Library

Notes: Summary 1. Reciprocal crosses were carried out between representatives of the group of Eu-Oenothera on the one hand and those of groups Raimanniaor Renneria-Oenothera, resp., on the other, in order to homologize the numeration of their chromosome ends. The crossings were often unsuccessful, especially when the Eu-Oenothera were functioning as female plants. It appears that the constitution of the plastome is frequently responsible for the death of the hybrids. 2. The diakinesis configurations of the chromosomes typical for each hybrid were determined as far as this was possible. The investigations were rendered extremely difficult by the high rate of missing connections in the chromosome rings and chains. The typical configurations could only rarely be observed but rather had to be derived from comparisons of torn chromosomal chains. The typical configurations as determined consist mostly of many-membered rings. 12°+2°, 10°+2°+2°, 10°+4° and 14° are by far the most frequent. 3. In some types of the hybrids other configurations occurred in addition to the characteristic configuration, which, however, could not be reconciled with their characteristic one. In most instances certain deviating chromosomal configurations were preferably observed. Even trivalent connections occurred in these forms, which are not expected in the normal Oenotherae with 14 chromosomes. 4. Point (2) and (3) are obviously the result of the distant genetic relationship between the partners of the crossing. This reduces the formation of chiasmata because of a lower intensity of pairing, which again leads to an increased failure to end connections. Furthermore, the pairing of non-homologous chromosomes is increased (trivalent connections!) which may lead to translocations resulting in deviations from the typical configuration. These frequently occurring deviations in configuration make it probable that short homologous segments do exist in the pairing chromosomes which are strictly speaking non-homologous. The rate of translocations in Oenothera is apparently determined to a large extent by endogenous genetic factors. This assumption is supported by other findings.

Notes: Summary A typical cell of a (+)-gamete ofChlamydomonas reinhardii was reconstructed on a uniform scale at a magnification of X36,000 by means of serial-section electron microscopy. The absolute and relative volume of 2 cells and of their organelles was determined by quantitative measurements. -The chloroplast occupies about 40% of the volume of the cell. Its basic form is unsymmetrically trough-shaped, but may vary very much by the occurrence of smaller or larger lobes at its rims. In that way also cup-shaped types are formed. -The nucleus occupies about 10% of the volume of the cell. The nuclear envelope contains about 6 pores perμm2, the diameter of the latter measuring about 100 nm. Cisternae of the ER far ramifying into the cytoplasm are in communication with the outer membrane of the nucleus. -The cells frequently contain only 2 dictyosomes which are arranged near the nucleus. The area close to the Golgi-cisternae occupies about 1% of the volume of the cell. One of the cisternae of the ER branching from the nuclear envelope is nearly always inflated like a vacuole, and forms near the dictyosomes a wide, velum-like envelope. It produces many vesicles which probably contribute to the regeneration of the Golgi-cisternae. Also the dictyosomes detach vesicles, which partly may be used for the formation of the contractile vacuoles. -The mitochondria occupy about 3% of the volume of the cell. Their number per cell is only about 10–15. They are frequently very elongated, often sinuous, articulated by constrictions, and branched. Most of them are located very close to the surface of the chloroplast; a special group is situated near the basis of the flagellae. Characteristic associations often occur between mitochondria and other organelles (chloroplast, vacuoles, lipid bodies) sometimes possibly including close contact of the enveloping membranes. Close associations also occur between some special ER-cisternae and the chloroplast. -The vacuoles occupy 8% of the volume of the cell. It is possible to distinguish 4 types of them in a cell: (a) Simple static vacuoles containing a single interior space. (b) Composed static vacuoles containing several separate interior spaces. (c) Contractile vacuoles, which after their emptying are reformed by the fusion of small vesicles. (d) A vacuole-like inflated cisterna of the ER, located near the dictyosomes, which always communicates with the nuclear envelope, and sometimes also with static vacuoles. Only the type (c) of the vacuoles shows, in certain cases, an irregular shape of its outline, while the transition of vacuoles into small ER-like cisternae is only to be seen at the type (d). About 5 lipid bodies occupy about 0.5% of the volume of the cell. They show communications with the ER. The possibility is discussed, whether the cytomembranes and the organelles surrounded by membranes form, at least temporarily, a continuous system in the cell.

