Search

Fibrovascular bundles (FVB) are a cell tissue in monocot plants composed of fibers, xylem, phloem, and axial parenchyma, binding to form bundles. FVB has the potential to be used as a raw material for composite boards. However, it has several weaknesses, including low strength and surface properties that do not support gluing. This study therefore aimed to investigate the effect of a combined NaOH + Na2SO3 treatment on the physical, chemical, and mechanical properties changes in S. sumatrana Becc. fronds. After separation from the fronds, the fibrovascular bundles were separately immersed in several conditions of NaOH + Na2SO3, for 30 min and 60 min, then washed and dried. Subsequently, the tissues were evaluated using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and tensile strength tests. The pits and deposits of the fibrovascular bundles completely collapsed, degraded, and swelled after treatment with 1 M NaOH + 2% Na2SO3. The treatment resulted in the eventual elimination of hemicelluloses and lignins. Separation of the elementary fiber on the fibrovascular bundles occurred at higher concentration treatments. In addition, the strength of the tissue improved after 60 min of immersion in a mixture of 1% NaOH and 0.2% Na2SO3. Based on these results, treatment with a combination of 1% NaOH + 0.2% Na2SO3 was concluded to change the chemical and physical properties as well as improve the mechanical properties of the fibrovascular bundles.

Situs Liyangan yang berada di Dusun Liyangan Desa Purbosari Kecamatan Ngadirejo Kabupaten Temanggung selama 1 dasawarsa ini telah dilakukan penelitian oleh Balai Arkeologi Provinsi D.I. Yogyakarta. Hasil-hasil penelitian itu memberikan informasi mengenai ragam data, kronologi, dan aspek keruangan Situs Liyangan. Salah satu ragam data yang akan dibahas dalam artikel ini adalah data organik yang berasal pollen dan sisa arang. Tujuan penulisan artikel ini adalah memberikan informasi mengenai keanekaragaman tanaman di situs liyangan. Metode yang digunakan dalam artikel ini merupakan kajian desk study berupa kajian referensi hasil penelitian yang telah dilakukan di Situs Liyangan. Hasil kajian desk study keanekaragaman tanaman di situs liyangan diperoleh informasi bahwa Identifikasi sisa-sisa tanaman yang diperoleh di situs Liyangan terdiri atas vegetasi berjenis rumput-rumputan, semak, dan pohon. Keberagaman jenis tanaman yang dijumpai di Situs Liyangan ini menunjukkan makna karakteristik Situs Liyangan sebagai lokasi penanda kesuburan wilayah.

This study aimed to investigate the ash content and concentrations of inorganic elements present in the stem of Acacia mangium. The tree samples (24 years) were collected from five different provenances (Sidei, West of Morehead, Daintree, Ellerbeck, and El Arish). Meanwhile, the disc samples were obtained from the trunk of each tree on the lower parts. The samples were collected from four radial positions (bark, sapwood, outer heartwood, inner heartwood), and the ash and insoluble acid contents were determined. Furthermore, the concentration of 5 elements (Ca, Mg, Fe, Mn, K, and Na) was measured by Atomic Absorption Spectrophotometry (AAS). The interaction of provenance and radial position factors affected ash and potassium contents. Also, acid insoluble ash and calcium contents showed a provenance factor effect. The barks obtained from the tree samples contained the highest concentrations of ash content and most of the elements. The wood and bark of El-Arish provenance showed the lowest (0.50~0.72%) and highest levels (4.75%) of ash content respectively. Furthermore, the highest amount of insoluble acid ash (3075 ppm) and calcium (4513 ppm) content was also measured in samples of El-Arish provenance, and radial position factor was a significant source of variation for Ca, Mg, Na, and Mn concentrations. Except Mg, the inner and outer portions of the heartwood mostly showed no significant difference in unprecedented element concentrations. Ash content was positively correlated with Ca in sapwood (r=0.39) and Mn in bark (r=0.54). In addition, moderate correlations were observed between Mg and Ca in heartwood (r=0.63) and bark (r=0.54) tissues. For ash and silica content, the comparatively low concentration on samples from El-Arish provenance are good options to improve wood quality for breeding programs.

