The autotetraploid form of Psidium guajava, L. reveals highly irregular meiotic division. It shows multivalents, abnormal distribution of chromosomes at anaphase, equatorial disjunction of a laggard, spindle fusion during second meiotic division, formation of stray chromosome and micronuclei. Mode of origin of this polyloid and its sterility have been discussed.
Psidium freidrichsthalianum Niedenzu is a diploid species having a chromosome number 2n=22. Quadrivalent, trivalent and univalent have been observed concomitant with bivalents. In addition to this dicentric bridges accompanied by framgent have been seen. It is presumably the consequence of inversion crossing over at the preceding diplotene. Beside these, other abnormalities such as precocious disjunction, unequal separation, lagging chromosomes, spindle fusion and stray chromosomes have been recorded. Pollen fertility is 50 per cent.
The detailed cytogenetical studies have been undertaken in fifteen species of genus Phaseolus, Linn. for the first time to determine the chromosomal basis of speciation and evolution. Cytogenetical investigations in 15 species of Phaseolus wild and cultivated so far studied revealed the somatic chromosome number to be 2n=22 (except wild allotetraploid Phaseolus species 2n=44). The somatic chromosomes are small, their size range from 0.85μ to 3.0μ. The longest being 3.0μ in P. vulgaris and shortest in 0.85μ in P. ricciardianus. Though the chromosome number of all the species is same they differ from each other in certain karyotypic details. This is of great significance in the origin of new taxonomic units. Inversion heterozygosity has been observed in five species. The number of such bridges are either one or two. The role of both pericentric and paracentric inversions in the evolution and origin of species has been quite significant. The univalent chromosomes occur in six species. The average of univalents per PMC range from 1.68 (P. bracteatus) to 0.96 (P. trilobus). The role of genetical factors, precocious separation, inversion heterozygosity, desynapsis and environmental factors such as change in temperature are to a great extent responsible for the appearance of univalents in different species of Phaseolus. Pollen sterility appears to be fairly low among various taxa of Phaseolus. The percentage of pollen sterility ranges from 18% (P. semierectus) to 3% (P. acutifolius and P. aconitifolius, etc.). Inversion heterozygosity and presence of univalents have been emphasized as the main causes of pollen sterility. Evolutionary trend in the genus Phaseolus has been studied. Polyploidy has not played any significant role in evolution. Structural chromosomal changes as pericentric and paracentric inversions, gene mutations, hybridization and weak development of isolation mechanism have dominated the evolutionary history in the genus phaseolus.. Diminution in the size of chromatin material with advancing evolution has been a special feature. Species with symmetrical karyotypes having large chromosomes with median primary constrictions are primitive while those with asymmetrical karyotypes having smaller chromosomes with subterminal primary constriction are regarded as advanced. Phaseolus vulgaris and P. aureus with large somatic chromosomes and longest total chromatin length has been considered primitive respectively in climbing and erect habit series of Phaseolus species. While P. bracteatus and P. ricciardianus with short chromosomes and shortest total chromatin length are considered as advanced in climbing and erect habit series respectively. Presumably climbing habit Phaseolus species are ancient and erect ones are modern. It is thus concluded that Phaseolus vulgaris which is under cultivation in Mexico for the past 7000 years is primitive and it has given rise to other Phaseolus species including erect ones.
Detailed cytogenetical investigations in Pongamia pinnata (L.) Pierre, a monotypic genus, have been carried out. Eleven and twenty-two have been found to be as haploid and diploid chromosome numbers respectively. The plants have been reported to be an heterozygote for both inversions and translocations. Meiotic abnormalities in the form of quadrivalents at diakinesis and metaphase I and chromatin bridges at metaphase II are recorded for the first time in this plant. The basic chromosome number and high pollen sterility have been discussed. Pollen sterility is clearly chromosomal in nature and caused by deficiency and genic unbalance in the microspores.
