ULTRASTRUCTURAL AND ENZYMATIC EVIDENCE FOR THE PRESENCE OF MICROBODIES IN THE FUNGUS ACHLYA

Ultrastructural evidence for structures resembling microbodies is presented for the fungus Achlya ambisexualis Raper. These structures are DAB positive and thus presumably contain the enzyme catalase. Activities from mycelial homogenates for. the following enzymes are given: catalase, glycolate oxidase, uricase, isocitrate lyase, malate dehydrogenase, citrate synthetase, malate synthetase and glutamate: oxaloacetate transaminase. These results suggest that Achlya contains microbodies and that they may be of the glyoxysome type. The specific activity of catalase increases substantially following initiation of antheridial hyphae by the hormone antheridiol.     

FURTHER EVIDENCE FOR THE PRESENCE OF A PANETH CELL PROGENITOR IN MOUSE INTESTINE

Photomicrographic evidence, mitotic figures and ³H-thymidine labeling among Paneth cells, is presented in support of the hypothesis that Paneth cells are replaced by cells proliferating in the bottom of the intestinal crypt rather than by migration of cells from the mid-crypt region.     

THE TRANSITION FROM FILAMENTOUS TO TWO-DIMENSIONAL GROWTH IN FERN GAMETOPHYTES. I. THE REQUIREMENT FOR PROTEIN SYNTHESIS IN GAMETOPHYTES OF PTERIDIUM AQUILINUM

Two-dimensional (2-D) development of gametophytes of Pteridium aquilinum was estimated by the percentage of plants with at least one cell wall at an oblique angle, relative to the long axis. Inhibition of cell division per se was assayed by counting the cell number per filamentous (1-D) gametophyte. Specific concentrations of 8-azaguanine, 5-fluorouracil, p-fluorophenylalanine, actinomycin D, streptomycin, and cycloheximide were found to selectively inhibit 2-D development. A reduction in the percentage of 2-D gametophytes was accompanied by a reduction in the relative protein content (protein per dry weight). A comparable association was found only during the initial stages of 2-D development; after 5 days the relative protein content decreased as the percentage of 2-D gametophytes increased. Different intensities of white light resulted in a 10-fold difference in the percentage of 2-D plants with no alteration of the relative protein content. These results demonstrate that no strict relationship between 2-D development and relative protein content occurred in these gametophytes.     

INTERPOPULATIONAL VARIATION IN THE GAMETOPHYTES OF PELLAEA ANDROMEDAEFOLIA

The development and mature morphology of the gametophytes from both sexual and apogamous populations of the fern Pellaea andromedaefolia were investigated. While most sexual examples were indistinguishable, some differences were noted. An insular collection was distinctive in its variability and irregularity of form. Although the latter was a representative of var. pubescens, other collections of the variety could not be distinguished from var. andromedaefolia on the basis of gametophytic characteristics. The apogamous gametophytes were decidedly more variable in development and often very different from sexual thalli. The mature asexual thalli tended to be more irregular in form and usually sharply divergent from the typical cordate type characteristic of the sexual populations. Each of the five apogamous samples was unique with respect to gametophyte development. The differences among the gametophytes of the various populations do not correlate with the sporophytic characteristics which differentiate the two varieties of the species.     

THE CONTROL OF THE ORIENTATION OF CELL DIVISIONS IN FERN GAMETOPHYTES

Time-lapse observations of filamentous fern gametophytes were used to evaluate whether the plane of cell division is referable to the plane of minimal surface area before and during the transition to two-dimensional growth. Cell dimensions of the apical cell were related to the length/width ratios associated with minimal area in the transverse plane vs. longitudinal plane, by modeling the apical cell as a hemisphere subtended by a cylinder. Our working hypothesis predicts that filamentous growth is perpetuated by an apical cell geometry that makes the transverse division plane the orientation of minimal surface area, whereas the transition to two-dimensional growth (longitudinal division of the apical cell) occurs once the longitudinal plane becomes the position of minimal surface area. The predictions of this hypothesis are fulfilled regardless of variations in light intensity and light quality, the presence of regulators of metabolism, or whether the experimental perturbation causes a corresponding selective inhibition of the transition to two-dimensional growth. Thus, the control of the plane of cell division in this system seems to depend on thermodynamic considerations of surface area. Furthermore, we favor the conclusion that the role of the genome in the transition to two-dimensional growth involves its influence on apical cell dimensions rather than the induction of specific genes for specific morphogenetic mRNAs.     