Rahmawati RB, Widiyatno, Hardiwinoto S, Budiadi, Nugroho WD, Wibowo A, Rodiana D. 2022. Effect of spacing on growth, carbon sequestration, and wood quality of 8-year-old clonal teak plantation for sustainable forest teak management in Java Monsoon Forest. Biodiversitas 23: 4180-4188. Lowland monsoon forest dominated by teak was one of the tropical forest types that can contribute to producing wood production, carbon storage, reduction of emissions, and other ecosystem services. Increasing teak forest productivity could be obtained through teak breeding to get superior teak clones with high diameter growth. Thus, spacing is an important consideration for optimizing the growth, carbon sequestration, and wood properties of teak. However, the study of the growth, carbon sequestration, and wood quality of teak was conducted separately. This research used a selected teak clone aged 8 years with RCBD design with 4 blocks as replications. There were four different spacing as treatments, namely 10 m x 2 m, 8 m x 2 m, 6 m x 2 m, and 3 m x 3 m. The results showed that spacing was a significant effect on DBH, tree height, bole height, carbon sequestration, and volume of teak clones aged 8 years. On the other hand, spacing didn’t significantly affect the physical and mechanical properties of wood. The wood quality test showed that the 6 m x 2 m spacing had high values of bending strength and compressive strength parallel. The highest percentage of heartwood was at a narrow spacing of 6 m x 2 m and did not differ significantly with wide spacing. This indicated that wide spacing was beneficial in terms of teak growth, but wide spacing didn’t significantly affect on wood quality of the teak.

Hakim L, Widyorini R, Nugroho WD, Prayitno TA. 2021. Radial variability of fibrovascular bundle properties of salacca (Salacca zalacca) fronds cultivated on Turi Agrotourism in Yogyakarta, Indonesia. Biodiversitas 22: 3594-3603. Fibrovascular bundles have properties variability not only based on species and varieties but also parts of species. This study, therefore, aims to characterize the FVB fundamental properties (anatomical, chemical, physical and mechanical) of Salacca zalacca (Gaertn.) Voss fronds, based on radial direction. The salacca fronds were divided into three parts, outer, middle as well as inner positions. Then the FVB's anatomical and physical properties were observed by light microscope and gravimetry analysis, respectively. Meanwhile, the variability of chemical and mechanical properties was investigated based on the ASTM standard. According to the results, the outer position has a higher variability of diameter, density, cellulose, lignin, and mechanical properties than the inner position, but has a lower hemicellulose value than the middle and inner position. Furthermore, the relationships between the anatomical, physical, chemical, and mechanical properties were discovered to form a pattern where increasing the mechanical properties is influenced by density and ratio vascular tissue area to total transverse area. Based on the results, the fibrovascular bundle of S. zalacca frond was concluded to possess anatomical, physical, chemical, and mechanical properties variability on the radial direction. There was a correlation between anatomical properties and mechanical properties.

This study focused on the effect of an extractive treatment and the application of citric acid on the properties of particleboard made from Salacca frond. In general, extractives have a negative effect on the bondability of synthetic resin. However, the effect of extractives on the bonding mechanism of citric acid as the biobased adhesive is unclear. Unextracted and extracted Salacca frond were used as the raw materials. A hot water extractive treatment was conducted by boiling the particles for 2 h. The boards were manufactured under the following conditions: citric acid content of 0%; 10%; 20% weight percent (wt%), pressing temperature of 180 °C, and pressing time of 10 min. The target density was set at 0.8 g cm-3. The results showed that the addition of citric acid resulted in an increase in the physical and mechanical properties of the particleboard. Interestingly, when a 20% citric acid content was applied, there were no siginificant differences in the physical or mechanical properties of the particleboards made from unextracted and extracted particles. Based on these results, it was concluded that when citric acid is used as adhesive, the hot-water extractive treatment of Salacca frond is not needed.

Temperature is an important factor for the cambial growth in temperate trees. We investigated the way daily temperatures patterns (maximum, average and minimum) from late winter to early spring affected the timing of cambial reactivation and xylem differentiation in stems of the conifer Chamaecyparis pisifera. When the daily temperatures started to increase earlier from late winter to early spring, cambial reactivation occurred earlier. Cambium became active when it achieves the desired accumulated temperature above the threshold (cambial reactivation index; CRI) of 13 °C in 11 days in 2013 whereas 18 days in 2014. This difference in duration required for achieving accumulated temperature can be explained with the variations in the daily temperature patterns in 2013 and 2014. Our formula for calculation of CRI predicted the cambial reactivation in 2015. A hypothetical increase of 1–4 °C to the actual daily maximum temperatures of 2013 and 2014 shifted the timing of cambial reactivation and had different effects on cambial reactivation in the two consecutive years because of variations in the actual daily temperatures patterns. Thus, the specific annual pattern of accumulation of temperature from late winter to early spring is a critical factor in determining the timing of cambial reactivation in trees.