Chromosomes from the vole mouse Akodon dolores and from laboratory mouse showed the presence of G-bands after 3 minutes digestion with trypsin and Giemsa stain. Simultaneously, 30- to 40% of the interphase nuclei exhibited a dark ring parallel to the nuclear contour and a radial array of the chromatin in the internal and external regions of the ring. The origin and meaning of this ring image was analyzed by combining progressive trypsinizations with other methods such as C-banding procedures, autoradiography with 3HTdR, staining with quinacrine mustard and 33258 Hoechst fluorochromes. Moreover, the presence of the dark ring was also investigated in cells treated with actinomycin and in control cells not subjected to any treatment. The results obtained allowed to assume that in interphase nuclei the chromosomes have chromatin bridges which connect the dark G-bands and that these bridges are probably involved in maintaining an ordered architecture of the nucleus with fixed chromosome positions in regard to the nuclear envelope and in regard to other chromosomes. Trypsinization produces a disruption of the interphase chromatin arrangement and the subsequent appearance of a dark ring formed by the combination of constitutive heterochromatin and dark G-bands.
Estimation of chromosomal aberrations in flowers of Lens culinaris according to their sequence of development in the plants at 4, 8 and 12 Kr in the MI generation, showed that the later formed flowers had smaller percentages of cells with aberrations than those developed earlier. It is suggested that this may be the result of competition between more damaged and less damaged cells during the development of the shoot. There is consequently a decrease of sterility in successive flowers. The numbers of karyotypes taking part in the formation of lower and uppermost flowers were estimated cytologically at 4, 8 and 12 Kr. It was found that more karyotypes were involved in the formation of the lower flowers than in the upper ones. It appeared that at lower doses larger numbers of karyotypes were taking part in the formation of the chimaera than at higher doses.
All varieties under study showed varied degrees of sensitivity for different characters, namely, survival, meiotic aberrations and pollen and spikeley sterility to gamma irradiation and less sensitive to EMS treatment. In gamma treatment the wild species O. spontinae exhibited the highest resistance for M1 injury, whereas the japonica (Norin-27) recorded the lowest and the rest are recorded intermediary values. There were no marked differences in frequency of chlorophyll mutations in gamma and EMS treated population. Within gamma treatment, frequency and spectrum of chlorophyll mutations, it was almost same in high and low fertility groups. However, EMS treated population recorded remarkable differences in frequency and spectrum of chlorophyll mutations in both the fertility groups. In general EMS was found to be most efficient and effective mutagen at high fertility level than gamma treatment.
Thirty-one species and varieties of 8 North-Indian Convolvulaceous genera were investigated. Normal diploid like meiotic behaviour was evident in most of these. Polyploid nature of Ipomoea batatas and some desynaptic bivalents in Merremia aegyptia accounted for aberrant meiosis. Some desynaptic bivalents were also observed in I. bonanox, Porana paniculata and Calystegia hederacea. Ipomoea chryseoides (n=15), I. mutabilis (n=15+O-1B), I. dichroa (n=15), I. palmata (white flowered type n=15+1B) and Argyreia campanulata (n=14) represent first chromosome counts for these species. Lowest and highest chromosome numbers n=9 and n=45 were encountered in Jacquemontia pentantha and Ipomoea batatas respectively. Poor incidence of polyploidy may either be due to a meagre cytological coverage or the secondary nature of the high basic numbers met in the family. Aneuploidal relationship of the different species/genera is evident. Importance of aneuploidy and polyploidy in the evolution of Convolvulaceae is discussed. Morphological variability in Ipomoea aquatica, I. eriocarpa, I. fistulosa, I. palmata and I. pestigridis seems to be correlated with the cytological features.
Meiotic studies have been carried out in 10 species and 6 varieties. The different chromosomal associations have been analyzed, total and terminalized chiasmata counted and half chiasma per chromosome calculated. Regular bivalent formation has been observed in all the taxa. Number of bivalents ranges from 9-36 in various genera. A high number of rod bivalents has been counted in Coriandrum sativum. Pollen variability is evident in only one of the genera. Occurrence of a high number of rod bivalents and less number of chiasmata in Coriandurm sativum has been suggested to be due to inversion in the chromosomes. Autoploidy might have been responsible for the evolution of Hydrocotyl javanica. Certain changes in the groupings of various tribes of subfamily Apioideae has been suggested on the basis of the cytological studies.
