Determination of the distribution and reaction of polysaccharides in wood cell walls by the isotope tracer technique VII: Double radiolabeling of xylan and pectin in magnolia (Magnolia kobus DC) and comparison of their behaviors during kraft pulping by radiotracer technique

myo-Inositol-[2-³H] and d-glucuronic acid-[6-¹⁴C] were administered simultaneously to a growing stem of magnolia (Magnolia kobus DC) to label xylan and pectin, respectively, in the cell wall. Determination of the radioactivity of nitrobenzene oxidation products and sulfuric acid hydrolysates of the newly formed xylem indicated that xylan and pectin were labeled with ³H and ¹⁴C, respectively. The doubly labeled wood tissue was treated to kraft pulping, and the radioactivity of the pulping black liquor and treated wood tissue were determined at various stages of the pulping to compare the dissolving behavior between pectin and xylan during the pulping. The results showed that pectin was not dissolved as easily as xylan and was not redeposited on pulp fiber at the late stage of the pulping.Part of this report was presented at the 40th Lignin Symposium at Tsukuba, October 1995     

A study on some anatomical parameters of the piercing-sucking process in leaves and branches of<Emphasis Type="Italic"> Pittosporum tobira</Emphasis> L. (Pittosporaceae) infested by the cottony cushion scale,<Emphasis Type="Italic"> Icerya purchasi</Emphasis> Maskell (Homoptera: Coccina,Margarodidae)

Pittosporum tobira L. (Family Pittosporaceae) is an important plant species grown in parks and gardens in Turkey. The cottony cushion scale, Icerya purchasi Maskell (Homoptera: Coccina, Margarodidae), is an important pest of P. tobira, and causes damage mainly to the leaves, branches and stems of the host plant. In spite of the great economic importance of I. purchasi to its host plant P. tobira, information has been limited on some basic anatomical parameters of the nature of the damage to leaves and branches. The present study was, therefore, initiated to investigate the insertion and penetration of stylets into the leaves and branches of P. tobira, the length of stylets and depth of penetration in both of these tissues, and penetration of stylets into the cortex, xylem and phloem tissues and into the secretory and non-secretory canals of the leaves and branches. The results showed great variations between the leaves and branches in all the criteria observed in I. purchasi infesting P. tobira. The study found 20 whole and 23 broken mouthparts in the leaves as compared to 3 whole mouthparts and 1 broken in the branches. Length of the stylets inserted into the leaves ranged from 33.83 m to 540.93 m and into the branches from 202.85 m to 340.8 m. The stylets reached greater depths in the leaves, at 540.93 m, as compared to 498.67 m in the branches. The stylets in the leaves were associated with 12 secretory canals, but with none in the branches. It was found that three stylets reached xylem in the leaves as compared to one in the branches. Similarly, 17 stylets in the leaves reached to the phloem, but only 2 in the branches. No stylets were found in the cortex of the leaves, but one was found in the branches. In the leaves, 11 stylets reached and remained in the non-secretory canals, but none in the case of the branches.     

The effect of day length on diurnal differences in the innermost surface of the S2 layer in differentiating tracheids

This article describes the effect of day length during the photoperiodic cycle on the diurnal differences in the innermost surface of developing secondary walls. Saplings of Cryptomeria japonica D. Don. were grown in growth chambers at constant temperature and relative humidity, but with different photoperiods. Samples of differentiating xylem were collected during the light and dark periods. The innermost surface of developing secondary walls in differentiating tracheids were observed using field emission scanning electron microscopy, and observations made during the light and dark periods were compared. In the saplings grown under long-day or short-day conditions, diurnal differences in aspects of the innermost surface of developing secondary walls were observed. Cellulose microfibrils were observed on the innermost surface of developing secondary walls during the light period when the volumes of differentiating cells were low, and amorphous material was observed during the dark period, when differentiating tracheids were turgid. The amorphous material was labeled with antiglucomannan antiserum. These results suggest that the range of day-length conditions set in this study does not affect the diurnal periodicity in the supply of cell wall components to the innermost surface of developing secondary walls.     

