Sri Nugroho Marsoem

Gibberellin is required for the formation of tension wood and stem gravitropism in Acacia mangium seedlings

BACKGROUND AND AIMS Angiosperm trees generally form tension wood on the upper sides of leaning stems. The formation of tension wood is an important response to gravitational stimulus. Gibberellin appears to be involved in the differentiation of secondary xylem, but it remains unclear whether gibberellin plays a key role in the formation of tension wood and plant gravitropism. Therefore, a study was designed to investigate the effects of gibberellin and of inhibitors of the synthesis of gibberellin, namely paclobutrazole and uniconazole-P, on the formation of tension wood and negative stem gravitropism in Acacia mangium seedlings. METHODS Gibberellic acid (GA(3)), paclobutrazole and uniconazole-P were applied to seedlings via the soil in which they were growing. Distilled water was applied similarly as a control. Three days after such treatment, seedlings were tilted at an angle of 45° from the vertical, and samples of stems were collected for analysis 2 weeks, 2 months and 6 months after tilting. The effects of treatments on the stem recovery degree (Rº) were analysed as an index of the negative gravitropism of seedlings, together the width of the region of tension wood in the upper part of inclined stems. KEY RESULTS It was found that GA(3) stimulated the negative gravitropism of tilted seedling stems of A. mangium, while paclobutrazole and uniconazole-P inhibited recovery to vertical growth. Moreover, GA(3) stimulated the formation of tension wood in tilted A. mangium seedlings, while paclobutrazole and uniconazole-P strongly suppressed the formation of tension wood, as assessed 2 weeks after tilting. CONCLUSIONS The results suggest that gibberellin plays an important role at the initial stages of formation of tension wood and in stem gravitropism in A. mangium seedlings in response to a gravitational stimulus.

Radial variations in the anatomical characteristics and density of the wood of Acacia mangium of five different provenances in Indonesia

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.

Effect of the lateral growth rate on wood properties in fast-growing hardwood species

We investigated the feasibility of using several fast-growing tropical or subtropical hardwood species for timber production by measuring key wood qualities in relationship to the high rates of lateral growth. The trees tested were sampled from even-aged plantations of Acacia mangium, A. auriculiformis, hybrid Acacia (A. mangium × A. auriculiformis), Eucalyptus grandis, E. globulus, and Paraserianthes falcataria (Solomon and Java origin) that had already reached commercial harvesting age. The released strain of the surface growth stress (RS), xylem density (XD), microfibril angle (MFA), and fiber length (FL) were measured at the outermost part of the xylem at breast height in each tree. Results were then compared to the lateral growth rate (radius/age) at breast height, which provides a relative indicator of the amount of tree growth per year. Our findings indicated that RS was constant, regardless of lateral growth rate in each species. Similar results were observed for XD, MFA, and FL, with a few exceptions, suggesting that high growth rates do not intrinsically affect the wood properties of fast-growing tropical or subtropical species that have reached harvesting age. However, special attention must be paid to patterns of xylem maturation when developing plantations of such species.

Growth characteristics, stress-wave velocity, and Pilodyn penetration of 15 clones of 12-year-old Tectona grandis trees planted at two different sites in Indonesia

Tree improvement programs for teak (Tectona grandis) have mainly focused on breeding of trees with superior growth characteristics. However, improvement in wood quality should be included in breeding programs for high yield and high quality timber. In the present study, growth characteristics [stem diameter (D), tree height (H), and bole volume (V)], stress-wave velocity (SWV), and Pilodyn penetration (Py) were measured for 15 clones of 12-year-old teak trees planted at two different sites in Indonesia to clarify the variations in tree growth characteristics, SWV, and Py among clones, their repeatability, interaction between genotype and environment, and correlations between measured characteristics. Significant differences of all measured characteristics were found among 15 clones at both sites. Their repeatability showed relatively moderate to high values in both sites. These results indicate that these characteristics are closely related to genetic factors. Significant interaction between genotype and environment was found in all measured characteristics. In addition, SWV and Py showed lower interaction between genotype and environment than growth characteristics. No significant correlation was found between growth characteristics and SWV. These results suggest that wood properties and growth characteristics of teak trees can be improved by application of an appropriate tree breeding program.