We have carried out karyologic studies on Spanish ecotypes and Australian cultivars representative of the three subspecies of Trifolimu subterraneum L. (ssp. brachycalycinum Katzn. et Morley; ssp. subterraneum; ssp. yanninicum Katzn. et Morley). The analysis of the karyotypes of the eight taxa studied shows significant karyotypical differences among the three subspecies in question. These results confirm the speciation studies on T. subterraneum L. by Katznelosn et Morley (1965 a and b) and Katznelson (1974).
1. Meiosis was studied in 29 collections belonging to 18 Setaria species. These included nine diploid collections belonging to nine species, fifteen tetraploid collections belonging to nine species and five hexaploid collection belonging to four species. 2. The diploid collections had 2n=18 except in S. homonyma where 2n=20 was observed. The tetraploid collections had 2n=36 and the hexaploids had 2n=54. 3. Meiotic irregularities in some polyploid collections were described and discussed. 4. Setaria alnaspicata, S. gerardi and S. palmata were cytologically examined for the first time; new counts were found in S. chevalieri snd S. homonyma. 5. Chromosomal races in S. sphacelata, S. pallide-fusca and S. verticillata were described and discussed.
For histochemical investigations of fruit pulp, before fixation tissue should be dehydrated in absolute alcohol at dry ice temperature (-78°C) to avoid cell shrinkage. Cell wall polysaccharides can be removed selectively without section losses provided the sections are mounted on slides coated with a solution made with 0.5g gelatin, 0.2g chrome alum and 100ml H2O. Pectic acids are removed by overnight pectinase treatment at 30°C, followed by 2 hrs in 0.5% aqueous ammonium oxalate at 90°C. Hemicellulose and noncellulosic polysaccharides are removed by 12 hr treatments respectively with 4% and 17.5% aqueous NaOH at room temperature, with slices kept affixed by a coating made up by dipping the slides into a 0.5% ethyl cellulose solution in a 4:1 mixture of toluene and absolute ethanol. After the extraction the coating is dissolved away and periodic acid Schiff staining is subsequently used to detect and evaluate remaining cell wall polysaccharides.
A diploid apomict, in addition to the already known triploid apomict is described from the W. Himalayas in the widely ranging species Adiantum lunulatum Burm. On the basis of morphological evidence it is suggested that the whole complex be split up into two, viz., A. lunulatum (s.s.) comprising the universally known triploid apomict, the diploid and tetraploid sexual from S. India and the diploid apomict from W. Himalayas and S. India. The other species, A. teestae Verma would comprise of the E. Himalayan diploid sexual and diploid apomict forms together with the tetraploid sexual. Chromosomal associations in the 16-spore mother-celled sporangia have been analysed and on this eviednce the origin of the two polyploid types in Adiantum lunulatum is discussed. It is argued that the diploid apomict A. lunulatum (sensu stricto) probably originated in a previously sexual taxon. Genetically speaking, the diploid apomict is AA', while the triploid is AA'B in constitution but still possessing approximately X pairs+X univalents.
Cytological investigations on 20 taxa belonging to 13 species of grasses have been carried out from the hills of Darjeeling (E. Himalayas). Three species, Colpodium nutans (n=7), Tripogon jacquemontii (n=10) and Phyllostachys kumasaca (2n=48) were investigated for the first time. A putative hybrid O. compositus×O. burmannii was discovered from the area. It showed highly aberrant meiosis. Agrostis stolonifera has been found to possess 3B-chromosomes.
A number of autotetraploids were produced experimentally with colchicine and the frequency of multivalent vs bivalent associations was studied in seven autotetraploid plants of F. vesca. There were interplant variation in the frequency of quadrivalents between the seven autotetraploids of F. vesca and a highly significant correlation between quadrivalent frequency and chiasma frequency. The higher frequency of quadrivalents in 4x F. nippinoca was associated with a higher chiasma frequency. The pollen fertility of the autotetraploids were not correlated with meiotic irregularities, and the variation in fertility is attributed to genetical factors. Autotetraploid F. nipponica was partially self-compatible while the corresponding diploid species was completely self-incompatible. This breakdown of the selfincompatible system in the autotetraploid due to interaction of self-incompatible alleles in the diploid pollen is in agreement with the suggestion that the incompatibility genes in Fragaria species act in the pollen gametophyte.
