Tobacco cultured cell clone XD-6S, which was subcultured on the medium containing 2, 4-D (2, 4-dichlorophenoxyacetic acid), was induced to form shoots when the cells were transplanted to medium containing IAA (indole-3-acetic acid) and kinetin instead of 2, 4-D. Medium containing 0.01ppm of IAA and 1ppm of kinetin is optimal for shoot formation. Fine structural changes in the cells were observed electron microscopically before and after shoot induction. Developing crystal containing bodies were first seen on the 7th day following transplantation to medium containing IAA (0.01ppm) and kinetin (1ppm). Although the bodies could be seen in cells cultivated on medium with IAA or with kinetin and even on medium containing no additional growth substances, the bodis were most frequently seen in cultures in which shoots had been induced, e. g. cells grown on medium with IAA (0.01ppm) and kinetin (1ppm). The body is an electron dense cell organelle which is about 1μ long in diameter and has a lattice spacing of 70-110Å. This body is similar to ones which were found by other investigators, but the lattice space is somewhat different.
An electron microscope study of the effect of benzimidazole and nicotinamide adenine dinucleotide on the senescence of Elodea chloroplasts is described. It was found that benzimidazole results in maintaining at least, or even in enhancing tendency of the lamellar structure of the chloroplast, whereas nicotinamide adenine dinucleotide remarkably accelerates the degeneration normally occurring during senescence. It is suggested that this result may account for the increased rate of photosynthesis found in benzimidazole treated leaves.