This is a study, by electron microscopy, of the structure and possible function of a “dense wall” in the pollen mother-cells (PMC) after the last mitosis, carried out on Allium cepa anthers. On the formation of the “special callose wall”, the paper also describes the contribution of the membranes from vesicular elements to the formation of a new plasmalemma closely related to the “special callose wall”, and the formation of this layer from the inner contents of vesides which are of nuclear origin and other vesicular elements.
A fine structural study of spermatozoa of the scorpion Tityus bahiensis demon-strates a male gamete which diverges from typical cells by the underdeveloped acrosoma and 9+0 pattern of the flagellum. The overall organization of this cell follows a helical pattern.
Detailed cytological investigations in Lens esculenta var. microsperma and macrosperma have been carried out. Mitotic and meiotic irregularities have been observed. Seven and fourteen have been found as haploid and diploid chromosome numbers respectively. No significant morphological difference in the chromosomes of two varieties could be noticed. Karyotype has been analysed and found to be asymmetrical and belong to 2b type according to Stebbins (1958) classification. Two pairs of satellited chromosomes have been recorded for the first time. Mitotic irregularities in the form of chromatin bridges, fragments and laggards have been observed in L. esculenta var. macrosperma. High temperature seems to be mainly responsible for their occurrence. Meiotic abnormality in the form of inversion bridges at anaphase I have been noticed in L. esculenta var. microsperma. Pollen sterility in both varieties have been worked out.
1. High germination percentage of the seeds of both the species was obtained by keeping the seeds in a mixture of half sand and half clay at a temperature of 20°C±1. 2. Good preparations were obtained by pre-treating young root tips of Cori-andrum and Cuminum with saturated aqueous solution of paradichlorobenzene and 0.002 M aqueous solution of 8-hydroxyquinoline, respectively. 3. The diploid chromosome number in Coriandrum was 22 and in Cuminum it was 14. Idiograms of the somatic karyotypes of the two species are given. 4. Karyotypes of both the species and their interrelationship are discussed.
Fifteen varieties of Cajanus cajan (L.) Millsp differing in morphological chara-cteristics and Autylosia lineata W. and A. were studied for karyomorphology. Twenty-two chromosomes were found in all the varieties of Cajanus cajan and Auty-losia lineata. Considerable inter varietal variation in chromosome complement was observed, in regard to arm ratio, total length etc. Variability in morphological characters observed among the cultivars of Cajanus cajan is expressed to some extent through variation in its karyotype. One pair of satellited chromosome was observed in 13 varieties of Cajanus cajan and Autylosia lineata. A variety P.958 did not have satellited chromosome, while variety NP.69 had a heteromorpho-logical pair with one member being satellited only. Variety T.21 had shortest total chromatin length of 27.60±0.142 microns against 44.92±0.795 for variety R.3. It was 26.36±0.848 for Autylosia lineata. On the basis of arm-ratio the chromo-somes were catagorised as median (0.76-1.00), submedian (0.51-0.75) and sub-terminal (0.25-0.50).
The chromosome number of 25 Australian species of the land snail family Camaenidae, including members of the genera Exilibadistes, Chloritobadistes, Cupedora, Meracomelon, Meridiolum, Glyptorhagada, Semotrachia, Sinumelon, Pleuroxia, Xanthomelon, Sphaerospira, Bentosites, Parglogenia, Torresitrachia, is n=29.
The paper deals with the cytology of 28 species of fodder grasses of the W. Himalayas based on meiotic studies. Five species have been investigated for the first time. Two new races have been discovered in the species already investigated. Intraspecific variation has been noticed in Avena fatua (n=7, 14), Bromus japonicus (n=7, 21), Dactylis glomerata (n=7, 14), Festuca undata (n=14, 21) and Poa bulbosa (n=21, 2n=50). Taxonomic status of the polyploid races is briefly dis-cussed.
This report gives the results of cytological investigations on 23 species of West Himalayan Panicoideae which include many of the important pasture grasses. Chrysopogon echinulatus (n=10), Erianthus versicolor (n=10) and Pennisetum lana-tum (n=9) have been cytologically reported for the first time. New cytological races are found in Bothriochloa ischaemum (n=10), Capillipedium parviflorum (n=11) Cymobopogon distans (n=10), Themeda anathera (n=10), Digitaria bicornis (n=27), and Pennisetum flaccidum (2n=45). Our present observations confirm our pre-vious conclusions of the occurrence of a number of cytological intraspecific races of grasses in the Himalayas.