Molecular cloning of a cellulose synthase gene PtoCesA1 from Populus tomentosa and its genetic transformation in tobacco

A 3 125 bp cellulose synthase gene, PtoCesA1, which has a 98% identity to PtrCesA1 from Populus tremuloides, was cloned from cDNA prepared from secondary xylem of P. tomentosa. Four anti-expression vectors with different fragments of PtoCesA1, named as pBIPF, pBICC1, pBIPR and pBIBR, were constructed. Some traits of transformed tobacco of pBICC1, pBIPR and pBIBR differed from wild types, such as small leaves, “dwarf” phenotype and thinner xylem and fiber cell walls than wild plants consistent with a loss of cellulose. It indicated that the growth of transgenic tobacco was restrained by the expression of anti-PtoCesA1. Transgenic tobacco was obtained and the contents of cellulose and lignin were analyzed as well as the width and length of fiber cells, and xylem thickness for both transgenic and control plants. Transformed tobacco showed a different phenotype from control plants and it implied that PtoCesA1 was essential for the cellulose biosynthesis in poplar stems. [Supported by the Hi-Tech Research and Development Program of China (863) (2001AA244060 and 2003AA244020) and National Basic Research Program of China (973) (J1999016003)]     

Comparative studies on microstructures and chemical compositions of cell walls of two solid wood floorings

Two common wood flooring materials, taun (Pometia spp.) and cumaru (Dipteryx odorata), were used as investigated objects and comparison was made between the two wood species for their density, microstructure, microfibril angle (MFA), cellulose crystallinity and the main chemical composition. Results showed that the density of cumaru was 0.941 g·cm^?3, significantly larger than that of taun, 0.737 g·cm^?3. The biggest difference of two wood species in microstructures was fiber cells. Fiber cells of cumaru had dense cell walls, almost no cell lumens; while fiber cells of taun had relatively thin cell walls, with apparent cell lumens. The thickness of fiber cell wall of cumaru and taun were 6.80 and 2.82 µm, respectively, and the former is about 2.5 times thicker than the latter. Measured data of MFA indicated that the average MFA of cumaru was 11.7°, smaller than that of taun, 13.4°. The relative crystallinity of cumaru and taun were 54.0 and 50.8%, respectively. The two wood species had the similar holocellulose contents, but the lignin content of cumaru was higher than that of taun, especially that the content of extractive of cumaru was as twice as that of taun.     

Damage characteristics of three boring pests in Artemisia ordosica

The population density and distribution of the three major boring pests, Holcocerus artemisiae, Sphenoptera sp. and Adosopius sp. were studied in their host plant Artemisia ordosica. Results show that the larvae of H. artemisiae mainly bore the rhizome of A. ordosica, but also the larvae of Sphenoptera sp. and Adosopius sp. bore the rhizome of A. tordosica. The adults of Sphenoptera sp. and Adosopius sp. feed on the leaves of A. ordosica as a nutritional supplement. The distribution of the larvae of three pests in their host plant is completely different. H. artemisiae and Sphenoptera sp. are distributed in the whole A. ordosica plant. The newly hatched larvae first feed on the phloem and xylem of stem and then burrow to the roots before the winter of the same year. However, Adosopius sp. is distributed mainly in the roots. The newly hatched larvae move from the phloem to the xylem, and gradually damage the lower part of the trunk. The larvae of the three pests sometimes coexist in a single A. ordosica plant. However, the probability of the coexistence of the three pests is very small. The highest probability of coexistence of two pests was observed in Sphenoptera sp. and H. artemisiae, while the probability of coexistence of Sphenoptera sp. and Adosopius sp. as well as H. artemisiae and Adosopius sp. was smaller. The reasons for coexistence or its avoidance are not only related to the amount of food provided nor the volume of larval living space in a single A. ordosica plant, but also related to the development characteristics of different kinds of larvae and interspecific competition.     

