This review deals with production of condensed tannins and four types of hydrolysable tannins by plants tissue cultures, especially of woody plants. Tannins are plant polyphenols which are widely distributed in the plant kingdom. Medicinal plants that contain high amounts of tannins have been used in traditional medicine, and various pharmacological activities of tannins, such as anti-virus and anti-tumor effects, have been newly discovered. The effective production of such bioactive tannins in plant cell cultures has been required for further studies of their biological activities or for development of new natural medicines. Several cell and tissue cultures which are capable of producing a large amount of condensed and hydrolysable tannins have been established from tannin-producing plants. Galloylglucoses were common constituents in those undifferentiated cell cultures induced from plants producing hydrolysable tannins. Ellagitannin production was accompanied by tissue differentiation of these cell cultures, substantiating that galloylglucoses were precursors of ellagitannins. Tannin production was controlled by culture conditions, especially the concentration and the ratio of nitrogen sources in the culture media as well as light irradiation.

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Wood properties and their variation in the stem of 17-year-old Melia azedarach trees, which grew fast and had straight stem forms due to pruning, were investigated to clarify the potential of this species as a fast-growing tree in Japan. The test trees were grown as seedlings from the same mother tree. The diameter at breast height ranged from 21.4 to 32.7 cm. Growth ring width near the pith up to 3 m height above ground was large and became stable beyond the 4th ring regardless of stem height.
The specific gravity when air-dry increased slightly from the pith outward and with increasing stem height. The pattern of distribution of specific gravity showed that there were low and high specific gravity zones in the stem. The compression strength in the stem varied in a trend similar to that of specific gravity. There was a significant correlation between specific gravity and compression strength at the 1% level. Stems up to 4 m height above ground have been used because of the umbrella-type crown form, but correction of stem form by pruning has made it possible to use stems up to 8 m in height.

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To study mechanical properties of wood exposed to variations of temperature, in this study the swollen wood (water-swollen wood & ethylene glycol-swollen wood) was preheated at 30-180°C and quenched to 20°C or preheated at 90-180°C and quenched to 80°C. After the swollen wood had been quenched for 3 minutes, stress relaxation of the wood was measured in the radial direction for 3 hours.
Relaxation modulus (E_t), relative relaxation modulus (E_t/E₀), fluidity of quenched wood (1-E_t/E₀) and the relative fluidity of quenched wood to unquenched wood were calculated from the stress relaxation curves. The results obtained are as follows :
1) The swollen wood that was quenched from 30-180°C to 20°C showed four characteristics in the unstable state depending on the temperature range. The relative fluidity varied slightly at 30-40°C and increased sharply at 40-90°C. From 90°C to 140°C, the relative fluidity held a constant value. Above 140°C, the relative fluidity increased once more.
2) The maximum value of relative fluidity for quenched wood was 2.5-3.2 times the value of unquenched wood which was kept at 20°C.
3) An unstable state occurred as swollen wood was quenched from 90-180°C to 80°C. It shows that the unstable state would also occur over 80°C, which is the transition temperature of water-swollen wood as above.
4) After the swollen wood had been quenched from 80-180°C to 20°C, after 3-4 months the mechanical properties of swollen wood were almost the same as those of unquenched wood, but it needed a long time to reach the stable state.
5) The stress relaxation of swollen wood at 20-150°C was discussed and apparent activation energy was calculated. The value of apparent activation energy differed depending on temperature in the range of 20-150°C, which makes it possible to bring about the unstable state.

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To study the optimum experiment conditions for determining the mechanical properties of wood which is in an unstable state due to temperature changes, the fluidity (1-E_t/E₀) in stress relaxation, the modulus of elasticity (MOE) and the bending strength of wood were examined. The results obtained are as follows :
1) The fluidity (1-E_t/E_o) was independent of initial deformation in stress relaxation.
2) The stress relaxation process of water-swollen wood that was immersed in water at 80°C for 3 days was almost the same as that immersed for 0.5 days. Mechanical properties of wood are therefore not affected by hydrolysis or thermal decomposition if the temperature is below 80°C.
3) A change of stress relaxation was determined in 0.5∼3 min after the wood was rapidly exposed to high temperature. As a result, the best condition to evaluate the degree of instability of wood is 0.5∼3 minutes after a temperature change.
4) When wood was quenched and returned to the initial temperature quickly, the relative relaxation modulus did not change in comparison with control specimens that were in a stable state for a long time, because of the memory function of wood as a high molecular material.
5) The bending strength of wood decreased under the unstable state.

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To clarify the effect of electrical potentials on the tool-wear progression of high-speed steel tools in the machining of air-dried Douglas-fir (Pseudotsuga menziesii FRANCO), tool-life tests of planer knives or machine bits were conducted by applying electrical potential of -2, -1, 0, +1, or +2 kV to the tool. When applying -2 kV to the tool, tool wear for each tool progressed extremely slowly due to the suppressive effect of cathodic protection on corrosive wear. However, when applying +2 kV to the tool, tool wear for each tool progressed rapidly. In the machining of air-dried Douglas-fir, the effect of the electrical potentials was clearly seen, producing the same results as with wood of high moisture content. The effect was more remarkable with the machine bit than the planer knife. Furthermore, cutting tests with a sharp knife or a worn knife were carried out without applying any electrical potential. The voltage of the static electricity of the knife during cutting was measured, and the electrostatic effect as the cause of tool wear was discussed. During cutting, electrical discharges between tool and work piece occurred repeatedly. The measured voltage of static electricity was higher for the sharp knife than for the worn knife.

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Hibiscus cannabinus (kenaf) plants grown in the Agricultural and Forestry Research Center at the University of Tsukuba were separated into three parts, (upper, middle and lower), and their bast and core parts were subjected to protein, lignin and carbohydrates analyses. We clarified the differences of the chemical features of these parts. The lower part of the core contained more lignin and xylan than the upper part and the upper and lower bast parts. The core accumulated a large amount of lignin with a high syringyl to guaiacyl ratio, which suggests rich non-condensed lignin structures. Cooking efficiency of the bast was compared with that of Acacia mearnsii, Eucalyptus spp. and Cryptomeria japonica wood under kraft-anthraquinone pulping conditions. Although the lignin content of the bast was lower than that of A. mearnsii wood, the selectivity of delignification of the bast was not better than that of the hardwood in the kraft pulping process. However, the bast pulp was easily oxygen-bleached, resulting in a low kappa number.

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Aldehydes and volatile organic compounds (VOCs) emitted from commercial laminated veneer lumber (LVL) were determined using the JIS small chamber method for 21 days. LVL samples were made from three different veneer species, namely larch (Larix spp.), radiata pine (Pinus radiata D. Don) and sugi (Cryptomeria japonica D. Don), and were bonded with phenol-formaldehyde resins for structural use and melamine-urea-formaldehyde resins for non-structural use. Effects of veneer species, adhesive type, and formaldehyde scavenger on aldehyde and VOC emissions from LVL samples were investigated. The emission factors of aldehydes, VOCs and total VOC (TVOC) decreased during the 21 days in the small chamber with only a few exceptions. The highest emission factors of formaldehyde and acetaldehyde were determined in radiata pine LVL. Adding the formaldehyde scavenger to LVL samples decreased the formaldehyde emission factors by 50% or more. The variety and amount of VOC emissions were strongly dependent on the veneer species. It was therefore concluded that the predominant VOCs derived from the veneer. All the LVL samples used in this study had very low emissions of VOCs according to the indoor air quality guidelines of the Japanese Ministry of Labor, Health and Welfare.

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