Notes: Zusammenfassung 1. DieTypen A, B undC sind monomorph-trisome Mutanten derOenothera odorata, von denen man erwarten müßte, daß sie nur den normalen 7 chromosomigen Komplexv im Pollen übertragen. 2. Während dies beiTyp C tatsächlich zutrifft, kommt es beiTyp A und besonders beiTyp B auch zur Vererbung des 8chromosomigen KomplexesI B , wenn auch immer in geringer Häufigkeit. 3. Bis zur Reife der Antheren entwickeln sich dieI A -,I B - undI C -Pollenkörner der genannten Mutanten morphologisch völlig normal. 4. Die Pollenkörner mit den KomplexenI A undI C und der größte Teil derI B -Körner sind nicht in der Lage, Pollenschläuche auszubilden. 5. Die Pollenschläuche der keimfähigenI B -Pollenkörner erreichen die Samenanlagen offenbar ohne weitere Hemmung ihres Wachstums.

Notes: Summary 1. In the progeny of radiation-induced diploid X1-variants of)enothera bertetiana, trisomic mutants were found quite frequently. The object of the described investigations was to elucidate the cause of this phenomenon. 2. In these X1-variants, deviating diakinesis configurations attributable to radiation-induced translocations were observed frequently. For example, instead of the normal 14-chromosome ring, 2 rings were often found, both rings being even-numbered or both odd-numbered. 3. The X1-mutants with odd-numbered diakinesis rings are chiefly responsible for the segregation of trisomic plants in the X2. For in this instance, as a consequence of quite normal chromosome distribution in the anaphase, a quarter of all gones receive n+1 chromosomes. After combination with normal n-pollen, 2n+1 plants are obtained. Thus in this case trisomic plants are formed without usual spontaneous non-disjunction. 4. To a lesser degree, plants with deviating chromosome numbers were also found in the progeny of X1-mutants which had even-numbered diakinesis rings. The occurence of such plants is attributable to non-disjunction, which is evidently furthered by radiation-damaged chromosomes.

Notes: Summary 1. Among the progeny of diploid X-ray mutants ofOenothera berteriana trisomic plants appear in a higher frequency than usual. The cause of this phenomenon has been clarified already in former researches (Arnold undKressel, 1965). Cytological observations of these trisomic mutants demonstrated that in diakinesis there are very often arrangements of chromosomes which led to the conclusion that translocations had taken place. It was the aim of this work to show the cause of this phenomenon. 2. We were able to point out that part of the translocations was caused by the original X-ray treatment. As well, however, it could be demonstrated that many translocations use to occur only in the trisomic plants. So a translocation in the trisomic plantM:K led over to the existence of the mutantM:Kb. This means that in many cases the trisomic constitution is followed by an increase of the rate of translocation. 3. This is supposed to be induced by abnormal pairing caused by a supernumary chromosome. Pairing of non-homologous chromosomes occur. An exchange of segments after a pairing of non-homologous chromosomes however, leads to a reciprocal translocation. 4. In some trisomic types it has been shown that only certain chromosomes participate in the translocation. From this we conclude that we do not have a pairing of real non-homologous chromosomes, but that there are short homologous segments on the two non-homologous chromosomes.

Notes: Abstract The proteins from cytoplasmic ribosomal subunits of eight species of algae were analyzed by two-dimensional gel electrophoresis. The molecular weights of the proteins were in the range of 10,000 to 55,000. We have compared the protein patterns from the ribosomal subunits of the different species to those of Chlamydomonas reinhardii. It was quite clear that there are many similarities in the protein patterns of all the investigated species. We found for Chlamydomonas eugametos 48, Chlamydomonas noctigama 42, Chlorogonium elongatum 47, Scenedesmus obliquus 40, Chlorella fusca 35, and Euglena gracilis 35 proteins which were homologous to those of Chlamydomonas reinhardii. For the colorless flagellate Polytoma papillatum, we detected 45 proteins homologous to Chlamydomonas reinhardii, so that the generally assumed close relationship between Chlamydomonas and Polytoma is confirmed.

Notes: Abstract Several details have been published cocerning the mitochondrial number and shapes at various stages of the synchronized vegetative and generative cell cycle in Chlamydomonas reinhardii. The present study, based on ultrathin serial sections and threedimensional reconstructions, completes these data. Quantitative analysis of serial micrographs makes it possible to give specific details of mitochondrial volumes in cells at early intermediate stages of the vegetative life cycle. Our investigations clearly show that mitochondria have a relatively wide range of sizes, within certain limits, and vary like the mitochondrial shapes; in fact, they vary in various cells at various stages as well as in several cells at the same stage and even in one and the same cell. Thus, we present a plastic insight into the dynamically changing micromorphology of the mitochondrial population in Chlamydomonas reinhardii.