The Imperata grasslands of tropical Asia: area, distribution, and typology

The rehabilitation or intensified use of Imperata grasslands will require a much better understanding of their area, distribution, and characteristics. We generated estimates of the area of Imperata grasslands in tropical Asia, and suggested a typology of Imperata grasslands that may be useful to define the pathways toward appropriate land use intensification. We conclude that the area of Imperata grasslands in Asia is about 35 million ha. This about 4% of the total land area. The countries with the largest area of Imperata grasslands are Indonesia (8.5 million ha) and India (8.0 million ha). Those with the largest proportion of their surface area covered with Imperata are Sri Lanka (23%), the Philippines (17%), and Vietnam (9%). Laos, Thailand, Myanmar, and Bangladesh evidently all have similar proportions of their land area infested with Imperata (about 3 to 4%). Malaysia (< 1%), Cambodia (1%), and the southern part of China (2%) have but a minor proportion of their total land area in Imperata. The species was found widely distributed on the full range of soil orders. It occupied both fertile (e.g. some of the Inceptisols and Andisols) and infertile soils (Ultisols and Oxisols) across a wide range of climates and elevations. Imperata lands fall into four mapping scale-related categories: Mega-grasslands, itmacro-grasslands, meso-grasslands, and micro-grasslands. The mega-grasslands are often referred to as sheet Imperata. They are the large contiguous areas of Imperata that would appear on small-scale maps of say 1:1,000,000. We propose that this basic typology be supplemented with a number of additional components that have a key influence on intensification pathways: land quality, market access, and the source of power for tillage. The typology was applied in a case study of Indonesian villages in the vicinity of Imperata grasslands. We propose an international initiative to map and derive a more complete and uniform picture of the area of the Imperata grasslands. This should include selected studies to understand conditions at the local level. These are critical to build the appreciation of change agents for the indigenous systems of resource exploitation, and how they relate to local needs, values and constraints.     

Characteristics of senescent straw cell walls of dwarf, semidwarf, and normal strains of rice (Oryza sativa) plants

A normal variety of rice (Oryza sativa L.cv. Taichung 65, T65c), its isogenic dwarf line (T65d ₁), and a semidwarf variety of a different line (Oryza sativa L.cv. IR8, IR8) were studied. The results were compared with those of an isogenic dwarf line (Rh _i) of wheat straw, which was previously reported. Expression of the dwarf gene,d ₁, on the chemical composition and the structural features of lignin present in rice internodes differs from that in an isogenic dwarf line of wheat. The differences include the lignin content, total yield of alkaline nitrobenzene oxidation products, and distribution of wall-bound hydroxycinnamic acids. There was, however, no difference in the syringyl/ guaiacyl nuclei (S/V) molar ratio and neutral sugar composition. The lignin composition of rice straw cell walls, particularly that of the dwarf variety, contained more of the condensed structure and fewer syringyl nuclei than lignin in wheat straw cell walls. It is suggested that crosslinking between lignin and polysaccharides by ester-ether bridges via ferulic acid contributes to the mechanical properties of the cell walls of rice straw. Thus the chemical and structural characteristics of lignin in rice straw differ to some extent from those of other temperate grasses, such as wheat (Triticum aestivum) and phalaris (Phalaris aquatica), as reported previously. This can probably be attributed to the water environment of rapidly growing rice seedlings, but it also depends on the genetic variety of the rice plant.     

Distribution of lignin interunit bonds in the differentiating xylem of compression and normal woods of Pinus thunbergii

The lignification process and lignin distribution at different stages of cell wall differentiation in the secondary xylem of compression and normal woods of Pinus thunbergii were investigated by thioacidolysis and subsequent desulfuration. We prepared 50-µm-thick, contiguous tangential sections of pine shoots, cut from the cambial zone through to mature xylem. In compression wood, uncondensed guaiacyl (G) and p-hydroxyphenyl (H) lignins were deposited simultaneously from early to late stages of lignification. The various types of G-G, G-H, and H-H dimers were detected in compression wood, and the ratio of G-H and H-H dimers to total dimers increased as lignification proceeded. In contrast, uncondensed and condensed H units were detected in trace amounts in normal wood. Significant differences in the relative distributions of lignin interunit linkages were not observed between compression and normal woods or between differentiating and mature xylems in either compression or normal woods.Part of this report was presented at the 10th International Symposium on Wood and Pulping Chemistry, Yokohama, June, 1999     