The fibrovascular bundle (FVB) in palm plants consists of fiber and vascular tissue. Geometrically, it is a long fiber that can be used as an oriented board raw material. This research aimed to examine the performance of citric acid-bonded orientation boards from modified FVB salacca frond under NaOH + Na2SO3 treatment and the bonding mechanism between the modified FVB frond and citric acid. The results showed that changes in the chemical composition of FVB have a positive effect on the contact angle and increase the cellulose crystallinity index. Furthermore, the mechanical properties of the oriented board showed that 1% NaOH + 0.2% Na2SO3 with 60 min immersion has a higher value compared to other treatments. The best dimension stability was on a board with the modified FVB of 1% NaOH + 0.2% Na2SO3 with 30 and 60 min immersion. The bonding mechanism evaluated by FTIR spectra also showed that there is a reaction between the hydroxyl group in the modified FVB and the carboxyl group in citric acid. This showed that the modified combination treatment of NaOH+Na2SO3 succeeded in increasing the mechanical properties and dimensional stability of the orientation board from the FVB salacca frond.

A better understanding of the influence of environmental conditions on wood formation should help to improve the radial growth of trees and to prepare for climate change. The cambial activity of trees is associated with seasonal cycles of activity and dormancy in temperate zones. The timing of cambial reactivation in early spring and dormancy in autumn plays an important role in determination of the cambial growth and the environmental adaptivity of temperate trees. This review focuses on the temperature regulation of the timing of cambial reactivation and xylem differentiation and highlights recent advances of bud growth in relation to cambial activity of temperate trees. In addition, we discuss relationships between the timing of cambial reactivation, start of xylem differentiation and changes in levels of storage materials to identify the source of the energy required for cell division and differentiation. We also present a summary of current understanding of the effects of rapid increases and decreases in temperature on cambial activity, by localized heating and cooling, respectively. Increases in temperature from late winter to early spring influence the physiological processes that are involved in the initiation of cambial reactivation and xylem differentiation both in localized heated stems and under natural conditions. Localized cooling has a direct effect on cell expansion, the thickening of walls of differentiating tracheids, and the rate of division of cambial cells. A rapid decrease in temperature of the stem might be the critical factor in the control of latewood formation and the cessation of cambial activity. Therefore, temperature is the main driver of cambial activity in temperate trees and trees are able to feel changes in temperature through the stem. The climate change might affect wood formation in trees.

Eucalyptus pellita F. Muell is one of pulp woods that is being developed through breeding plantation programs in Indonesia. The research aimed at exploring the chemical and morphological characteristics of fiber, and to determine the rank of plus trees from 4 provenances based on the suitability for pulps. The materials included the plus trees of E. pellita (9 years) from the 2nd generation of progeny tests in Pelaihari, South Borneo. Wood properties under investigation included the chemical properties and morphological fiber characteristics (fiber dimensions and its derived properties). In the present study, data were analyzed using descriptive statistic, Analytic Hierarchy Process (AHP) and Pearson`s correlation. Results showed that the chemical properties of E. pellita, i.e. the contents of ethanol-toluene extractives, hot water soluble extractives, holocellulose, alphacelullose, and lignin were , , , , and , respectively. The average values of wood fiber morphology were mm (fiber length), (fiber diameter), of (lumen diameter), (fiber wall thickness), (Runkel ratio), (Luce`s shape factor), (slenderness ratio) and (solids factor). The AHP scoring rank indicated that the best individuals were 28.4.3.28 (Kiriwo Utara), 12.1.5.28 (North Kiriwo), 19.11.5.45 (Serisa Village), 3.8.4.9 (South Kiriwo), and 6.6.3.15 (South Kiriwo). Pearson correlation analysis showed significant correlations between the levels of fiber length with alpha-cellulose content (r

Elucidation of the mechanism of adsorption of particles suspended in the gas-phase (aerosol) to the outer surfaces of leaves provides useful information for understanding the mechanisms of the effect of aerosol particles on the growth and physiological functions of trees. In the present study, we examined the localization of artificially deposited sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica, a typical Japanese coniferous tree species, by field-emission scanning electron microscopy. The clusters (aggregates) of carbon-based particles were deposited on the needle surface regions where epicuticular wax crystals were sparsely distributed. By contrast, no clusters of the particles were found on the needle surface regions with dense distribution of epicuticular wax crystals. Number of clusters of carbon-based particles per unit area showed statistically significant differences between regions with sparse epicuticular wax crystals and those with dense epicuticular wax crystals. These results suggest that epicuticular wax crystals affect distribution of carbon-based particles on needles. Therefore, densely distributed epicuticular wax crystals might prevent the deposition of sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica to retain the function of stomata.

