Magnolia sieboldii subsp. japonica (Oyama renge) is a deciduous tree that is native to Japan. This tree has value as a rarity because it is designated as an endangered species in some prefectures and, therefore, its conservation and reproduction are very important. We initially cultured immature seeds on Lepoivre medium (LP), half of nitrogen source of Murashige and Skoog medium (1/2N MS) and Woody Plant Medium (WPM) containing α-naphthaleneacetic acid (NAA) as an auxin and 6-benzylaminopurine (BAP) as a cytokinin. Proembryogenic masses (PEMs) were induced directly from immature seeds and somatic embryos were induced from PEMs. Immature seeds one to three weeks after flowering might be suitable to induce PEMs. Some somatic embryos formed roots and hypocotyls under condition of lighting. Finally, we transferred the somatic embryo-derived plantlets to soil in pots and the plantlets continued to grow. Thus, we developed a tissue culture system for plant regeneration for the propagation of M. sieboldii subsp. japonica.

The objective of this study is to investigate the changes in shear strength when cross-laminated timber (CLT) containing Japanese larch (Larix kaempferi) or Sakhalin fir (Abies sachalinensis) is used in a low humidity environment. We applied the over-drying treatments assuming a low humidity environment and boiling treatment (according to Notification 1446 of The Ministry of Construction of Japan) for comparison on CLT and performed out-of-plane and in-plane shear tests. Specimens for the out-of-plane shear tests were prepared from 5-layer 5-ply CLT, whereas specimens for the in-plane shear tests were prepared from 3-layer 3-ply CLT. Results from these tests suggested that: (1) Out-of-plane shear strength did not reduce by the over-drying treatment. However, it reduced approximately by 10% when subjected to boiling treatment; (2) In-plane shear strength reduced by 20 – 30% and 20 – 40% when subjected to over-drying treatment and boiling treatment, respectively; (3) The relationship between defects observed in external appearance and reduction in shear strength was not observed.

Buckling tests of flat cardboard were conducted using samples of various lengths under the hinged ends, and the critical condition for buckling of flat cardboard was examined. During the test, the relation between the load (P) and loading-line displacement (x) was measured. From the P-x relation, the deflection at the mid-length (δ) and flexural Young's modulus (E_B) were obtained based on elastica theory. The critical load for buckling was estimated from the following five methods: (A) load at the plateau in the P-x relation, (B) onset of nonlinearity in the P-x relation, (C) Southwell's method, (D) minimum value of the δ/P, and (E) Euler's equation. The buckling tests could be performed effectively by the simple apparatus used in this experiment. Additionally, Method D was optimal because the point transiting from compression to flexure could be determined more simply and objectively than the other methods.

In this study, we investigated the antitermitic activity of extracts from Cunninghamia lanceolata trunk and branch heartwood planted in Japan using Reticulitermes speratus. Strong antitermitic activity was observed in the n-hexane extract of C. lanceolata. From GC-MS (Gas chromatography-mass spectrometry) and GC-FID (Gas chromatography-flame ionization detection) analysis, cedrol and isoabienol were detected as the major components of the n-hexane extract of trunk and branch heartwood, respectively. Assays using both isolated components distinctly showed that cedrol exerted antifeedant activity at low concentrations and termiticidal activity at high concentrations, whereas isoabienol exerted only antifeedant activity, even at high concentrations. These results suggested that cedrol and isoabienol in the heartwood of the trunk and branch of C. lanceolata were strongly involved in antitermitic activity against the Japanese termite, R. speratus. Furthermore, the intensity of termiticidal and antifeedant activities exerted by cedrol and isoabienol depended on the concentration of each component in the heartwood.

Three shear tests conducted on three-layer cross-laminated timber (CLT) of Japanese larch, and the effects of defects and edge-gluing of transverse layer laminae on shear strength were investigated. The shear strength obtained from three-point bending test was approximately the same as that obtained from asymmetric four-point bending test. The shear strength obtained from compression type tests was lower than that obtained from three-point bending tests, and the difference between those was significant at 5% level. The defects and edge-gluing of transverse layer laminae had no effect on the shear strength of CLT. The effects of failure process of transverse layer laminae on maximum shear load of CLT were investigated by Monte-Carlo simulation. The CLT reached the maximum shear load after some of laminae in transverse layer was failed.