Effect of auxins (IBA and NAA) and season on rooting of juvenile and mature hardwood cuttings of Robinia pseudoacacia and Grewia optiva

Juvenile (2 year old trees) and mature hardwood (15 year old trees) cuttings of Robinia pseudoacacia and Grewia optiva were tested for their capacity to form roots. Cuttings were prepared in spring, monsoon and winter seasons and treated with different concentrations (250, 500 and 750 mg/l) of IBA and NAA. These were planted in a mist chamber maintained at 25±1°C with relative humidity >70%. Juvenile cuttings of both species rooted significantly better than mature hardwood cuttings in all three seasons, and the age effect was more pronounced in auxin treated cuttings. The highest rooting in juvenile (83.3%) and mature (66.6%) cuttings was observed with the NAA (500 mg/l) treatment in R. pseudoacacia during the spring season. In G. optiva, IBA (250 mg/l) in the monsoon season was most effective and yielding a maximum of 80% and 70% rooting in juvenile and mature cuttings, respectively. Auxin treatments also significantly enhanced the number of roots, root length, leaf number and leaf area. Statistical analysis of data revealed that interactions between age, season and treatments were significant at P <0.05 level for R. pseudoacacia and non-significant for G. optiva.     

Structural conversion of the lignin subunit at the cinnamyl alcohol stage in Eucalyptus camaldulensis

The lignin biosynthetic pathway in Eucalyptus camaldulensis was investigated by feeding stems with deuterium-labeled precursor. Pentadeutero[,-D₂ OCD₃] coniferyl alcohol was synthesized and supplied to shoots of E. camaldulensis, and incorporation of the labeled precursor into lignin was traced by gas chromatography-mass spectrometry. In addition to the direct incorporation of labeled precursor into the guaiacyl unit, a pentadeuterium-labeled syringyl unit was detected. This finding indicates that the -deuterium atoms in the hydroxymethyl group of labeled coniferyl alcohol remain intact during modification of the aromatic ring. The relative level of trideuterium-labeled syringyl monomer (the result of conversion via the cinnamic acid pathway) was negligible, suggesting that the pathway at the monolignol stage is used for conversion of exogenously supplied precursor. Our results provide conclusive evidence of a novel alternative pathway for generation of lignin subunits at the monolignol stage even in plants that do not accumulate coniferin in lignifying tissues.     

Structure of xylan from culms of bamboo grass (Sasa senanensis Rehd.)

Xylan prepared from culms of kumaizasa (Sasa senanensis Rehd.), a representative species of bamboo grass, was hydrolyzed with-xylanase ofStreptomyces olivaceoviridis E-86. Four arabinoxylo-oligosaccharides and two glucuronoxylo-oligosaccharides were isolated from the enzymatic hydrolysate of the xylan by chromatography on a charcoal column, a Dowex 1-x8 column, a Toyo-pearl HW-40S column, and a LiChrospher 100 NH₂ column and on preparative paper chromatography. The results of the structural analyses of the saccharides showed that the isolated oligosaccharides had the structures of 3²--l-arabinofuranosyl-xylobiose, 3²--l-arabinofuranosyl-xylotriose, 3²--[-d-xylopyranosyl-(1 2)-l-arabinofuranosyl]-xylobiose, 3³--[-d-xylopyranosyl-(1 2)-l-arabinofuranosyl]-xylotriose, 2³--4-O-methyl-d-glucuronosyl-xylotriose, and 2³--d-glucuronosyl-xylotriose. From the structural analysis of the oligosaccharides derived from the xylan, kumaizasa xylan was concluded to be a kind of arabinoglucuronoxylan having not only stubs of singlel-arabinose and singled-glucuronic acid but also stubs of disaccharide units such as-d-xylopyranosyl-(1 2)-l-arabinofuranose.     