We observed the formation of latewood tracheids with narrow diameters and thick walls and the disappearance of stored starch around the cambium on the locally heated region of stems in evergreen conifer Chamaecyparis pisifera during winter cambial dormancy. Wood formation is controlled by cambial cell division, which determines the quantity and quality of wood. We investigated the factors that control cambial activity and the formation of new tracheids in locally heated stems of the evergreen conifer Chamaecyparis pisifera. Electric heating tape was wrapped around one side of the stem, at breast height, of two trees in 2013 and two in 2014. Pairs of stems were locally heated in winter, and small blocks were collected from heated and non-heated regions of stems. Cambial activity and levels of stored starch around the cambium were investigated by microscopy. Cambial reactivation and xylem differentiation occurred earlier in heated than in non-heated regions. New cell plates were formed after 14–18 days of heating. After a few layers of tracheids with large diameters and thin walls had formed, cell division and cell enlargement during differentiation were inhibited. Tracheids with narrow diameters and thick walls, defining those as latewood, were formed near the cambium, and finally, four to six layers of tracheids were induced. After cambial reactivation, amounts of stored starch started to decrease and starch disappeared completely from phloem and xylem cells that were located near the cambium during the differentiation of heated regions. Our results suggest that an increase in temperature induces the conversion of stored starch to soluble sugars for continuous cambial cell division and earlywood formation. By contrast, a shortage of stored starch might be responsible for inhibition of cambial activity and induction of the formation of latewood tracheids.

Premise Cambial activity in some tropical trees varies intra-annually, with the formation of xylem rings. Identification of the climatic factors that regulate cambial activity is important for understanding the growth of such species. We analyzed the relationship between climatic factors and cambial activity in four tropical hardwoods, Acacia mangium, Tectona grandis, Eucalyptus urophylla, and Neolamarckia cadamba in Yogyakarta, Java Island, Indonesia, which has a rainy season (November-June) and a dry season (July-October). Methods Small blocks containing phloem, cambium, and xylem were collected from main stems in January 2014, October 2015 and October 2016, and examined with light microscopy for cambial cell division, fusiform cambial cells, and expanding xylem cells as evidence of cambial activity. Results During the rainy season, when precipitation was high, cambium was active. By contrast, during the dry season in 2015, when there was no precipitation, cambium was dormant. However, in October 2016, during the so-called dry season, cambium was active, cell division was conspicuous, and a new xylem ring formation was initiated. The difference in cambial activity appeared to be related to an unusual pattern of precipitation during the typically dry months, from July to October, in 2016. Conclusions Our results indicate that low or absent precipitation for 3 to 4 months induces cessation of cambial activity and temporal periodicity of wood formation in the four species studied. By contrast, in the event of continuing precipitation, cambial activity in the same trees may continue throughout the year. The frequency pattern of precipitation appears to be an important determinant of wood formation in tropical trees.

Non-woody fiber is a sustainable resource for composite products. In this study, salacca frond was used as a raw material, and the effects of citric acid-maltodextrin composition ratio, pressing temperature, and pressing method were investigated. The boards were manufactured under the conditions as follows: single-step press method, adhesive contents 20 wt%, pressing temperature (180 to 200 °C), and adhesive composition of citric acid/ maltodextrin (100/0; 87.5/12.5; 75/25; 62.5/37.5; 50/50 wt%). A three-step press cycle method was also applied to reduce the pre- drying time before hot pressing. The total pressing time was 10 min, and the breathing stage was applied at various times after the starting time. The results showed that salacca frond is a potential material for composite board. The addition of maltodextrin in certain ratios improved the mechanical properties. The mechanical properties of board prepared using citric acid/maltodextrin satisfied the requirement of the JIS A 5908 type 13 (2003) standard. Infrared analyses indicated that carboxyl groups of citric acid react with the hydroxyl groups of the maltodextrin and salacca frond. Furthermore, the three-step press cycle method was more effective than the single-step press method. Adding a breathing stage improved the quality of citric acid/maltodextrin bonded composite board.

