Studies in the Regeneration of Horseradish: II. Correlation Phenomena

Regeneration has been studied in fragments of various sizes,and complete plants, together with the effect of externally-appliedß-indolylacetic acid (I.A.A.). The main conclusionsare as follows: (1) In the intact plant regeneration is inhibited by the growingcrown; in cuttings, I.A.A. will reduce the rate of primordium-formation,but cannot entirely suppress it. (2) The bud/root ratio among differentiated primordia is about0·5–0·9 in long cuttings; it rises sharplyin cuttings less than 2 cm. long, and falls in the presenceof I.A.A. Most, though probably not all, of the observationsconcerning this ratio can be explained on a simple auxin-levelhypothesis. (3) I.A.A., at an appropriate concentration, depresses the extensionof buds and promotes that of roots. On each cutting, only one(proximal) bud will normally extend—but this form of dominancecannot be exactly simulated by I.A.A., and more than one hormoneseems to be involved. The results are discussed from the point of view of hormonetheories of regeneration, and it is concluded that direct measurementsof internal auxin-content will be essential before the phenomenacan be interpreted with consistency.     

Somatic Embryogenesis in Cassava: The Anatomy and Morphology of the Regeneration Process

Anatomical and morphological studies demonstrated that somaticembryos developed similarly on mature seed and clonal leaf explantsof cassava (Manihot esculenta Crantz) cultured for 20–24d on Murashige and Skoog (MS2) basal medium supplemented with4.0 mg l^–1 2,4-D (Stage 1) before transfer to MS2 basalmedium supplemented with 0–01 mg l^–1 2,4-D and 0–1mg l^–1 6-benzylaminopurine (Stage II medium). Within 7d of inoculation onto Stage I medium, cell divisions occurredin the adaxial tissues of cotyledon-piece and leaf-lobe explants,and associated with this was the development of embryogeneticprotusions and ridges on the adaxial surface. Foliose structuresand somatic embryo initials developed from these tissues oncotyledon, embryonic axis and leaf-lobe explants and, when cultureswere transferred to Stage II medium, further somatic embryodevelopment occurred. Somatic embryos apparently originatedfrom groups of cells and were identified by the presence ofa closed root axis, a shoot axis and cotyledons of similar shapeand venation to those of zygotic embryos. Somatic embryos hadno vascular connection with parental cultures. Manihot esculenta, cassava, somatic embryogenesis, tissue culture, anatomy, morphology, morphogenesis     

Studies in the Renegation of Horseradish: III. External Factors

Initiation of new primordia on a freshly-cut root is relativelyinsensitive to external conditions, and may take place underconditions that inhibit the later stages. The latter show amarked temperature optimum for both regeneration and respirationat 30° C. Moisture is essential, but complete immersionin water is inhibitory; oxygen is essential, and excess (6 percent.) CO₂ without effect.     

獐牙菜属植物花蜜腺形态及解剖学

在扫描电镜下观察了獐牙菜属Swertia L.10组30种植物花蜜腺的数目,位置,形态和附属物等特征;同时还利用光镜对各组代表种的蜜腺结构进行了解剖学观察。结果表明獐牙菜属花蜜腺外部形态多种多,但在组与组之间无明显间断,演化序列呈梯度变化;内部结构基本相同,为不具维管束的结构蜜腺,且均为淀粉型蜜腺。因此,从花蜜腺的角度不支持将獐牙菜属划分为小属的观点,同时,还结合其它证据讨论了花蜜腺特征的演化趋势。     

Biophysical Studies on Rhinovirus and Poliovirus: I. Morphology of Viral Ribonucleoprotein

An explanation has been sought for the high buoyant density of rhinoviruses, which are classified as acid-sensitive picornaviruses. Heat degradation of purified preparations of rhinovirus type 1B and poliovirus type LSc leads to the extrusion of ribonucleoprotein strands. Contour lengths of these strands were measured by electron microscopy, and the molecular weights of rhinovirus and poliovirus ribonucleic acid (RNA) were determined. Values of 2 x 10(6) and 4 x 10(6) daltons were obtained for the molecular weight of poliovirus and rhinovirus RNA, respectively. This additional nucleic acid in the rhinovirion probably accounts for the increased density and may be related to the acid sensitivity of the rhinovirus.     