Soft X-ray observation of water distribution in the stem ofCryptomeria japonica D. Don II: Types found in wet-area distribution patterns in transverse sections of the stem

Using soft X-ray photography, two-dimensional observations were made of the water distribution within the green stem ofCryptomeria japonica D. Don. Variations in the distribution pattern of the wet area in the horizontal plane of the lower stem were described. The distribution patterns showed extreme variation among individual trees, with broad wet-area distribution types appearing, namely, the regularly distributed wet area and the irregularly distributed wet area. We defined five basic types of wet-area distribution patterns on the basis of their regularity or irregularity. It was concluded that the between-tree variation in the wet-area distribution causes the between-tree variation in the mean moisture content of the heartwood. The distribution patterns of the wet area were similar for individual trees within each plus-tree clone.Part of this paper was presented at 46th annual meeting of the Japan Wood Research Society at Kumamoto, April 1996     

Analysis of the structure of lignin-carbohydrate complexes by the specific13C tracer method

In the present study the specifically¹³C-enriched lignin precursors of biosynthesis (i.e., coniferin-[side chain–¹³C], coniferin-[side chain-–¹³C] and coniferin-[side chain-–¹³C]) were synthesized and administered exogeneously to ginkgo shoots (Ginkgo biloba L.) to obtain¹³C-enriched lignin-carbohydrate complexes (LCCs). The specifically¹³C-enriched LCCs were isolated from the newly formed xylem of ginkgo shoots administered with the¹³C-enriched precursors and degraded by enzymes. Lignin-rich fractions, so called enzyme-degraded LCCs (EDLCCs), were obtained. By determining their¹³C-NMR spectra, information related to the chemical structure of lignin building units and linkages between phenylpropane units of lignin and carbohydrates were obtained. It was found that these precursors were incorporated in natural lignin successfully. Three lignin-carbohydrates linkages (i.e., ether type, ester type, ketal type) were found at the C -position of the side chain of phenylpropane units in ginkgo LCC. No lignin-carbohydrate bond at the C- or C-position of the lignin side chain was observed in the¹³C-NMR spectra of the¹³C-enriched LCCs. This fact indicates that a specific¹³C tracer technique can be useful in NMR study of the chemical structure of LCCs.Part of this paper was presented at the 5th Pacific Polymer Conference, Kyongju, Korea, October 1997     

Effects of applied gibberellins and uniconazole-P on gravitropism and xylem formation in horizontally positionedFraxinus mandshurica seedlings

The present study deals with the effects of gibberellins (GA₃ GA₄) and uniconazole-P, an inhibitor of gibberellin biosynthesis, on negative gravitropism and xylem formation in the stems of horizontally positioned, 2-year-oldFraxinus mandshurica Rupr. var.japonica Maxim. seedlings. Each growth regulator (100 g) dissolved in 5 l acetone (50%) was applied to the basal node of the current shoot on May 24, 1995. The same treatment was repeated five times weekly until June 28. Five seedlings were used for each treatment. The seedlings were positioned horizontally 24h after the first application on May 25. Within 5 weeks the horizontal stem of control and GA-treated seedlings exhibited negative gravitropism. In contrast, the application of uniconazole-P inhibited negative gravitropic stem bending. The application of GAs increased the number of gelatinous fibers having thickened cell walls on the upper side of stems. The uniconazole-P application decreased xylem cell formation but did not inhibit the formation of gelatinous fibers. These results indicate that not only the differentiation of gelatinous fibers but also xylem increment is important in the negative gravitropism of horizontally positionedF. mandshurica seedlings. These results also suggest that GAs may be involved in xylem cell :formation rather than the differentiation of gelatinous fibers in this species.Part of this research was reported at the 23rd annual meeting of the Plant Growth Regulation Society of America, Calgary, Canada, July 1996     

Modelling wood formation and structure: power and limits of a morphogenetic gradient in controlling xylem cell proliferation and growth

Key message

The emergence of the characteristic tree-ring pattern during xylogenesis is commonly thought to be controlled by a gradient of morphogen (auxin, TDIF peptide...). We show that this hypothesis accounts for several developmental aspects of wood formation, but not for the final anatomical structure.