Cytogenetic findings in a malignant effusion of ovarial origin are presented. Karyotype analysis revealed the existence of several cell lines. The relationship between these lines has been established by the study of the marker chromosomes; the cells belonging to the minor lines arose by polyploidization from the major line cells. These data support the concept of the single cell origin of various cell lines in human tumors.
A hybrid, between Arachis hypogaea and A. duranensis was obtained. Study of meiosis revealed a maximum association of 10 bivalents and 10 univalents at meta-phase I. This shows that one genome is common in both the species supporting the alloploid origin of cultivated species. The hybrid was completely sterile with high degree of pollen sterility. Attempts are being made to transfer resistance for tikka leaf spot disease from A. duranensis to A. hypogaea.
A cytological study of nine fulgorid species revealed that they had similar get up of oogonial and spermatogonial chromosomes. Chromosomes were bean-shaped with a large pair while the remaining were gradually seriated. In the gonial complements one sex chromosome in males and two in females showed no differ-ential behaviour compared to the autosomes. The diploid number in female and male gonial complements was 20 and 19 respectively in Oliarus hodgarti; 26 and 25 in Barunoides albosignata; 28 and 27 in Diostrombus carnosus, Pyrilla pusana, Ricania zebra, Eoeurysa flavocapitata; 30 and 29 in Dictyophara pallida, Elasmocelis platypoda, Varma distanti. The behaviour of spermatocyte chromosomes in all the above species was of orthodox nature with the single X chromosome showing heteropycnotic behaviour in prophase I. The first division was reductional and the second equational. The chiasma frequency was generally one per bivalent except the large bivalent which sometimes had two. Relative percentage volume of the chromosomes was deter-mined from metaphase I. Results obtained in this investigation have been correlat-ed with the published data and the probable mode of evolution in the group has been discussed.
The pattern of RNA synthesis during meiotic prophase has been investigated in Ornithogalum virens. The rate of RNA synthesis fluctuates depending on the stage of meiosis. Nucleolar RNA synthesis continues at a low level throughout meiotic prophase. Evidence is presented which indicates that a greater percentage of the newly synthesized RNA is being transported to the cytoplasm in pre-pachy-tene stages as compared to cells in pachytene or diplotene of meiosis. The effects of actinomycin D on the morphology of the meiotic cells are also described.
Bei 20 Inzuchtratten wuchsen subcutane fötale Magenzelltransplantate zu Organoiden, die hinsichtlich des Wandaufbaues and der Funktion dem Magen vergleichbar waren. In 8 Fällen wurde nach 150 Tagen das Empfängertier durch Freisetzung endogenen Histamins geschockt. Transplantat- und originärer Magen wurden anschließend untersucht, wobei sich in beiden Präparaten neben den klassis-chen sekretionstypschen Merkmalen eine Zunahme des Cytoplasmavolumens, Vakuolisation, lakunenartige Dilatation der Golgi-Zisternen und vollständiges Verschwinden des endoplasmatischen Reticulums fanden. Insgesamt lassen sich die Befunde auf eine markante Histamin-Reaktion zurückführen. Schockbedingte Mikrozirkulationsstörungen treten dagegen kaum in Erscheinung. Derartige leicht zugängliche Magenzelltransplantate scheinen für bestimmte pathophysio-logische Untersuchungen nützlich zu sein.
Cytological studies of a genetic stock of pearl millet is being reported here. On the average 1.934 bivalents were observed as compared to seven bivalents in normal. Meiosis was irregular leading to unequal distribution of chromosomes and laggards. Pollen fertility was 38.4%. Complete to partial seed sterility was also observed.
The triploid M. charantia raised by hybridisation between the tetraploid and the diploid show highly irregular meiosis with 5 to 11 bivalents and 0 to 6 uni-valents. The pollen fertility is 38.7 %. The triploid did not set any fruit. The appearance of various sex forms obtained by colchicine treatment of the monoecious diploid M. charantia has indicated the possibilities of understanding the sex mechanism in this species and related species. The resulting variants from the treated materials which remained diploid showed three types of sex expression, namely, Andromonoecious, Gynoecious and Trimonoecious. These intermediate sex forms are phenotypically, similar to those in the genus Luffa and are likewise unstable.