罗布麻的形态解剖研究--兼论中花罗布麻的分类问题

详细描述了3种罗布麻的形态解剖特征,指出它们的主要区别。对中花罗布麻的分类地位作了讨论,可将它作为罗布白麻的一个变型或变种,归纳入罗布白麻(Apocynum hendersonii Hook.f.)之中,暂可称为:中花罗布麻(Apocynum hendersonii Hook.f.var.salsuginodum Rus.)。但不应将它作为Apocynum pictum Schrenk或Poacynum pictum(Schrenk)Baill.看待。     

Photorespiration and Glycolate Metabolism: A Re-examination and Correlation of Some Previous Studies

Some previous studies of photorespiration and glycolate oxidation were re-examined and correlated by infra-red CO₂ analysis. Data about rate of photosynthesis and oxygen sensitivity indicated that complete inhibition of photosynthesis with 3-(3,4-dichlorophenyl)-1,1 dimethyl urea (DCMU) allowed dark respiration to continue in the light. Photorespiration was also inhibited. The oxygen sensitivity of glycolate-stimulated CO₂ production was found to be compatible with the proposal that glycolate is a substrate of photorespiration. Both `in vivo' and `in vitro' studies of the alga Nitella flexilis have revealed a pathway of glycolate oxidation similar to that of higher plants. DCMU inhibition of photosynthesis by Nitella gave results similar to those for the monocotyledons tested. Under very low light intensity, carbon dioxide compensation in corn was measurable but was not sensitive to high oxygen concentration. It appears that the lack of photorespiration in this plant is not the end result of efficient internal recycling of CO₂ to photosynthesis.     

Morphology and Anatomy of the Fern Genus Gymnogrammitis

The anatomy and morphology of Gymnogrammitis Griffith, the genericaffinity of which has been in dispute, is described in detailfor the first time. The diagnostic features are that the stemis protected by peltate scales with both marginal and superficialhairs. Its ground tissue is parenchymatous and is provided withnumerous pits on the cell-walls. Scattered among the parenchymaare a large number of groups of tanniniferous cells. The vascularcylinder is dorsiventral and is dissected into many small subequalmeristeles. The articulation pad, separating the petiole fromthe rhizome is homogeneous and is composed of thin-walled parenchymatouscells. Two large adaxial and two or more smaller abaxial bundlessupply the petiole. The receptacles are seated on the vein andare without any indusia. Spores are bilateral and have no perine;the ektexine is thick and bears many clava- or bacula-like projections.It is argued that the genus is a well-defined taxon and thatit shows affinities with the Davallioid ferns.     

Studies in the Genus Elaphoglossum: III. Anatomy of the Rhizome and Frond

The investigation is continued of a number of species of Elaphoglossumfrom Jamaica. Features of interest in the anatomy of the rhizome and frondare described. Information, additional to that previously recorded,is given of the scales. It is shown that, in E. villosum, complexityof stelar structure and the presence of hydathodea in the frondsis accompanied by scales of a specialized type.     

A Tropical Freshwater Wetland: I. Structure,Growth, and Regeneration

Forested wetlands dominated by Terminalia carolinensis are endemic to Micronesia but common only on the island of Kosrae, Federated States of Micronesia. On Kosrae, these forests occur on Nansepsep, Inkosr, and Sonahnpil soil types, which differ in degree of flooding and soil saturation. We compared forest structure, growth, nutrition, and regeneration on two sites each on Nansepsep and Inkosr soils and one site on the much less common Sonahnpil soil type. Terminalia tree sizes were similar on all three soil types, but forests differed in total basal area, species of smaller trees, and total plant species diversity. Terminalia regeneration was found only on the Inkosr soil type, which had the highest water table levels. Other Terminalia species are relatively light demanding, and T. carolinensis exhibited similar characteristics. It is therefore likely that Terminalia requires periodic, but perhaps naturally rare, stand-replacing disturbances (e.g., typhoons) in order to maintain its dominance, except on the wettest sites, where competition from other species is reduced. Terminalia swamps in the Nansepsep soil type appeared to be at the greatest risk of conversion to other uses, but swamps on all three types may face greater pressure as Kosrae's population increases and the island's infrastructure becomes more developed.     

A Comparison of the Morphology and Anatomy of Seedling Leaves of Lolium multiflorum Lam. and L. perenne L.