Fiber morphology and basic characteristics of Legi bamboos (Gigantochloa atter) growing on Yogyakarta were studied considering their age and height positions in the culms. Culms of 4, 16, and 40 months were har- vested, and their total lengths were measured. The length, diameter, and wall thickness of each internode were measured. All the sample culms were divided into three different parts along the height, and their fiber dimension and physical properties were observed. The data obtained were analyzed by analysis of variance. The results showed that the culms had a diameter of 5.8 to 10.8 cm. The lowest internodes always showed the shortest length and the thickest wall. The culms had an average fiber length of 2.41 mm and Runkel ratio of 0.61. Fiber length was affected by the height, while fiber diameter, lumen diameter, and fiber wall thickness were affected significantly by the age of the culms. The culms had high green moisture content (GMC) of 157.89%, and basic density (BD) of 456.67 kg.m -3 , a total longitudinal shrinkage of 0.35%, and relatively low R/T shrinkage ratio. The interactions between age and height were affected GMC and BD.

Background and aims In response to a gravitational stimulus, angiosperm trees generally form tension wood on the upper sides of leaning stems in order to reorientate the stems in the vertical direction. It is unclear whether the angle of inclination from the vertical affects tension wood formation. This study was designed to investigate negative gravitropism, tension wood formation and growth eccentricity in Acacia mangium seedlings inclined at different angles. Methods Uniform seedlings of A. mangium were artificially inclined at 30°, 45°, 60° and 90° from the vertical and harvested, with non-inclined controls, 3 months later. We analysed the effects of the angle of inclination on the stem recovery angle, the anatomical features of tension wood and radial growth. Key results Smaller inclination angles were associated with earlier stem recovery while stems subjected to greater inclination returned to the vertical direction after a longer delay. However, in terms of the speed of negative gravitopism towards the vertical, stems subjected to greater inclination moved more rapidly toward the vertical. There was no significant difference in terms of growth eccentricity among seedlings inclined at different angles. The 30°-inclined seedlings formed the narrowest region of tension wood but there were no significant differences among seedlings inclined at 45°, 60° and 90°. The 90°-inclined seedlings formed thicker gelatinous layers than those in 30°-, 45°- and 60°-inclined seedlings. Conclusion Our results suggest that the angle of inclination of the stem influences negative gravitropism, the width of the tension wood region and the thickness of gelatinous layers. Larger amounts of gelatinous fibres and thicker gelatinous layers might generate the higher tensile stress required for the higher speed of stem-recovery movement in A. mangium seedlings.

The anatomical characteristics and density of wood were examined in 23-year-old Acacia mangium trees that had been planted in Yogyakarta, Indonesia. The seeds had been collected from trees of five different provenances. The distance from the pith of the boundary between juvenile and mature wood was also examined to clarify the maturity of the wood. Lengths of wood fibers near the pith and the distance from the pith of the boundary between juvenile and mature wood differed significantly among provenances. By contrast, other anatomical characteristics of the wood such as fiber wall area, fiber wall thickness, fiber diameter, vessel lumen area, vessel diameter, vessel frequency and wood density did not differ significantly among provenances. Wood density was strongly correlated with the area of fiber walls. Our observations suggest that Sidei and Daintree might be more appropriate provenances among those examined for the Acacia mangium tree-breeding programs in Indonesia that are aimed at improving wood quality, because these provenances are associated with longer initial wood fibers and narrower juvenile areas than the other provenances studied.

Wood is produced by the cambium of stems of trees. The cambial activity of trees exhibits seasonal cycles of activity and dormancy in temperate and cool zones. The timing of cambial reactivation in the early spring plays an important role in the determination of the quantity of wood and the environmental adaptivity of trees. Numerous studies have demonstrated that the cambial reactivation is controlled by the temperature of stems. As soon as cambial cells lose the ability to divide, they start to differentiate into secondary xylem cells. Finally, cell death occurs in secondary xylem cells, but its timing is different among the types and positions of cells. During formation of the secondary wall in tracheids or wood fibers, the cellulose microfibrils change their orientation progressively to form thick cell walls with a highly organized structure. In addition, secondary xylem cells form modifications of the cell wall, such as helical thickening and pits, by the localized deposition of cellulose microfibrils. There are considerable evidences that the dynamics of cortical microtubules are closely related to the orientation and localization of newly deposited cellulose microfibrils in the differentiating secondary xylem cells, indicating that microtubules control the structure of cell wall, thereby wood quality.

