The variability in gross morphology of two species of Maianthemum, namely, M. Bifolium of Eurasia and M. canadense of central and eastern North America, is illustrated in this study with particular emphasis on the variations in quantitative characters. A comparison of the three species of Maianthemum, including an amphi-Pacific species, M. dilatatum (=M. kamtschaticum auct.) is also made, based upon all the available information, and their taxonomic status is discussed. Considering their close resemblance in gross morphology, their karyotypic and ecological similarities, these three species are evidently closely related, but they can at the same time be regarded as distinct species which exhibit almost complete allopatry and each of which has conspicuous diagnostic characters. Of the three species, however, M. dilatatum is the most variable one and consists of three discrete geographic population groups. It is to be considered that polyploidy has apparently not played a significant role in the speciation of the genus Maianthemum. Most clones cytologically investigated thus far by various authors have a diploid somatic chromosome number of 36, although occasional triploid (2n=54), tetraploid (2n=72), and other chromosome numbers (2n=64-70) have been reported in plants of the above three species. Such cytotypes are now considered to be of autopolyploid origin, which have arisen spontaneously within or at marginal areas of their distribution range.
In Cucumis sativus, a number of small prolamellar bodies were formed in the plastid, when the latter, containing grana lamellae, was transferred to the dark. These prolamellar bodies showed more rapid response to the change in light and temperature as regards their appearance and disappearance than in the case of fully etiolated plastids. At the higher temperature (26°), a lower intensity of light induced the formation of prolamellar bodies at an earlier stage of plastid development. At lower temperature (12°), however, no prolamellar body was formed throughout the entire course of plastid development, and the prolamellar bodies which had been formed in the dark rapidly disappeared at an early period after the seedlings were transferred from the dark to the light (400lux). Furthermore, the investigation on the effect of different wavelengths of light upon lamellar formation was made. From these results, it seems that the prolamellar bodies appear in the case where the rate of vesicle formation exceeds the rate of conversion of vesicles into the lamellar system.
The discovery of a direct ancestor, Ipomoea trifida (6x), of the sweet potato (6x) in 1961-1962 has been followed by a further finding of its diploid (I, leucantha) and tetraploid (I. Littoralis) predecessors. On the basis of cytogenetical study it was reasonably assumed that I. Littoralis (4x), I. Trifida-(3x)-6x, I. Trifida (6x) and I. Batatas (6x), sweet potato, are autoploids derived rather from the doubling of a set of 15 chromosome pairs (genome B) of I. Leucantha (2x) than from segmental alloploidy. On the other hand an artificial hexaploid, I. Littocantha, synthesized from I. Leucantha (2x) and I. Littoralis (4x) was proved to have the same genome constitution as I. Trifida-(3x)-6x and sweet potato, their Fl hybrids having 45 bivalents or modified configurations. The hybrids were fertile. Another artificial hexaploid, I. lacunocilis, derived from I. lacunosa (2x) and I. gracilis (4x) was self-fertile, but usually did not hybridize either with I. trifida or sweet potato. The phylogenetic relationship was fairly well supported by the pattern of the mating system in interspecific crosses.
Cellulases in a crude bromelain preparation obtained from the juice of pineapple stem tissue were fractionated by column chromatography into at least four components. Several enzymic properties of the main component, cellulase I, were examined and compared with those of the fungal cellulases. It was found that most of the enzymic properties of cellulase I are quite similar to those found in some cellulase components of a fungus, Trichoderma virile.
Two types of spontaneous polyploidy were found in the interspecific hybrids. One of those is the binucleate cells (24II+2BI at MI) which were observed with a frequency between 3 and 8 per cent in PMCs of Lilium×'Tsukiha' (2n=24+ IB, I2+ IB1), an artificial hybrid of L. maximowiczii 'Akatsuki'×L. purnilum 'Golden Gleam'. The other is a multiple allotriploid hybrid L. x 'Fire King' (2n=36, 12III), one of Stooke's Hybrids. The increase in ploidy in the latter may have arisen spontaneously from fertilization between a normal haploid gamete and an unreduced one during the breeding program. The karyotypes of these two hybrids are heterozygous with respect to various secondary constrictions. The extent of chromosome pairing, however, indicates the close genomic relationships of the parental species.
In nine clones of Rumex acetosa L., a study was made on morphological variation of certain autosomes which are distinguishable from the others by a smallness of long arm. They range in arm ratio from 0.15±0.01 to 0.96±0.01 and show no difference in length of long arm, with a few exceptions. The autosome with arm ratio of 0.61± 0.02 or more bears a heterochromatic segment in the distal part of one arm, while the remaining autosomes bear no heterochromatic segment. The decrease in arm ratio among all the autosomes studied is considered to be due to having lost, little by little, the heterochromatic segment, and further to having similarly lost the just inner segment. This segment appears as a hyaline band or a thin scarcely-stained thread at mid-prophase and seems to be slightly different in character from an euchromatic segment.
In segments of etiolated Avena coleoptiles, the dark process of Pfr decay was prevented by several metal-complexing and sulfhydryl compounds, and this inhibition was partly recovered when such metallic ions as ferrous, ferric or zinc ion were given to the tissues. Ferric ion recovered the EDTA- and a, a'-dipyridyl-induced inhibition, but had less effect on the 2-mercaptoethanol-induced one. In contrast, zinc ion recovered the latter as well as the former. The inhibition of dark Pfr decay also occurred in the presence of respiratory inhibitors such as azide, antimycin A and rotenone. The azide-induced inhibition was not recovered by the addition of ferric or zinc ions. Thus, the dark Pfr decay appeared to be controlled at, at least, three different processes in this tissue.