 35-year-old Douglas-fir [Pseudotsuga menziesii var. menziesii (Mirb.) Franco] trees at six heights and two or three radial positions. Sapwood k_s decreased from the cambium to the heartwood boundary, and the difference between outer and inner sapwood increased with height in the tree. Beneath the live crown, inner sapwood had 80-90% the k_s of outer sapwood, but only 55% just 10 m higher in the stem (about 10 nodes down from the tree top). Outer sapwood k_s peaked near the base of the crown and declined toward both the base and top of the stem. These patterns can be explained by two superimposed effects: the effect of cambial age on the dimensions of tracheids as they are produced, and the effect of xylem aging, which may include accumulation of emboli and aspiration of bordered pits. Tracheid lumen diameter and earlywood and latewood density and width, all factors known to vary with cambial age, were measured on different trees of the same age and from the same stand. Lumen diameter increased with cambial age, whereas the proportion of latewood and growth ring density increased after an initial decrease in the first 5 years. Our results suggest that the effect of cambial age on xylem anatomy is not sufficient to explain variation in k_s. Instead, physical position (both vertical and radial) in the stem and cambial age must be considered as determinants of conductivity.     

Force–displacement measurements of earlywood bordered pits using a mesomechanical tester

The elastic properties of pit membranes are reported to have important implications in understanding air‐seeding phenomena in gymnosperms, and pit aspiration plays a large role in wood technological applications such as wood drying and preservative treatment. Here we present force–displacement measurements for pit membranes of circular bordered pits, collected on a mesomechanical testing system. The system consists of a quartz microprobe attached to a microforce sensor that is positioned and advanced with a micromanipulator mounted on an inverted microscope. Membrane displacement is measured from digital image analysis. Unaspirated pits from earlywood of never‐dried wood of Larix and Pinus and aspirated pits from earlywood of dried wood of Larix were tested to generate force–displacement curves up to the point of membrane failure. Two failure modes were observed: rupture or tearing of the pit membrane by the microprobe tip, and the stretching of the pit membrane until the torus was forced out of the pit chamber through the pit aperture without rupture, a condition we refer to as torus prolapse.     

Seasonal and perennial changes in the distribution of water in the sapwood of conifers in a sub-frigid zone

An analysis was made of progressive changes in patterns of cavitation in the sapwood of three species of conifer (Larix kaempferi, Abies sachalinensis, and Picea jezoensis) that were growing in a sub-frigid zone. In all three conifers, all tracheids of the newly forming outermost annual ring were filled with water or cytoplasm during the period from May to August. However, many tracheids in the transition zone from earlywood to latewood lost water in September, presumably through drought-induced cavitation. Cavitated tracheids tended to be continuously distributed in a tangential direction. Subsequently, some earlywood tracheids of the outermost annual ring lost water during the period from January to March. This was associated with freeze-thaw cycles. In the second and third annual rings from the cambium of all three conifers, the lumina of most tracheids in the transition zone from earlywood to latewood contained no water. In contrast, some latewood tracheids near the annual ring boundary and many earlywood tracheids retained water in their lumina. The third annual ring had more cavitated tracheids than the second annual ring. Our observations indicated that cavitation progressed gradually in the tracheids of the conifers and that they were never refilled once cavitation had occurred. The region involved in water transport in conifers did not include the entire sapwood and differed among annual rings.     

Water Permeability of the Wood of Grand Fir (Abies grandis (Doug.) Lindl.) in Relation to Infestation by the Balsam Woolly Aphid, Adelges piceae (Ratz.)

The water permeability of sapwood and heartwood of Abies grandis(Doug.) Lindl. was found for normal trees and those infestedby balsam woolly aphid Adelges Piceae (Ratz.). It was determinedas the rate of flow of water through plugs of the wood of standarddimensions and under constant suction. The permeability of normaltrees was less in the inner than the outer sapwood and thisdifference was correlated with a greater void space (gas-filledtracheids) in the inner sapwood. The permeability of the heartwoodwas less than 5 per cent that of the sapwood. Aphid infestationreduced the permeability of the outer sapwood to about the samelevel as normal heartwood. The infested wood had a high percentageof void space and again permeability was negatively correlatedwith void space. But for a given level of void space the infestedwood had a much lower permeability than normal wood. This suggeststhat there was factor additional to the air in the tracheids,which contributed to the low permeability of infested wood.The possible nature of this factor is briefly discussed.     