BACKGROUND AND AIMS In temperate regions, trees undergo annual cycles of cambial growth, with periods of cambial activity and dormancy. Environmental factors might regulate the cambial growth, as well as the development of cambial derivatives. We investigated the effects of low temperature by localized cooling on cambial activity and latewood formation in two conifers, Chamaecyparis obtusa and Cryptomeria japonica. METHODS A plastic rubber tube that contained cooled water was wrapped around a 30-cm-wide portion of the main stem of Chamaecyparis obtusa and Cryptomeria japonica trees during seasons of active cambium. Small blocks were collected from both cooled and non-cooled control portions of the stems for sequential observations of cambial activity and for anatomical measurements of cell morphology by light microscopy and image analysis. KEY RESULTS The effect of localized cooling was first observed on differentiating tracheids. Tracheids narrow in diameter and with significantly decreased cambial activity were evident 5 weeks after the start of cooling in these stems. Eight weeks after the start of cooling, tracheids with clearly diminished diameters and thickened cell walls were observed in these stems. Thus, localized low temperature induced narrow diameters and obvious thickening of secondary cell walls of tracheids, which were identified as latewood tracheids. Two months after the cessation of cooling, a false annual ring was observed and cambium became active again and produced new tracheids. In Cryptomeria japonica, cambial activity ceased earlier in locally cooled portions of stems than in non-cooled stems, indicating that the cambium had entered dormancy sooner in the cooled stems. CONCLUSIONS Artificial cooling of stems induced latewood formation and cessation of cambial activity, indicating that cambium and its derivatives can respond directly to changes in temperature. A decrease in the temperature of the stem is a critical factor in the control of cambial activity and xylem differentiation in trees.

BACKGROUND AND AIMS When the orientation of the stems of conifers departs from the vertical as a result of environmental influences, conifers form compression wood that results in restoration of verticality. It is well known that intercellular spaces are formed between tracheids in compression wood, but the function of these spaces remains to be clarified. In the present study, we evaluated the impact of these spaces in artificially induced compression wood in Chamaecyparis obtusa seedlings. METHODS We monitored the presence or absence of liquid in the intercellular spaces of differentiating xylem by cryo-scanning electron microscopy. In addition, we analysed the relationship between intercellular spaces and the hydraulic properties of the compression wood. KEY RESULTS Initially, we detected small intercellular spaces with liquid in regions in which the profiles of tracheids were not rounded in transverse surfaces, indicating that the intercellular spaces had originally contained no gases. In the regions where tracheids had formed secondary walls, we found that some intercellular spaces had lost their liquid. Cavitation of intercellular spaces would affect hydraulic conductivity as a consequence of the induction of cavitation in neighbouring tracheids. CONCLUSIONS Our observations suggest that cavitation of intercellular spaces is the critical event that affects not only the functions of intercellular spaces but also the hydraulic properties of compression wood.

Wood is one of the most important renewable natural resources. The quantity and quality of wood are determined by the activity of cambium, xylem differentiation, and cell death. This chapter provides protocols for visualizing the structure of cambium and secondary xylem cells, dynamic changes in cortical microtubules (MTs) and cell organelles, such as nuclei and vacuoles, and the detection of fluorescence spectra of autofluorescence of cell walls and nuclear DNA fragmentation by confocal laser scanning microscopy (CLSM) with fluorescent dye. CLSM is a powerful tool for the construction of three-dimensional (3D) images of the process of wood formation in trees.

Gibberellin stimulates negative gravitropism and the formation of tension wood in tilted Acacia mangium seedlings, while inhibitors of gibberellin synthesis strongly inhibit the return to vertical growth and suppress the formation of tension wood. To characterize the role of gibberellin in tension wood formation and gravitropism, this study investigated the role of gibberellin in the development of gelatinous fibres and in the changes in anatomical characteristics of woody elements in Acacia mangium seedlings exposed to a gravitational stimulus.Gibberellin, paclobutrazol and uniconazole-P were applied to the soil in which seedlings were growing, using distilled water as the control. Three days after the start of treatment, seedlings were inclined at 45 ° to the vertical and samples were harvested 2 months later. The effects of the treatments on wood fibres, vessel elements and ray parenchyma cells were analysed in tension wood in the upper part of inclined stems and in the opposite wood on the lower side of inclined stems.Application of paclobutrazol or uniconazole-P inhibited the increase in the thickness of gelatinous layers and prevented the elongation of gelatinous fibres in the tension wood of inclined stems. By contrast, gibberellin stimulated the elongation of these fibres. Application of gibberellin and inhibitors of gibberellin biosynthesis had only minor effects on the anatomical characteristics of vessel and ray parenchyma cells.The results suggest that gibberellin is important for the development of gelatinous fibres in the tension wood of A. mangium seedlings and therefore in gravitropism.