In the present study, preliminary in vitro shoots propagation of Curcuma caesia Roxb. was investigated. Rhizome buds were used as explants and were cultured on Murashige and Skoog (MS) medium containing 6-Benzyl adenine (BA) alone or in combination with α-Naphthalene acetic acid (NAA). The results showed that the optimum shoot proliferation was obtained from MS medium containing 3.0 µM BA + 0.5 µM NAA. In this growth regulator combination, maximum 99.97 % explants produced 10.38 shoots with 4.53 cm length after 8 weeks of culture. Although spontaneous rooting was observed after 4 weeks of cultivation with all treatments using half strength MS medium containing IBA and NAA at different concentrations, high frequency of rooting (89.76 %) was obtained in 3.0 µM IBA (Indole-3-butyric acid) containing medium. The plantlets, thus developed, were hardened and successfully established in natural soil.

An efficient in vitro plant regeneration was achieved from hypocotyl-derived callus of a medicinal tree Phellodendron amurense. The expected morphogenic response was obtained on the media containing 0.89 mM 6-benzyl aminopurine (BAP) plus 4.52 mM 2.4-dichlorophenoxyacetic acid (2,4-D), 4.44 mM BAP plus 5.37 mM a-naphthaleneacetic acid (NAA), or 2.22 mM BAP plus 4.92 mM indole-3-butyric acid (IBA). A detailed histological study was undertaken to gain a better understanding of cellular changes that take place during the plant regeneration process from callus tissue. This study led to the identification of the cellular origin of shoot regeneration. Histological studies revealed that the new vegetative buds originated from callus that completely altered the morphology of the callus tissues by the 60th day of culture. It also revealed that BAP with NAA or IBA induces plant regeneration through organogenesis whereas BAP with 2,4-D induces embryo-like-structure (ELS) through hypocotylderived callus. The presence of ELS lacking root poles was also observed.

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Host-pathogen interactions were investigated on a Japanese birch (Betula platyphylla var. japonica, Tohoku) plantlet after infection with a canker-rot fungus, the Inonotus obliquus IO-U1 strain. For a time-course study, intact, wounded, and infected plantlets were collected from 2 h to 30 days after treatment. Notable changes were observed morphologically in the treated portion of wounded and infected plantlets. Phenolics first deposited at the cut margin and subsequently in vessels after 4 h of infection. Their deposition extended to other xylem elements, the cortex, and the pith with an increase in the infection period. Phenolics deposition was extensive at 10 days post-inoculation (dpi), when most of the cells were entirely filled with phenolics. A necrophylactic periderm (NP) was formed at the junction of the original periderm with a layer of 2-4 new phellem cells at 30 dpi. Based on the results obtained, phenolics deposition and NP formation are considered to occur as infection-induced responses in Tohoku birch plantlets infected with I. obliquus IO-U1.