Two species of the family Cichlidae, Tilapia rendalli and Geophagus brasiliensis, live at the same ecological niche and are morphologically similar. Cytogenetic study showed a diploid complement of 44 chromosomes in the former and 48 in the latter, with the N.F. of 52 and 51, respectively. The findings suggest that they have the same origin and the difference in chromosome number may be due to chromosome rearrangements.
An additional fragment frequently appeared in the root tip cells from a polyhaploid clone of smooth bromegrass (Bromus inermis Leyss). Occasionally, two or three fragments could be observed. Comparison of karyotypes between ramets with and without a fragment revealed that the fragment may have originated from the satellite which was detached from one of the SAT-chromosomes. The division of the SAT-chromosomes was considerably delayed at anaphase in the unpretreated root tip from the ramet with the fragment. In most cases the lagged satellite eventually divided and incorporated into the daughter nuclei. However, in many divisions the separation of the daughter satellites was so much delayed that, as a result of the poleward movement, a break occurred between the daughter satellite and one of the parent chromosomes. The detached daughter satellite later became a fragment. Misdivision, lagging or nondisjunction of the daughter fragment could explain the different number of fragments in subsequent generations of cell divisions.
Gonial somatic and meiotic karyotypes of male diabetic and normal Mystromys albacaudatus both show acrocentric X and Y chromosomes paired in meiotic pro-phase end-to-end, short-arm-to-short-arm. We have not seen the long submeta-centric X of Taitz (1954) and Srivastava, et al. (1974) nor the submetacentric Y of Srivastava, et al. (1974). No differences in karyotypes of normal and diabetic animals have been seen. Pachytene chromosome length varies by a factor of 3.16 among four different preparation techniques. The sex vesicle in pachytene is attached to the eighth chromosome pair. Different stages of meiosis require slightly Different preparation techniques for best results.
Observations on the meiotic behaviour of the Arandas have confirmed cytologically the hybrid nature of the Arandas, intergeneric hybrids between the Arachnis and Vanda forms. It is evident that the parental species of the Arandas from two widely different genera with varied differences morphologically, are not too closely related. A general trend of poor homology of parental chromosomes, high frequency of occurrence of meiotic irregularities and increased sterility was observed in the Arandas investigated. Multiple spindles, though of low occurrence may cause polyspory and hereby result in inviable gametes with variable chromosome numbers. Polyploids arising from the Arandas could possibly occur through functional diploid gamets and diads which have been observed, though these are of low frequency. Meiotic analysis of some species/hybrids of the parental Arachnis and Vanda genera confirms the regular meiotic behaviour and higher fertility within each genus. It is suggested that if doubling the chromosome number in the Arandas through, for example, colchicine treatment, is found to restore their fertility, then this would be the line of research most desirable in advancing a breeding programme for these orchids.
B-chromosomes are reported in five species of Crotalaria, namely C. brownei, C. juncea, C. medicaginea, C. retusa and C. sericea. While B-chromosomes were found in root tip cells of all the five species, in pollen mother cells, these were found only in two of these five species, viz. C. brownei and C. retusa. These results have been discussed.
