Detailed cytological studies were made in 3 grape varieties viz., Mission, Muscat of Alexandria and Selection 94. The somatic number of chromosomes is 38 in all the three varieties. The lengths of chromosomes varied in between 2.163 to 0.596 microns. All the chromosomes were classified into median and sub-median. Mitosis was normal. Meiosis was normal but for minor abnormalities. In all the 3 varieties 3 bivalents were associated with nucleolus. Occurrence of lagging bivalents is the only abnormality in meiosis. Meiotic index was 100% in Mission and Selection 94 where as in Muscat of Alexandria it was 84%. Since Mission and Selection 94 are cytologically stable they can be safely utilized in the breeding programme without hindrance.
A cytological study of Cerastium arvense L. in North America has been carried out using plant material from most of the range of the species. Chromosome counts of 2n=36, 72 and 90 were obtained. The single population with 2n=90 is a hybrid. Counts of 2n=72 and 90 are new for C. arvense in North America. Meiosis was regular in all the plants in which it was studied except in the hybrid and in a few cells of C. arvense ssp. maximum from Cannon Beach, Oregon. The diploid and the tetraploid can be separated by several morphological features including leaf shape, length of stomata, diameter of pollen and length and breadth of seeds.
Comparative analysis of chiasma frequencies and terminalization in sixteen Fl hybrids of T. durum and T. dicoccum with nine species of 4n Triticum have been studied at late diplotene/diakinesis and metaphase. Total number of chiasmata per cell was found to be maximum in T. durum×T. dicoccoides at late diplotene and in T. durum×T. dicoccum at metaphase. Variations in the number of bivalents with 0 to 5 chiasmata have also been studied at diplotene and metaphase. As many as five chiasmata per bivalent were noted in T. durum×T. dicoccoides. Similarly maximum number of bivalents with 4 chiasmata was observed in T. dicoccum×T. persicum at diplotene. This suggests random distribution and relatively lesser linear differentiation among the parental species. At metaphase maximum number of bivalents with 4 chiasmata was confirmed in T. durum×T. dicoccoides. On the contrary, highest number of univalents was noticed in T. dicoccum×T. durum (apart from T. timopheevi combinations). Maximum terminalization was observed in T. dicoccum×T. polonicum. Correlation coefficients between total bivalents length and total number of chiasmata per PMC have also been worked out for both the stages. Significance of these values at 0.05 or even 0.01 level has been noted in some combinations. These comparative studies suggest that there are variations in respect of linear genetic differentiation among the corresponding parental homologues. This may indicate relative gradations of affinities or differences among species of 4n wheats.
The mutagenic activity of manganese ions when applied either alone or in various combination with two alkylating mutagens, ethyleneimin and propane Sultone were studied using dormant seeds of pea as a test material. The criteria for measuring the biological damage were seed lethality, seedling injury, mitotic and meiotic chromosomal aberrations and the frequency of leaf spots on first two leaves of the seedling. Mn++ by itself does not cause much seed or seedling injury but produces a moderate amount of chromosomal aberrations with a corresponding increase in the frequency of leaf spotting. When El treatment were accompanied by Mn++ there was an overall reduction in the biological damage caused by El alone, where as when Mn++ was given prior to PS treatment, there was an overall increase in the damage caused by PS alone. A positive correlation was found between chromosomal aberrations and the frequency of leaf spotting. Data have been discussed with special reference to the probable mode of action of manganese ions and its influence on the activity of other mutagens.
The frequency of chromosomal interchanges has been assessed in terms of multivalent associations in self-incompatible and self-compatible Brassica campestris L. var. dichotoma Watt. (cv. Brown Sarson) after irradiation of dry seeds with gamma rays and thermal neutrons. The chromosomal interchanges showed a linear dependence on doses of both these types of irradiation. Gamma rays, compared to thermal neutrons, induced a slightly higher order of segmental interchanges. Pollen and ovule sterility were conditioned by the number and frequency of participating chromosomes. Most multivalents were interchanges of a chain of four chromosomes. Interchanges involving two pairs of non homologous chromosomes were higher in frequency than those involving more chromosomes. Self-compatible types showed a higher degree of resistance to radiation. Apart from interchanges, other aberrations like univalents, laggards, bridges with fragments, unequal anaphase I separation and chromosome stickiness were also observed in low frequency.