Context

Wood formation is a dynamic cellular process displaying three generic features: (i) meristematic cell proliferation is restricted to the small cambial zone, preventing exponential xylem radial growth along the growing season; (ii) developmental processes result in a stable zonation of the developing xylem; (iii) the resulting mature wood cells form the typical tree-ring structure made of early and late wood with a gradient of cell sizes, an important trait for wood functioning in trees and for lumber quality. The mechanisms producing these spatial-temporal patterns remain largely unknown. According to the often-cited morphogenetic-gradient hypothesis, a graded concentration profile of a signalling molecule (e.g. auxin, TDIF) controls xylogenesis by providing positional information to differentiating cells.

Aims

We assessed the predictions of the morphogenetic-gradient theory.

Methods

We developed a computational model of wood formation implementing hypotheses on how a morphogen flows through the developing xylem and controls cell division and growth and we tested it against data produced by studies monitoring wood formation in conifers.

Results

We demonstrated that a morphogenetic gradient could indeed control xylem radial growth and wood-forming tissue zonation. However, it failed to explain the pattern of final cell sizes observed in tree-rings. We discussed the features that candidate additional regulatory mechanisms should meet.

     

Biological activity of extracts fromCupressus lusitanica cell culture

Ethyl acetate extracts ofCupressus lusitanica suspension cell cultures were examined for their biological activities (viz., tyrosinase inhibitory, antioxidant, and antimicrobial activities). The extract from elicitor-treated cells showed all of the biological activities, whereas the extract from cultures without elicitor was not bioactive to a discernible extent. The biological activities shown by the cell culture extracts were almost solely accounted for by-thuj aplicin contained in the extracts. These results suggest that the ethyl acetate extract ofC. lusitanica cells treated with the elicitor is a valuable bioactive source without isolation or purification of-thujaplicin.     

The effect of competition on individual tree basal area growth in mature stands of Pinus cooperi Blanco in Durango (Mexico)

In this paper, we evaluated how well-selected distance-dependent and distance-independent competition indices explain individual tree basal area growth of trees, growing in mature and even-aged stands of Pinus cooperi Blanco. A total of 18 competition measures were analyzed of which six do not need tree location (distance-independent) and 12 that utilize tree location (distance-dependent). The competition situation of a stand and/or an individual tree was studied using 11 different competitor selection methods. The mean square error reduction relative to no-competition was used to judge the performance of each competition index. It was found that the best distance-independent competition indices performed as well as the best distance-dependent competition indices. It was concluded that the BALMOD-index would be a good competition index to be incorporated into further individual tree basal area growth models for the study area.

巨桉EXP基因家族的生物信息学分析

[目的]本研究有助于了解EXP基因家族的基本特征,为深入研究其功能搭建平台。[方法]本研究对从巨桉(Eucalyptus grandis Hill)中筛选出35个EXP基因家族成员(Egr EXP1 Egr EXP35),利用生物信息学方法对其基因特征与表达模式进行综合分析。[结果]巨桉EXP基因分布在8条染色体之上,EXP蛋白均定位在细胞质膜上发挥作用,大多数的家族成员具有信号肽。巨桉EXP编码的蛋白质由α-螺旋、延伸链、无规卷曲、β-转角组成。进化分析结果表明,巨桉EXP蛋白与毛果杨(Populus trichocarpa) EXP蛋白的进化关系接近。35个巨桉EXP基因在巨桉未成熟木质部、成熟叶片、韧皮部、茎尖、木质部以及幼叶组织中表达模式存在显著差异。[结论]EXP基因家族各成员的表达模式不同,Egr EXP17、Egr EXP18可能在巨桉木材形成过程中起重要作用。     

Water status of hinoki cypress, Chamaecyparis obtusa, attacked by secondary woodboring insects after typhoon strike

We estimated the water status of six 31-year-old hinoki cypress (Chamaecyparis obtusa) trees that were struck by a large typhoon. Measurements were made of the trunk water-conduction area of xylem, leaf water potentials, and diurnal changes in trunk diameters. The secondary woodboring insects, Callidiellum rufipenne and Ovalisia vivata, on the trees were captured by the sticky-trap banding method. In trees on which these wood borers were captured, water conduction areas were reduced, leaf water potentials were lower, and trunk diameter changes (R) fluctuated during the day, suggesting that the trees had been damaged by the typhoon and were under water stress. The secondary woodboring insects attacked the water-stressed trees.