Karyokinesis is a continuous morphological change of one metabolic nucleus which becomes two independent daughter nuclei via karyokinetic stages. In fixation cytology including present electron microscope studies, this principle on concerning the morphological continuation of the dividing nucleus is ignored, especially in higher plants and animals, because of the common concept about the breakdown of the nuclear membrane before spindle formation. The nuclear membrane in metaphase and also in succeeding stages fulfills an important role as an intracellular biological membrane morphologically and physiologically. 1. Chromonemata in a metabolic nucleus develop into chromosomes by addition of a chromosome matrix, and by coiling. Simultaneously the nucleus increases its volume. On the contrary, the daughter chromosomes at both spindle poles in telophase, change into chromonemata by releasing their matrix and unravelling coiling. Thus the daughter nuclei are dehydrated in plant cells but very little dehydrated in animal cells. 2. The nuclear sap in a metabolic nucleus changes into the atractoplasm, spindle ground substance, by transforming nuclear sap globular proteins into fibrous ones which become arranged in parallel with each other under the influence of cell polarity and form a tactoid as a whole. Thus the spherical metabolic nucleus becomes a spindle-form karyokinetic nucleus, generally described as a metaphase spindle, which possesses the essential contour for setting up an energy source (ATP) at both spindle poles. This interpretation of the metaphase spindle formation is backed up by the appearance of spindle-shape birefringence in living cells under polarization microscope. 3. By the fibrillation of proteins which starts from both spindle poles toward the equator of nucleus, the scattered chromosomes in the periphery of late prophase nuclear cavity are brought into the equator and form a metaphase plate. 4. Different from protista, including fungi and algae, the nucleus in higher plants and animals increases its volume to accomodate enough space for metaphase plate formation in prometaphase, for poleward migration of chromosomes in anaphase and for accomplishment of independent daughter chromosome groups at both spindle poles in telophase. Simultaneously, the spindle membrane, by increasing its surface area becomes a strained state and fragile toward fixation (coagulation) shock and dehydration, when fixed by routine fixatives including electron microscopic techniques. Thus it happens that the misinterpretation of the breakdown of the nuclear membrane before spindle formation has been described as an orthodox explanation in cytology books. 6. The parallel arranged spindle back-ground fibrils lay a track to conduct the flow of kinetochore substance exuded from each kinetochore site of the chromosomes toward the spindle poles. This flow forms the spindle back-ground fibrils on the track into a bundle and also forms a kinetochore fiber between each kinetochore and its corresponding spindle pole. 7. By aid of chemical energy (ATP), each kinetochore fiber, when it arrived at each corresponding spindle pole, disintegrates from its terminal and becomes continuously short. Finally, each kinetochore accompanying chromosome arm(s) arrives at and occupies the spindle pole at the end of anaphase. 8. During the shortening of kinetochore fibers in anaphase, the disintegrated kinetochore fiber proteins become daughter nuclear sap proteins. On the other hand, the daughter nuclear membrane is reformed from the spindle membrane at each spindle pole by replicating its membranous structure at the molecular level and enveloping in it the daughter chromonemata, nuclear sap and the reappearing nucleoli at the end of telophase. 9. Further changes such as those of daughter chromosomes, their chromonematization by releasing of the chromosome matrix, unravelling of coils and by changes in hydration
This study describes the features of the preprophase bands of microtubules found in the subsidiary and guard mother cells prior to mitosis. In subsidiary mother cells the two bands occur in complementary locations along the walls immediately above and below the guard mother cell. The preprophase bands of the guard mother cell are seen along the walls that are shared with the subsidiary mother cells on either side of the guard mother cell. The preprophase bands occupy a considerable width laterally and the microtubules occur several deep in the band. These features, however, do not give a clue as to what precise role the bands play either in the asymmetrical division of the subsidiary mother cell or in the symmetrical division of the guard mother cell.
The ultrastructural damage to the spermatid organelles of Locusta migratoria was studied after one injection of 10 microliter isopropoxy phosphine at 5th instar stage. The effects were prevalent after three to four weeks. Vacuolation was observed in nuclei of early spermatids. Some nuclei of advanced spermatids had crinckled nuclear wall. Occasionally, the nebenkern and its derivatives showed vacuolation. The formation of supernumerary flagellar complexes also occurred in some spermatids. Sometimes, the flagellar filaments were disorganized. The results are more or less similar to those which followed x-ray irradiation and corpora allata implantation.