Tetracentron Wood from the Miocene of Noto Peninsula,Central Japan,with a short revision of homoxylic fossil woods

A vesselless fossil wood was discovered in the Miocene Yanagida Formation in the Noto Peninsula, central Japan. This fossil has distinct growth rings with gradual transition from the early- to the latewood ; tracheids, which are called 'usual traeheids' here, constitute the ground mass of the wood and have typical scalariform bordered pits on radial walls in the earlywood and circular sparse pits on those in the latewood ; rays are 1\2-4 cells wide and heterogeneous with low to high uniseriate wings; axial parenchyma strands are scattered in the latewood. This wood has a peculiar feature; sporadic radial files of broad tracheids whose tangential walls have crowded alternate bordered pits. The radial walls have crowded half-bordered pits to ray cells, but no pits to the usual tracheids. Among all of the extant and extinct angiosperms and gymnosperms, these unusual tracheids occur only in Tetracentron. From these features, we refer the fossil to the extant genus Tetracentron, and name it T. japonoxylum. A revision of homoxylic woods is made for comparision with the present fossil. Tetracentron japonoxylum is the only fossil wood of Tetracentron.     

不同林分类型林缘华北落叶松细胞特征

以塞罕坝机械林场华北落叶松纯林及华北落叶松-白桦混交林为对象,研究林地边缘华北落叶松边界木与林内木径向生长、年轮细胞大小及数量的差异,分析林缘对不同林分类型华北落叶松径向生长及细胞特征的影响。结果表明: 纯林中边界木的径向生长显著快于林内木,年轮总宽、早材和晚材总生长量在边界木较林内木分别增加48.9%、58.9%和29.6%,而混交林边界木与林内木的径向生长差距并不明显。纯林边界木早材细胞总数、早材大细胞和小细胞数量较林内木分别增加63.3%、55.6%和70.0%,晚材细胞总数、晚材大细胞和小细胞数量边界木较林内木分别增加35.4%、37.5%和28.5%,而早晚材细胞大小在边界木与林内木间无显著差异。混交林边界木早晚材细胞数量与林内木无显著差异,但边界木早材细胞大小较林内木增大50.0%,边界木早材最大细胞、最小细胞、大细胞及小细胞的大小较林内木分别增大28.6%、33.3%、16.6%和25.0%。通过混交的方式营造混交林可以有效地缓解林缘导致的纯林中边界木生长过快而林内木生长较慢的现象。     

Formation of heartwood substances in the stemwood of Robinia pseudoacacia L. II. Distribution of nonstructural carbohydrates and wood extractives across the trunk

Summary The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (>1 mol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.Dedicated to Prof. Meinhart H. Zenk on the occasion of his 60th birthday     

Anatomy of the vessel network within and between tree rings of Fraxinus lanuginosa (Oleaceae)

The three-dimensional (3-D) arrangement of vessels and the vessel-to-vessel connections in the secondary xylem of the stem of the ring-porous hardwood tree Fraxinus lanuginosa were studied in series of thick transverse sections with epifluorescence microscope and confocal laser scanning microscope. Vessels were traced in sequential sections, and vessel networks were reconstructed in two segments of wood with dimensions of 2 × 1.4 × 21.2 mm(3) and 2 × 1.4 × 5.8 mm(3) (tangential × radial × axial). The arrangement of vessels and intervessel pits were visualized by scanning electron microscopy in low-density polyethylene microcasts and on exposed tangential faces of growth-ring boundaries. The vessels deviated from the stem axis in the tangential direction and, to a lesser extent, in the radial direction. Some neighboring vessels were twisted around each other. Vessels that appeared solitary in single sections were found to be sequentially contiguous with a number of other vessels, forming networks that extended in the tangential direction and across growth-ring boundaries. In the 21.2-mm wood block, all earlywood vessels at the growth-ring boundary made contact with latewood vessels in the previous tree ring. Within a growth ring however, only a single contact was observed between individual earlywood and latewood vessels. Densely arranged intervessel pits were characteristic in the regions where adjacent vessels made contact with each other. Such bordered pits were abundant in the tangential walls of vessel elements adjacent to growth-ring boundaries. Therefore, bordered pits appear to provide the pathway for the radial transport of water via the vessel network across growth-ring borders. Fiber-tracheids, observed as terminal cells in the tree rings, might also contribute to the apoplastic transfer of water across ring borders.     