1. In den Wurzelspitzen (vermutlich überwiegend sproßbürtigen Adventivwurzeln) der stammsukkulenten Stapelieen (Asclepiadaceae) tritt relativ häufig Polysomatie auf. Ihr Ausmaß, beurteilt nach Querschnitten, läßt verschiedene Abstufungen erkennen: a) Die Zellen mit verdoppelter Chromosomenzahl finden sich einzeln oder zu wenigen; b) größere Komplexe von ihnen verleihen den Wurzeln den Charakter von sektorialen, meri- oder periklinalen Cytochimären. c) Verschiedene Wurzeln einer Pflanze haben entweder die taxonspezifische Chromosomenzahl oder eine um das Doppelte erhöhte; in diesem Falle ist nicht die Wurzel polysomatisch, sondern die Pflanze. 2. Die Polysomatie ist bereits in den Initialen des Apikalmeristems nachweisbar, macht sich also nicht erst beim Übergang von der Teilung zur Streckungszone bemerkbar. In den Teilungsphasen der Zellen mit verdoppelter Chromosomenzahl wurden niemals gepaart liegende Chromosomen beobachtet. 3. Entgegen der üblichen Deutung, daß die Polysomatie in der Regel als Folge einer Endopolyploidisierung im Zuge der Zelldifferenzierung in dem betroffenen Organ selbst zu verstehen ist, muß für die Stapelieen angenommen werden, daß sich bereits an der Bildung der Adventivwurzelprimordien mehrere Zellen unterschiedlicher Kernvalenz beteiligen, die teilweise schon im “Mutter”-Organ Endomitosen durchgemacht haben. Die Primordien werden in der Region des Außenphloems angelegt. 4. Außer der “regulären” Polysomatie werden zwei Fälle beschrieben, in denen die erhöhte Chromosomenzahl einer Verdreifachung des Ausgangswertes entspricht.
The phylogenetic relationships between D. bifasciata and D. imaii have been established through inversion analysis of the hybrids. The analysis of salivary gland chromosomes has revealed that D. imaii differs from D. bifasciata by three inversion steps involving at least in two chromosomes (two in the second chromosome and one in the third chromosome). Furthermore, the comparisons of the intraspecific chromosomal polymorphisms has resulted in the finding that the Italian and Swiss strains of D. bifasciata occupy an intermediate position in the evolutionary history between D. imaii and the Japanese strains of D. bifasciata.
The effects of ionizing radiations (X- and gamma rays) and chemical mutagens (EMS and DES) on chromosome association and chiasma frequency were studied in the M1 plants of Sorghum purpureosericeum (2n=10) raised from the treated seeds in comparison with control. Of the treatments, radiations induced a high frequency of translocations as well as univalents compared to the treatments with chemical mutagens. The frequency of translocations showed an increase at higher doses of radiation treatments. There was, in general a decrease in the frequency of chiasmata in the treated plants compared to the control plants excepting 9.70 mM EMS. Radiation treatments caused more decrease in the chiasma frequency as compared to the treatments with chemical mutagens. In contrast to the reduction in the number of bivalents with three chiasmata per bivalent, the number of bivalents with single chiasma increased in the treated plants when compared to the control plants. The mechanisms of forming chiasmata are discussed in the light of present investigation.
Exposure of Allium sativum root tip cells to digitonin prevents the formation of conventional microtubules and thus the assembly of a functional mitotic spindle. With the appearance of arrested meta-anaphase stages, however, a new tubular element (480 to 520Å in diameter) appears among the scattered chromosomes. These large “macrotubules” are randomly distributed within the sections in groups of several closely associated tubules. Cross linkages similar to intermicrotubule bridges are regulary found. Tubules intermediate in size between the macrotubules and the occasionally encountered conventional microtubules are not observed. These macrotubules, like microtubules, possess a wall thickness of approximately 60 to 70Å. Attempts to demonstrate filamentous subunits or microcylinders within the wall of these tubular elements were unsuccessful. In cross-section, a centrally located electron-opaque material is often discernible within the lumen of many of these macrotubules. Since such macrotubules were not observed in dividing untreated cells, it seems probable that they are the digitonin-induced polymerization products of tubulin. The presence of these oversized tubular elements further sup-ports the hypothesis that functionally separable microbutular systems may be different chemically and architecturally.