A triploid and a tetraploid plant were isolated from mutagen treated populations of HB3 (Tif23A×J104) and HB1 (Tif23A×Bi13B) hybrid pearl millet, respectively. The triploid plant regularly showed univalents (1 to 9 per cell) and trivalents (1 to 6 per cell) at MI. In the case of the tetraploid, only bivalents were observed which showed loose or tight secondary associations at MI; at AI bivalents separated as units (instead of chromosomes), while at AII chromosomes (instead of chromatids) moved to the opposite poles. Although the chromosome behaviour was quite regular, the plant was highly sterile (98%). It is suggested that gammarays had induced mutations in a number of genes, including those affecting pairing, concomitant to the indution of tetraploidy.
Karyotypes of four species of Amorphophallus indigenous to South India have been studied. The chromosome numbers observed are 2n=26 in A. hohenackeri, 2n=28 in A. campanulatus and A. dubius and 2n=39 in A. bulbifer. Meiosis is normal in A. campanulatus and 14 bivalents are observed at first metaphase. Since 8 out of 10 species so far studied have 2n=26 or 39, the original basic number of the genus appears to be 13 from which x=14 in two species may have been derived by aneuploid gain of a pair of chromosomes. A. hohenackeri has larger chromosomes and more symmetrical karyotype than the other species. The close phylogenetic relationship of A. campanulatus and A. dubius indicated by their morphological characters is further supported by the similarity exhibited by their karyotypes. In A. bulbifer (2n=3x=39) the chromosomes of the three genomes of the triploid cannot be matched into groups of three homologues. Karyotype analysis suggests either extensive chromosome repatterning or that A. bulbifer is an allotriploid with two genomes derived from one species and the other from a different species.
Experimental autotriploids in Verbena tenuisecta were selfed and crossed with diploid type (2n=10). The progeny yielded plants with chromosomes varying from 10 to 16. The different polysomics were analysed morphologically and cytologically. Some of triploids (3%times;=15) were morphologically distinctive and their karyotypic analysis showed that they had a constitution 3n=15+1-1, being tetrasomic and disomic for one chromosome each. The paper disenssis the nature and extent of transmission of extra chromosomes in different polysomics. Presence of extra sat chromosome induces larger flower size and profuse flowering where as absence in hypotriploid adversely effect plant habit and the flower size.
Karyological studies are made in three strains viz. N. P. 48, N. P. 54 and N. P. 63 of Lens culinaris var. Microsperma for the first time. The normal chromosomal counts in all these three strains as have been obtained in the present study are n=7 and 2n=14. Meiotic abnormalities were recorded for the first time in these strains when they were subjected to intense cold and low temperature. No specific morphological characters are found to be associated with above meiotic abnormalities in natural population of the three strains of Lens culinaris var. Microsperma.
In Job's tears (Coix lacryma-jobi L.) autotriploids (3n=30), hypo-triploids (3n=29) and hyper-triploids (3n=31) were produced by crossing diploids and colchicine induced autotetraploids. Trisomics (2n=21), double trisomics (2n=22) and multiple trisomics (2n=27) were obtained in the progenies of triploids. In none of the trisomics or double trisomics, the nucleolar chromosome was involved in trisomy. In each of the chromosome classes, meiotic behaviour, fertility and transmission of extra chromosomes to the progenies were studied. The average frequency of trivalents for a set of 3 chromosomes in triploids and aneuploids varied between 0.62 and 0.92, which is much higher compared to the average frequency of quadrivalents for a set of 4 chromosomes in the tetraploids (including hypo- and hyper-tetraploids) which varied between 0.49 and 0.58. These apparently indicate that the frequency of multivalents tends to decrease as the number of homologues of a chromosome in the complement increases. The average chiasma frequency per cell in triploid was significantly less than one-and-half times that in diploid. Although this depression in chiasmata in triploid is difficult to explain, some probable causes were mentioned. In general, aneuploids were lower in fertility compared to diploids, and both hypo- and hyper-triploids were less fertile than triploids. Transmission of extra chromosomes to the progenies occurred more frequently through the female gametes than male gametes.