The meiotic behaviour of two X-ray induced Pisum mutants was analysed which show a high degree of chain and ring formation as a consequence of a high number of translocations. The characteristic feature of both these mutants is that all the PMCs do not show the same type of configuration; on the contrary, a pattern of different configurations is present. Both the mutants display a similar meiotic behaviour but they differ considerably with regard to their seed production. In both cases, a kind of “repair mechanism” seems to become effective in different manner which leads to an unexpectedly high degree of fertility.
The paper reports a comparative chromosomes study of six species of Crasso-strea and three of Ostrea. Of these, six species occur in Karachi, West Pakistan and three on the Pacific coast of the U.S.A. Chromosomes of 18 males and 92 females were examined from germ-line cells and early embryonic mitoses. Meiosis was found to be chiasmate and photographs of first metaphase biva-lents of spermatocytes are being published for the first time. A 2n=20 (n=10) is common to all oysters. Karyotypes contain only metacentric (M) and sub-metacentric (S) chromosomes and are symmetrical and outwardly identical. Fluctuations were observed, however, in the frequencies of M and S elements in different species and have been attributed to pericentric inversions or centric shifts.
Cytological, embryological and hereditary behaviour of twenty six collections of Apluda mutica L. var. aristata (L.) Pilger are reported. Ten accessions were diploids with n=10 chromosomes. Meiosis in these accessions was regular with the formation of 10 bivalents at diakinesis and metaphase I and with a regular distribution of 10 chromosomes to each pole at anaphase I. Embryo sacs were usually 8-nucleate, and 4-nucleate embryo sacs were rare. Out of the other 16 accessions, 10 were hexaplids with a chromosomal count of n=30 and 6 were heptaploids with n=35. Meiosis in these accessions was irregular with multivalent chromosome associations at diakinesis and metaphase I, laggards at telophase I and telophase II and pollen tetrads with micronuclei. In all the asseccions of the two polyploids races, both 4-nucleate and 8-nucleate embryo sacs were encountered. The mechanism of apomixis is pseudogamous apospory. It is concluded that Apluda mutica represents a polyploid complex with 2n chromosome numbers ranging from 20 to 70, the diploids being largely sexual and the polyploids being facultative apomicts.
The chromosome number of four wild plant species grown in Kuwaiti desert was determined from PMCs during microsporogenesis. Two species belong to the family Compositae namely, Picris sahara, Senecio desfontainei, and two species belong to the family Plantaginaceae, namely, Plantago boissieri and Plantago ciliata. Meiosis was regular in all species studied, but with low chiasma frequency per bivalent at diakinesis. B-chromosomes were found in Senecio species. Chromo-centres were also found in the interphase stage of the somatic cells for the same species.
1. Cytological determination and sex chromosome mechanism of some seven species of Coleoptera belonging to four families have been made. 2. The general plan of meiotic division is uniformly similar in most of the studied species, first division being reductional and second division being equational for all the chromosomes. 3. The sex chromosomes show heteropycnotic behaviour during different stages of meiosis. Sometimes they take peculiar shape and size. 4. In first division, the bivalents are mostly rod-like. 5. The sex chromosomes show different types of configurations viz. Xy, Xyp, Xyr, and XO. 6. The chromosome number in most cases tallies with the type number i.e. 2n=9AA+XY. 7. In some cases chromosomal polyploidy and polymorphism have been encounter-ed. 8. The probable mechanism of evolution in the number of chromosomes has been discussed in the light of chromosomal structural changes.
The present study deals with the nucleolar structure in primary spermatocytes of some Drosophila species. The nucleoli in living spermatocytes show a dark area (basophilic area, composed by “pars granulosa”) attached to the nuclear envelope, an oblong area with intermediate optical density (argentophilic area, formed by “pars fibrosa”), and small light regions which appear as vacuole-like areas. This segregated morphology in Drosophila spermatocytes allows to correlate the nucleolar architecture at the light and electron microscope level.