We have studied the replication in the marker chromosomes of a hypertriploid mouse ascites tumour. Tritiated thymidine has been used, followed by the autoradiographic process, to determine the marked portions ofthe chromosomes in the later replication periods and time during which the chromosomes are synthesizing complementary DNA. The metacentric chromosome terminates replication in the terminal and proximal regions of the arms. There is no ordered sequence in the DNA replication in this chromosome. Two minute chromosomes replicate the complementary DNA early and syn-chronically, and the third replicates later. The intensity of silver gains differs in these 3 chromosomes, at a determinate experimental hour when all our marked. The maximum number of marked chromosomes, and the maximum intensity of silver grains per chromosome appears during the early replication periods.
Twenty-nine bivalents were found in the PMCs of Euryale ferox from Gorak-hpur, Eastern India. Primary and secondary association was noted at diakinesis and metaphase respectively. Secondary association at metaphase I both from equatorial and polar views showed the formation of quadrivalents, hexavalents, and octavalents in descending order of frequency. The phenomenon persisted even at metaphase II. Presence of strong secondary association in the species suggests its gametic number to have originated secondarily by means of allopoly-ploidy.
Trypsinised cells and explants from human breast carcinomas (one of which proved to be normal tissue) were set up in culture. A variety of media and additives (hormones etc.) were used to stimulate vigorous cell growth. The trypsinised cells failed to grow but in seven of the twelve tumors, the explants grew successfully for a period of at least five weeks.
The karyotype analysis of ten species of Membracidae (Homoptera) showed the oogonial and spermatogonial chromosomes as bean shaped and gradually seriated elements. Sex chromosomes were two in the female and only one in the male but these did not exhibit any staining difference compared to the auto somes. The diploid number in female and male complements were 22 and 21 respectively in Oxyrachis tarandus, Oxyrachis sp., Leptocentrus substitutus, Otinotus elongatus, Otinotus sp. and 20 and 19 in Tricentrus albomaculatus, Tricentrus sp., Gargara contraria, G. flavolineatus, Cocosterphus decoloratus. The pattern of meiosis in males of the species investigated was very conservative type. There was a faint “bouquet” at the early primary prophase. The first division was reductional while the second equational. The sex determining mechanism was XX: XO in all of them. The 19 chromosome species were character-ised by a huge autosomal bivalent. The relative percentage volumes of the chro-mosomes was determined from primary spermatocyte metaphase plates. In the light of the data published by earlier workers and the results obtained in this investi-gation, the probable mode of evolution in the group has been discussed.
Endothelium lines the inner surface of the canine aorta as a pavement of flattened cells. In the intercellular junction, there are regions where the adjacent membranes are quite dense and appear rather firmly attached to each other. The cytoplasm has the usual content of organelles: mitochondria, smooth or rough elements of endoplasmic reticulum, Golgi complex, centrioles. A characteristic feature of the endothelial cell is a large number of vesicles, either smooth or coated, scattered throughout the cytoplasm. Large numbers of solid cytoplasmic filaments (diameter of 40 or 75Å) and microtubules (230Å in diameter) are also found in the endothelial cells. Tubulated bodies approximately 0.1μ in diameter and up to 0.3μ in length are sparsely scattered within the cytoplasm. Unusual membrane-bound large microtubular bodies 0.5-0.8μ in diameter are also found. Crystalline structures are present in aggregates. It has a periodicity in the range of 130-180Å.
Cytomorphology of the spontaneous triploid in Capsicum annuum has been studied. Comparative karyomorphology of diploid and triploid revealed marked differences in respect of growth habit, pollen fertility and floral characters as seen from the increased plant parts, delayed growth and prolonged flowering in the triploid. Colour of the fruit and its nature do not show much difference, but marked difference is seen in fruit size and in the ratio of healthy and sterile seeds. Cytology of the triploid reveals that it is an autotriploid. Meiosis in triploid has various chromosome associations like univalents, bivalents and trivalents 1 to 11, 1 to 6 and 6 to 12 respectively. Quadrivalents were observed in a few cells. Fertility is poor in the triploid and an aneuploid with 2n=26 chromosomes was obtained from the triploid progeny.
DNA synthesis has been studied with TH3 in the terminal S stage of the species O. americanus (2n and 4n), O. cultripes (2n), and the artificial triploid hybrid of O. cultripes×O. americanus. A slight asynchrony was observed between homo-logues, more accentuated in the tetraploid and in the triploid species. Chromosomes of either late or early replication were not observed. Variations in the G2+P period in mitotic cells were observed in all the species, always of a longer duration in gonads. The satellites in pair 11, present in all species studied, are early re-plicating, but the satellite of pair 4 in O. americanus 2n, is late replicating.