During studies over genetic parameters of the local red onion bulbs, certain progenies of maternal half sib families segregated a few white bulbs. Some of these bulbs bred true to the white colour and though they were sexually normal and fertile, a few exhibited seed sterility. These steriles when cultured separately were found to be either translocation heterozygotes or desynaptic strains. In plants a single meiotic ring involving either a few or the entire zygotic chromosome complement is known. But the formation of regular independent rings, each composed of 4 chromosomes, and involving the whole zygotic complement is unknown so far. This has been found in some of these white Allium cepa strains and represents a new type of translocation system existent in the plant kingdom. Predominance of either rings or chains or their equal proportion was observed in the various clones, each configuration being specific and constant for each clone. The predominant occurrence of rings in certain clones could be because the sites of chromosomal breakages are closer to centromere and interchange pieces are more or less equal in length. But where the interstitial segment is short, exchanged pieces are relatively small thus resulting in chain configuration formations. Though pollen fertility ranged from 9-22 per cent, seed sterility was complete in these translocation heterozygotes. When the clones were selfed or intercrossed among each other or crossed as seed or pollen parent with normal fertile Allium cepa, no seeds were set, indicating thereby the existence of male and female sterility in these clones. Genetic control of these regular and specific translocations has been postulated. Since such a type of translocations involving regularly 2 heterozygotes, each of the entire genome, are extremely rare and occur in a very low frequency, their control seems under recessive genes.
A tertiary trisomic plant was obtained in the progeny of an interchange heterozygote T 2-6 in a 6-rowed barley variety K 12. It differed from normal diploids in morphological characteristics. Pollen and ovule fertility were greatly reduced. The extra chromosome showed different types of associations among which chain of five chromosomes was the most frequent configuration. Trivalents mostly oriented in V-shape while pentavalents oriented in zig-zag shape, both giving rise to alternate segregation. The greatest frequency of segregation at anaphase I was that of 8-7 type.
The structure of the ascus apex in Hypoxylon serpens (Pers. ex Fr.) Fr., Poronia punctata (L. ex Fr.) Fr., Rosellinia aquila (FR.) de Not., and R. mammiformis (Pers. ex Fr.) Ces. and de Not. is described. It is suggested that the apical apparatus has a much simpler construction than early light microscopy indicated. Micrographs show that the only differences are variations of a basic construction common to all.
The study pertains to the cytogenetics of a newly synthesised trispecific hybrid N. benthamiana (n=19)×N. glutinosa (n=12)×N. tabacum and its allopolyploids. The F1 (n=55) plants were phenotypically identical and by colchicine treatment 2 partial and 2 complete allopolyploids were obtained. The study show that it is not possible to maintain the stability in these allopolyploids, when chromosome number is increased beyond certain limit. However they are useful to understand certain fundamental aspects of evolution. Recently the trispecific hybrids have gained additional importance as they offer an excellent tool to combine two non-crossable species through a ‘bridge’, thus makeing it possible to transfer disease or pest resistance traits from wild species to the species of commerce, N. tabacum.
The karyotype of the red brocket deer, Mazama americana is described. Skin biopsies of a pair and their young male offspring were cultured for the study of centromeric heterochromatin and G-bands. The chromosome number of father and son was 2n=50; that of the doe was 2n=49 in all metaphases examined. In the doe, one of smallest acrocentric elements was missing and is apparently translocated to the end of the long arm of one submetacentric chromosome No. 4. This translocation of the non-Robertsonian type has not been described in Artiodactyla before, moreover, the chromosome number differs from that reported to be as 68 in one single specimen reported previously.
Paper deals with the cytological studies of Thevetia peruviana, Holarrhena antidysenterica, Carissa spinarum, C. bispinosa, C. carandas, Nerium indicum and Alstonia scholaris. Karyotypes of three varieties of T. peruviana were similar and all the chromosomes has sub-median constrictions. In H. antidysenterica one pair had median while the rest had sub-median constrictions. Meiosis in above mentioned diploid plants was fairly normal except for spindle anomalies in Nerium indicum and Carissa carandas. Artificially induced tetraploids of N. indicum show low multivalent frequency while they were absent in those of Thevetia peruviana.
