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.
The sporocarp formation in Salvinia natans was greatly accelerated in the first short day cycle consisting of 8 hour light and 16 hour dark periods, when 90% CO was given during the photoperiodic dark period. As the number of photoperiodic cycles increased, the number of sporocarps always became greater than that of controls. The sporocarp formation under CO application was accelerated in the dark period longer than 12hours. In 8hour dark period, the sporocarps were initiated only when CO was applied, and it was suggested that CO can shorten the critical dark length of the plants. The most effective time for the acceleration of sporocarp formation by CO in 16hour dark period was found in the fourth quarter of the dark period, i. e. from 12 to 16hours after the beginning of the dark period, and somewhat effective in the third quarter, whereas the CO applied during the first or the second quarter of the dark period was ineffective. The result seems to be consistent with the fact that the effect of CO to accelerate the sporocarp formation was observed only in the dark period longer than 1 2 hours. No sporocarp was formed with the preceding photoperiodic cycle alone, consisting of the light and the light-interrupted dark periods. But, the sporocarps were initiated when the preceding cycle was followed by the cycle of main dark period. Thus, the number of the sporocarps was increased in the following order; (1) the non-CO treated dark period which was light-interrupted in aerobic condition, (2) the CO-treated dark period which was light-interrupted in aerobic one, and (3) the anaerobic dark period light-interrupted in anaerobic one. From these results, it is suggested that a metabolic system which produces a photoperiodic stimulus is originally formed with the photoperiodic treatment and that an O2-independent process is contained in the later stage of the dark reaction in the metabolic system. The promoting effect of CO on the sporocarp formationmay be due to the activation of the O2-independent process, and some O2-dependent processes may also be involved in the light interruption.
Karyological studies were made on three Japanese species of Asplenium: A. incisum, A. tripteropus and A. oligophlebium. The somatic chromosome numbers of these species were found to be 2n=72, of which A. oligophlebium was first determined. The chromosome number 2n=72 of our A. tripteropus was found to be a half of the number n=72 of which Mitui (1965)1)j proviously found. Essentially, the chromosome complements of these three species can be divided from the morphological view point into six (A-F) types and furthermore, each type can be divided into two groups. From these observations, the primary basic number of Asplenium can be considered to be b=12. Therefore, the species in the genus Asplenium, which possess chromosomes 2n=72, can be considered to be a hexaploid.