A rapid technique has been developed for studying the morphologyand anatomy of leaves of forage grasses. It has been used tocompare the leaf dimensions, numbers of structural elements,tissue proportions, stomatal and unicellular hair counts, andmesophyll cell number and size in one variety of Lolium multiflorumLam. and L. perenne L. There were large differences betweenthese species in leaf dimensions, number of structural elements,and in stomatal and unicellular hair counts, but little differencein the relative proportion of different tissues and in cellsize.     

Phytochrome: A Re-examination of the Quaternary Structure

Highly purified phytochrome samples from rye (Secale Cereale cv. Cougar) were fractionated by ultracentrifugation in isokinetic sucrose density gradients. Three protein species were separated with estimated sedimentation coefficients of 6.5S, 8.0S, and 11.5S. The 6.5S and 8.0S forms contained photoreversible phytochrome and produced a single subunit of 120,000 molecular weight upon reduction and electrophoresis in the presence of sodium dodecyl sulfate. The 11.5S species contained no detectable phytochrome. Reduction and electrophoresis of the 11.5S species in the presence of sodium dodecyl sulfate produced a major polypeptide of 32,000 molecular weight and a minor polypeptide of 48,000 molecular weight. The square tetrameric structures, observed by electron microscopy and previously thought to be phytochrome molecules, were found to be due to the presence of this 11.5S species in phytochrome preparations.     

Horseradish peroxidase—catalyzed hydroxylation of phenol: I. Thermodynamic analysis

We analyzed the horseradish peroxidase (HRP)—catalyzed hydroxylation of phenol in the presence of dihydroxy-fumaric acid and oxygen. All of the intermediate forms of the enzyme are reviewed. The last step of hydroxylation, consisting of the production of OH^• radicals that further react on phenol, is emphasized. Possible OH^• radicals production reactions were compiled and analyzed with respect to the available thermodynamic data. Some results of electrochemical experiments were also used to choose the correct set of reactions. At the end of analysis only two reactions for producing OH^• seemed to be consistent with the thermodynamic and experimental data. Neither of these reactions involved compound III or any other intermediate form of HRP. The last step of hydroxylation was thus totally independent of the pure catalytic cycle of the enzyme. As a consequence, HRP cannot be used as an hydroxylation enzyme in place of the P₄₅₀ cytochrome, as is sometimes suggested.     

HUMAN WOUND REPAIR : I. Epidermal Regeneration

A series of linearly incised superficial skin wounds was made on the forearms of young adult male volunteers. Wounds were sampled at several intervals between 3 hr and 21 days after wounding, for study by light and electron microscopy. The light microscopic observations show that regeneration of epidermis in human wounds conforms chronologically to that reported for the epidermis in superficial wound repair in laboratory animals. It is further shown that "ruffling" of cell membranes characterizes the cells of the migrating epidermis in early wound healing. This study reveals that the basement lamina and hemidesmosomes are established by epidermis in contact with the fibrin net at the base of early wounds. Epidermal cells in the wound environment are shown to be phagocytic. Analysis of the submicroscopic cytology of differentiating and maturing regenerated epidermis reveals that, in the sequence of events, the formation of filaments, basal lamina, and desmosomes is followed chronologically by evolution of keratohyalin granules and, subsequently, by keratinization of the surface epidermal elements. The entire sequence of migration, differentiation, and ultimate keratinization in the superficial wounds studied requires 3–5 days for completion.     

Studies in the Lauraceae: V. Comparative Morphology of The Flower

The morphological nature of the various parts of the lauraceousflower has been discussed on the basis of available evidencefrom floral anatomy and ontogeny. Evidence from floral anatomysupports the view that both whorls of perianth are homologousand that the inner whorl does not represent modified stamens.The perianth has not attained a level of differentiation intosepals and petals in a real sense. The lauraceous flower mighthave had staminal appendages in all the four whorls in the ancestralcondition. The living genera represent varying degrees of reduction.These appendages are regarded as modified stamens. The stamensin the family cannot be considered as reduced branch systems.The androecium is interpreted as consisting of stamen fascicles.The two-trace carpel is common in the family. Evidence fromontogeny and vascular anatomy makes it improbable that the gynoeciumconsists of more than one carpel. The carpel is essentiallyof the conduplicate type.