In this investigation an attempt was made to find the cause of restricted oc-currence of natural polyploids in the genus Iberis, (Cruciferae) and efforts were made to see if aberrant types with extra chromosomes could be obtained and stabilised by polyploidization. Three methods using colchicine were compared in treatments involving seven species viz. I. amara gp. (I. amara varieties and I. odorata), and I. pectinata, all annuals with chromosome number 2n=14; I. welwitschii and I. bernadiana both perennials with 2n=14; I. umbellata an annual with 2n=18 and I. sempervirens a perennial with 2n=22. In the annual species (2n=14 and 18), a high proportion of polyploid tissues was induced in mixoploid C1 plants. The treated perennials (2n=14 and 22) failed to flower and could not be assessed for polyploidy. In the subsequent generation or C2, only I. umbellata produced a high number of reasonably stable tetraploid plants. Triploid seeds were obtained from C1 plants and from crosses between 4 n female plants and 2 n males in I. umbellata, while the reciprocal crosses gave only diploid seeds or failed. No aberrant types with extra chromosomes were recovered from the triploid or other generations. Cytological abnormalities were observed which may help to explain instability of polyploids in nature, but it is believed that there is a strong genetic control factor which acts to spontaneously reduce polyploid genomes to haploid ones. Tolerance to higher ploidies appears to increase with change in basic numbers from x=7 to x=9 to x=11.
Onion root-tips were used to study the effects of water-soluble extract of tobacco smoke condensate (TSC) on various cytological parameters. When roots were treated with different concentrations of TSC (0.04%, 0.1%, 0.05% and 0.25%) a number of abnormalities resulted. These included vacuolization of the cytoplasm as well as abnormal mitotic stages. The abnormalities consisted of scattering of chromosomes during metaphase, and bridging during anaphase. Also with in-creasing concentrations of tobacco smoke condensate, the mitotic index declined. This investigation should be of importance in assessing the biological effects of tobacco smoke and its constituents.
At pachytene all the seven bivalents could be followed in well spread cells. The chromosomes length varied from 24.76 micron for the shortest to 48.41 microns for the longest. Centromeres are not easily discernible, these are spotted out as small gaps flanked on either side by deep stained regions. The nucleolus organizing chromosome is the shortest and the nucleolus is conspicuous at pachytene. The nucleolus organizing region is almost terminal.
Primary spermatocytes of mice respond to asafoetida by production of structural chromosomal aberrations. The effect is of the delayed type. Very high concen-trations of asafoetida do not result in a corresponding linear increase in aberration frequency. Spontaneously arisen polyploid cells in the animals used showed very few abnormalities as compared to the other cells. Females kept for mating with treated males failed to produce a progeny after the 15th dose to the male. Chro-mosomal damage by asafoetida may be due to 7-hydroxycoumarin present in its resin.
A cytogenetical study of four species of the genus Gobio that live in Rumania results in that 3 species, G. gobio, G. kessleri banaticus and G. albipinnatus vladykovi have the same number of chromosomes (2n=50) and chromosomal arms (NF=98), in despite of their distinct chromosomal complement. The fourth species, G. uranoscopus is different in the number of chromosomes (2n=50) and chromosome arms (NF=100), thus justifying the establishment of the subgenus Rheogobio.
The paper deals with polysomaty in thirty nine species and varieties of Liliales, collected from different parts of India. The polysomatic behaviour has been shown to involve the occurrence of struc-turally and numerically altered chromosome complements in the somatic tissue along with the normal complement. Aneuploid and polyploid variations as well as the zone of occurrence have been recorded. It has been inferred that both non-disjunction as well as endomitotic reduplication involving all or a few chromosomes of the set are responsible for such poly-somaty. Evidences show that fragmentation and translocation are responsible for structural alterations. Of the numerical and structural alterations, it has been deduced on the basis of the data, that the latter plays a more important role in the origin of new geno-types as compared to the former. Genes susceptible to minute change in cell en-vironmental balance are selected and maintained in this category of plants. Heterochromatic regions which are more susceptible to environmental effects are mostly involved in structural alterations. The suggestion that the nucleo-cytoplasmic balance at the tissue rather than at the individual cell level is maintained in this category of plants, has been supported. Here, the absence of balance at the individual cell level is advantageous as it provides the basis for irregular chromosome behaviour and somatic mutation.