EVIDENCE FOR VARIATION IN THE QUANTITY OF DNA AMONG PLASTIDS OF ACETABULARIA

The DNA content of individual plastids of the giant unicellular algae Acetabularia mediterranea, and Polyphysa cliftoni was studied. Four methods were used for localizing DNA: acridine orange staining, radioautography following actinomycin D-³H treatment, electron microscopy of thin tissue sections, and electron microscopy of osomotically disrupted plastids. With each method, DNA was readily detected in 20–35% of plastids, but no DNA was observed in the remaining 65–80%. The results further showed that in those plastids with detectable DNA the amount of DNA present was variable. The sensitivity and reliability of the localization methods are discussed, and the possible implications of these findings are considered.     

EVIDENCE FOR THE PARTICIPATION OF THE GOLGI APPARATUS IN THE INTRACELLULAR TRANSPORT OF NASCENT ALBUMIN IN THE LIVER CELL

A comparative biochemical and radioautographic in vivo study was performed to identify the site of synthesis and route of migration of albumin in the parenchymal liver cell after labeling with leucine-¹⁴C or leucine-³H via the portal vein. Free cytoplasmic ribosomes, membrane-bound ribosomes, rough- and smooth-surfaced microsomes, and Golgi membranes were isolated. The purity of the Golgi fraction was examined morphologically and biochemically. After administration of leucine-¹⁴C, labeled albumin was extracted, and the sequence of transport was followed from one fraction to the other. Approximately 2 min after the intravenous injection, bound ribosomes displayed a maximal rate of leucine-¹⁴C incorporation into albumin. 4 min later, a peak was reached for rough microsomes. Corresponding maximal activities for smooth microsomes were recorded at 15 min, and for the Golgi apparatus at ~20 min. The relative amount of albumin, calculated on a membrane protein basis, was higher in the Golgi fraction than in the microsomes. By radioautography the silver grains were preferentially localized over the rough-surfaced endoplasmic reticulum at the 5 min interval. Apparent activity in the Golgi zone was noted 9 min after the injection; at 15 and 20 min, the majority of the grains were found in this location. Many of the grains associated with the Golgi apparatus were located over Golgi vacuoles containing 300–800 A electron-opaque bodies. It is concluded that albumin is synthesized on bound ribosomes, subsequently is transferred to the cavities of rough-surfaced endoplasmic reticulum, and then undergoes migration to the smooth-surfaced endoplasmic reticulum and the Golgi apparatus. In the latter organelle, albumin can be expected to be segregated together with very low density lipoprotein in vacuoles known to move toward the sinusoidal portion of the cell and release their content to the blood.     

南岭东部新仙女木事件的孢粉学证据

冰消期至早全新世的仙女木事件（Ｙｏｕｎｇｅｒ Ｄｒｙａｓ,简称ＹＤ）,因降时间短,气候波动强,是全球气候研究者关注的热点。根据近期的研究,ＹＤ事件上在欧洲、北美和我国北方都有所表现。但在我国长江以南的内陆地区,未见报道。笔者在用孢粉资料探讨我国南方南岭东部地区１５０００ｙｒ ＢＰ以来的植被与环境演变时,发现约在１０４００ｙｒ ＢＰ前,植被发生了较大的变化,气候有一较明显的降温被动,这是我国低纬度人     

THE DISTRIBUTION AND TAXONOMIC SIGNIFICANCE OF LIGNIN IN THE LEMNACEAE

Lignification characteristics of 14 species of Lemnaceae were studied by the alkaline oxidation technique in an attempt to resolve conflicting reports of the presence of lignin and to provide chemotaxonomic data for supplementing previous systematic treatments. Four species of Spirodela, eight of Lemna, Wolffiella oblonga, and Wolffia microscopica were clonally subcultured, homogenized, exhaustively extracted and the insoluble residue oxidized in alkaline cupric hydroxide. Barley (Hordeum vulgare), Elodea densa and Spirogyra sp. were examined to validate the technique. The benzaldehydes were extracted, separated by thin-layer chromatography, and quantitated spectrophotometrically. Recovery of syringaldehyde, vanillin, and to a lesser extent p-hydroxybenzaldehyde, was accepted as evidence that these plants are lignified. The highest yields of syringaldehyde and vanillin were recovered from S. intermedia, the largest member of the Lemnaceae. Lesser amounts were obtained from S. polyrhiza and S. oligorhiza. Spirodela biperforata yielded no syringaldehyde which substantiates its distinctiveness from the morphologically similar S. polyrhiza. All Lemna species are nerved, yet vanillin (but not syringaldehyde) was recovered only from L. trinervis, L. perpusilla, L. minor, and L. minima. The species L. trisulca, L. gibba, L. obscura, and L. valdiviano yielded only p-hydroxybenzaldehyde. Thus the presence of nerves is not evidence for lignification within the genus Lemna, and the relationships suggested by their gross morphology are not supported by their lignin chemistry. Wolffiella is non-lignified by these criteria. Wolffia microscopica is the smallest flowernig plant and it has no nerves; vanillin was unexpectedly recovered and microscopic examination showed highly lignified anther walls.