Gibberellin mediates the development of gelatinous fibres in the tension wood of inclined Acacia mangium seedlings.

BACKGROUND AND AIMS 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. METHODS 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. KEY RESULTS 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. CONCLUSIONS 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.

Basic properties of Acacia mangium and Acacia auriculiformis as a heating fuel

We examined the potential bioenergy of two Acacia wood species, Acacia mangium (Am) and Acacia auriculiformis (Aa). The objectives of this study were to assess the basic properties (anatomical, physical, and chemical-related properties) and to compare bioenergy potentials among these two Acacia species from Indonesia. Six 3-year-old trees were randomly selected from plantation forest on South Kalimantan. Statistically, no significant difference was found in calorific value between the two species of Acacia or position in the stem. The calorific values ranged from 16.6-17.5 kJ/g in the Am species and from 16.8-17.4 kJ/g in the Aa species. Based on these properties, both of these species have the same potency as a heating fuel resource. The top (T) position which usually has a smaller diameter and lower economic value may be used as a heating fuel source with its potency of the calorific value which is equal to the other parts of the stem. The calorific value in both Acacia wood was influenced by vessel fre...

The Effects of Radial Growth Rate on Wood Properties and Anatomical Characteristics and an Evaluation of the Xylem Maturation Process in a Tropical Fast-Growing Tree Species, Gmelina arborea

Abstract The aim of this study was to evaluate the effects of radial growth on wood properties and anatomical characteristics and to clarify the xylem maturation process in Gmelina arborea. Stem diameter, tree height, and stress-wave velocity were investigated for 54 5-year-old G. arborea trees planted in Indonesia. In addition, radial variations of wood properties (basic density and compressive strength parallel to the grain in green condition) and anatomical characteristics (fiber and vessel morphologies) were investigated for nine trees selected from three different radial growth categories (fast, medium, and slow growing). Stem diameter was positively significantly correlated with stress-wave velocity and compressive strength parallel to the grain in green condition. In addition, compressive strength and anatomical characteristics, except for wood fiber diameter, differed significantly among the radial growth categories. Radial variations of the wood properties and anatomical characteristics gradually...

Ozone treatment of spent medium from Auricularia polytricha cultivation for enzymatic saccharification and subsequent ethanol production

We examined the enzymatic saccharification and ethanol fermentation of the spent media (SMs) from Auricularia polytricha cultivation using wood meals of Falcataria moluccana, Shorea sp., and Tectona grandis. Although the hydrolysis weight decrease and reducing sugar yield were higher in SM of F. moluccana, the ethanol yield was higher in SM of Shorea sp. Ozone treatment of SM further increased the hydrolysis weight decrease, reducing sugar, and ethanol yields in Shorea sp. These results indicate that SM of A. polytricha is a suitable biomass material to produce fermentable sugars for ethanol production, and that ozone treatment is a suitable method for increasing the ethanol yield.

Radial variation of wood properties in Neolamarckia cadamba trees from an East Java community forest

Radial variations in wood properties, cell morphologies and cell proportions were investigated for nine 4-year-old Neolamarckia cadamba trees planted in a community forest in East Java, Indonesia. The relationships between stem diameter and wood properties, cell morphologies or cell proportions were determined to ascertain the effects of stem diameter on these properties. In the radial variations, almost all of the wood properties, cell morphol- ogies and cell proportion in N. cadamba were changed at around 4 to 6 cm distance from the pith, except for fibre diameter, and the proportion of fibre and axial parenchyma. For trees with larger stem diameter, the vessel diameter was also found to increase. In addition, the ray parenchyma and cell wall proportions in trees with larger stem diameter were lower than those in trees with smaller stem diameter. However, the wood properties obtained from the larger stem diameter trees did not always show lower values. The wood properties in N. cadamba were correlated to fibre wall thickness and vessel diameter.

Stem gravitropism and tension wood formation in Acacia mangium seedlings inclined at various angles

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.