Mechanical Properties of Black Locust (Robinia pseudoacacia) Wood: Correlations among Elastic and Rupture Moduli,Proportional Limit,and Tissue Density and Specific Gravity

The purpose of this paper is to determine the extent to which the physical and mechanical properties of dry and green wood samples are correlated. Samples of green (fresh) sap- and heartwood differing in density (ρ) were removed from the trunk of a black locust (Robinia pseudoacaciaL.) tree 30 years old and measuring 15 m in height. These samples were mechanically tested to determine their Young's elastic modulus (E), proportional (elastic) limit (σ_p), and modulus of rupture (σ_R). The Young's elastic modulus of green wood samples increased in magnitude to a limit with increasing cross-sectional area of the sample tested. The values of all three mechanical parameters measured for sapwood samples were consistently lower than those measured for heartwood samples with equivalent cross-sectional areas.Ewas linearly and positively correlated with the σ_pand σ_Rof heartwood tissue samples. All mechanical properties were highly correlated with the density of green heartwood. Likewise, these properties were highly correlated with the specific gravity of wood samples. Based on these results, it is concluded that either the density of fresh wood or the specific gravity of air-dried wood can be used to estimate the mechanical properties of black locust wood based on simple regression curves in the absence of extensive mechanical tests.     

Soluble carbohydrates of Pinus sylvestris L. sapwood and heartwood

Summary The amounts of glucose, fructose, sucrose, arabinose/galactose, raffinose/stachyose and starch were investigated in the outer sapwood, innermost sapwood, transition zone and heartwood of four stems of Pinus sylvestris L. The samples were taken in October and the determination of the compounds was done enzymatically. It was not possible to distinguish arabinose from galactose and raffinose from stachyose. The amounts of glucose, fructose and sucrose were greatest in the outer sapwood and decreased gradually towards the innermost sapwood and the heartwood. In the outermost heartwood glucose, fructose and sucrose were only present in trace amounts. Raffinose/stachyose showed highest concentrations in the outer sapwood and decreased towards the heartwood. In contrast, the concentrations of arabinose/galactose increased towards the heartwood and the greatest amount was found in the inner heartwood. When identified by thin-layer chromatography (TLC), arabinose was found to be present in greater amounts than galactose. The amount of starch decreased markedly towards heartwood. However, the amounts of sugars in all the studied stems was very variable. The changes in the amounts of carbohydrates in the different zones of the stems and the possible relationships of these phenomena with heartwood formation are discussed.     

Heartwood and sapwood development within maritime pine (<Emphasis Type="Italic">Pinus pinaster </Emphasis>Ait.) stems

Heartwood and sapwood development in maritime pine (Pinus pinaster Ait.) is reported based on 35 trees randomly sampled in four sites in Portugal. It was possible to model the number of heartwood rings with cambial age. The heartwood initiation age was estimated to be 13 years and the rate of sapwood transformation into heartwood was 0.5 and 0.7 rings year^–1 for ages below and above 55 years, respectively. Reconstruction of heartwood volume inside the tree stem was made by visual identification by image analysis in longitudinal boards along the sawn surfaces. This volume was integrated into the 3D models of logs and stems developed for this species representing the external shape and internal knots. Heartwood either follows the stem profile or shows a maximum value at 3.8 m in height, on average, while sapwood width is greater at the stem base and after 3 m remains almost constant up the stem. Up to 50% of tree height heartwood represents 17% of stem volume, in 83-year-old trees and 12–13% in 42 to 55-year-old trees. Tree variables such as stem diameter, DBH and tree total height were found to correlate significantly with the heartwood content.     

Linkages between forest growth,climate, and agricultural production are revealed through analysis of seasonally-partitioned longleaf pine (Pinus palustris Mill.) tree rings

We established a five-century long tree-ring chronology partitioned between earlywood and latewood growth to examine intra-annual climate response and attempt to establish linkages to agricultural production. Longleaf pine earlywood and latewood width chronologies spanned the period 1491–2017 (527 years) and constitute one of the longest records achieved for this species. High monthly correlations were found between latewood growth and summer-fall Palmer Drought Z-Index. Correlations were consistently significantly positive for June through October. Intra-annual growth of earlywood and latewood were positively correlated for the full period of record, but exhibited variability in correlation strength through time. Conversely, earlywood and prior-year latewood were also frequently correlated, but correlations were found to switch between positive and negative association, possibly in response to Atlantic Ocean temperatures. Annual yields of major crops are coupled with latewood growth, representing a new and potentially valuable proxy for linking agricultural yields to climate proxies over multiple centuries.