When the eggs of the sea urchin, Hemicentrotus puicherrimus, were activated by 3 times' repetition of the insufficient treatment with butyric acid, DNA was synthesized in the nucleus at the adjacent region of the nuclear envelope and on the chromatin, even though cortical granules did not breakdown. In parallel with this, RNA and protein were also synthesized. In such an egg, several small aggregates of the chromatin are gradually formed in the nucleus and grow to the “nuclear dense body (NDB)” near the nuclear envelope. Formation of the NDB is suppressed with actinomycin D and cycloheximide in high concentration, and a matrix of the NDB is digested by the treatment with Pronase. From these results, it was supposed that accumulation of synthesized DNA, RNA and protein in a nucleus brings an increase of osmotic pressure or physical expansion within a nucleus and results in nuclear swelling.
The characteristics of granular haemocytes of four non-insect arthropods were compared. The refractile, bacilliform granular inclusions dissolve in aqueous solutions of dyes. On glass slides, the cytoplasm of the haemocyte becomes distinctly separated into agranular ectoplasm with well developed filopodia and granular endoplasm. The mode of formation of vacuolar droplets together with the association of granules with them suggests secretory activity of the haemocytes. Fragmentation of cytoplasm or clasmatosis is common feature of granular haemocytes from prechilled animals. The significance of clasmatosis is discussed. The present study indicates that the plasmatocytes reported by previous workers may be the altered granular haemocytes. The characteristics of granular haemocytes of arthropods are compared with that of the granulocytes of molluscs.
Mitosis was studied in the root-tip cells of Chionographis japonica Maxim. (2n=24; Liliaceae). Mitotic chromosomes of this species were found to show several unusual characteristics in the appearance and behavior; namely, the chromosomes at metaphase and anaphase do not show any distinct morphologically visible constriction, and the sister chromatids in mitotic anaphase separate quite in parallel. These characteristics are, apparently, quite different from the ordinary monocentric type of chromosomes. In order to make clear the motile system of the chromosomes, the X-ray irradiation experiments were carried out. Many fragments of chromosomes were produced by the irradiation. The ratio of the chromosome-aberrant cells fixed on 10th day after irradiation (Lot no., R-4) was 82.7%, and this ratio was almost as high as the ratio of the aberrant cells obtained in lst day collection (Lot no., R-1) after irradiation. In spite of these high occurrences of the aberrant cells, chromosome separation was quite normal in most of the anaphase and telophase cells examined, and no micronucleus was detected. In many anaphasic cells, minute fragments could be observed to separate quite normally, just like as the normal chromosomes. Therefore, most fragments of chromosomes could survive in the subsequent generations. All these observations seem to suggest that the chromosomes of Chionographis japonica are of the holocentric ones.
Chromosomes in the root-tip cells in four species and one variety belonging to the genus Polygonatum (Liliaceae) were treated according to the modified C-banding technique. As results, both the centromeric regions and the secondary constrictions of the satellite chromosomes in each species were found specifically deeply stained. In P. odoratum var. pluriflorum, besides these chromosomal regions, distal regions of several chromosomal arms were also stained deeply. The stained portion in the centromeric region of the chromosome is spherical in shape and has a diameter of 0.2-0.3μ, and is always seen at the apex of the chromosome flexure migrating toward the spindle pole at mitotic anaphase. The appearance and the behavior of this centromeric spherule were found quite compatible with some of the known characteristics of kinetochores. These stained kinetochores could also be seen in the interphase nuclei. They localize in a cluster at one side of the nucleus. The observations on the appearance and behavior of these stained kinetochores allowed us to suppose that chromosomes in interphase, prophase and late telophase are strongly polarized, and arranged keeping their anaphase-telophase orientation. As the kinetochores during these periods could always be seen in the periphery of the nucleus, adjacent to the nuclear membrane, they were considered to be attached to the inner layer of the nuclear membrane, and to act as the anchore sites to link the chromosomes. Thus the role of the kinetochores during these periods was emphasized. During interphase, initial single kinetochores were found to replicate and form the doubled ones. But these doubled kinetochores do not divide until the earliest prophase. Some of the doubled kinetochores seemed to fuse two by two to form larger spherules during the interphase. As the kinetochores could be stained after C-banding treatment, they were supposed, accordingly, to be constitutive heterochromatic regions in the present materials.