Five horticultural forms of Carica papaya growing in India have been studied. Karyotypes of them represent homogeneity. Slight structural difference in chromosomes of different varieties is noticed, which proves the role of structural alteration of chromosomes on the evolution of the forms. No heteromorphic pair, or unpaired chromosome or any chromatin body, suggesting chromosomal basis of sex difference in the species, could be recognized.
A morphological study was made of membrane configurations in Penicillium viridicatum Westling and Trichothecium roseum Link, both members of the Fungi imperfecti. These membrane configurations (similar to previously described “myelin figures” and “mesosomes”) were observed after glutaraldehyde fixation and osmium tetroxide postfixation, but not after potassium permanganate fixation. Configurations with lamellar membranes occur in both P. viridicatum and T. roseum. In P. viridicatum, these configurations were found in the cytoplasm and in vacuoles, while in T. roseum they were found between the cell wall and plasmalemma and in the cytoplasm. Configurations with tubular elements were found in the cytoplasm of T. roseum, often in close association with the plasmalemma; and in vacuoles. These configurations appear to originate in the cytoplasm or between the plasmalemma and cell wall, and are later enclosed in the vacuoles, either in the living fungus or during preparation for electron microscopy.
Supernumerary division following telophase II in spore mother cells of a tetraploid Rumohra aristata (2n=164) has been studied in detail. This division was found to occur either in the four nuclei resulting at the end of telophase II or in the tetrads formed from normal meiotic division. Nuclear material did not show any evidence of duplication. Each spore mother cell at the end of supernumerary division gave rise to eight aberrant sterile spores. Rarely some spore mother cells showed normal meiosis resulting in the formation of four normal spores. Spore sterility has been estimated to be 98%.
Cytological studies have been made of South Indian grasses with a view to re-examine the taxonomic status and inter-relationships of the various tribes and genera making use of the additional evidence from cytology. The present paper deals with the cytology of 24 species representing 16 genera. Of these, the cytology of 14 species has been studied for the first time. The chromosomes of most of the species are very small, ranging in length between 1μ and 2.5μ. As reported by previous workers, the basic chromosome number of the grasses ranges from 5 to 12. Chromosome number in multiples of 8 which has been reported to be a rare occurrence in the grass family has been encountered in two species, viz. Arundinella setosa (n=8) and A. mesophylla (2n=16). The presence of high polyploid and aneuploid chromosome numbers shows the role of polyploidy in the evolution of the bamboos. The Bambuseae, Oryzeae and the Arundineae are closely related as they have high polyploid numbers in multiples of 12. The Aristideae is a highly advanced tribe, probably derived from the Arundineae. The Centotheceae is closely related to the Oryzeae as suggested by de Wet (1960). The present cytological evidence shows that Thysanolaena is related to the Arundineae. The present study has confirmed the systematic position assigned to the Arundinelleae by Stebbins and Crampton (1961). The Festuceae and the Aveneae which are closely related morphologically, have large chromosomes with the dominant basic number 7.
Only cells with the full complement (2n=33) selected in the germ line during male meiosis. The average association of chromosomes at metaphase I is 0.46III+10.5II+10.6I per cell. The most common association is 11II+11I. Anaphases show irregular segregation, bridges with and without fragments, laggards, precocious division and misdivision. Pollen fertility is hardly 1%. Micropollen grains formed from the lagging univalents contained only one chromosome of the short category. The taxon is totally seed sterile but is perpetuated by vegetative reproduction. From the heteromorphicity of the longest triplet and the presence of only one nucleolar chromosome, it appears that the taxon is allo- or segmental allo-triploid which is supported by the presence of 11II+11I during meiosis.
The chromosome numbers of 34 species representing 11 of Schlechter's sections were determined, of which 32 were 2n=38 and 2 were 2n=40. The chromosome numbers of 7 of these species had not been reported previously. Detailed examinations of chromosome morphology were made of species representing 11 sections. The mean chromosome size, S%, and F% were as variable among species within a section as between the sections. Although karyotype analysis of species did not prove to be useful in delineating sections in the genus Dendrobium, it was utilized in an attempt to clarify the taxonomic relationships between D. biggibum and D. phalaenopsis.
In a series of 19 postmortem short term blood cultures for chromosome analysis, 3 cases unexpectedly showed fibroblasts. These blood samples were obtained by puncture of the right atrium of the heart. Fibroblasts apparently originated from fragments of tissue inadvertently introduced into the culture. To substantiate this, 20 random punctures of the atrium of the heart at autopsy were done and 3 samples contained tissue fragments in the cell blocks. The incidence of fibroblasts growing out of cultures are quite similar. Therefore this supports our view that fibroblasts originate from tissue fragments rather than from a transformation of leucocytes into fibroblasts.
Chromosome studies were done on a total of 19 post mortem blood samples in order to determine how suitable post mortem blood would be for this purpose. Chromosome analysis can be successfully carried out if the sample of blood is taken less than 24 hours after death and sample has nearly normal hemoglobin and hematocrit values. However, it is more important that the sample should have a sufficient number of lymphocytes. This is generally found in blood samples with higher white counts. The perinatal group had 42% successful cultures whereas the adult group had 33%. This may be due to relatively high white count and higher lymphocyte count in perinatal cases. Incidentally, there were three cultures which showed a fibroblast-like cell growth in 72 hours.
Different samples of two species of annual chrysanthemum-C. carinatum and C. coronarium were analysed cytologically. These two species were found to maintain a significant amount of interchange heterozygosity. Presence of heterozygosity in C. coronarium has been observed for the first time and the variation in the size of multiples from the earlier studies on C. carinatum was also observed. This difference is concluded to be due to the difference in climatic factor.
The diploid number of chromosomes of Macrobrachium siwalikensis, Paratelphusa (Barytelphusa) masoniana, and Potamon (Potamon) koolooense is 100, 134, and 80, respectively. All the chromosomes in M. siwalikensis are metacentric, but in the remaining two species the centromere location could not be determined due to their small size. No morphologically distinguishable sex-chromosomes have been observed in any of the species studied.
The membranous structures found in basidiospore-germ tubus of Volvariella volvacea consist of three main types of configurations: polyvesicular, myelinlike and multitubular. More complex and mixed ones were also observed. The formation of these structures seems to be initiated by aggregation and convolution of endoplasmic reticulum in the cytoplasm. They were found either free in the cytoplasm or associated with plasma membranes against the walls. The structures were also observed within vacuoles and storage bodies. Since the structures are widely distributed in the cells and are greatly varied in form and in size, they may play different roles of physiological function according to their developmental stages and their localities. The relationship among the complex membranous structures is also discussed.
A progeny of 210 plants raised from the selfed seeds of a raw allopolyploid (2n=42) of the parentage, Pennisetum typhoides (2n=14)×P. purpureum (2n=28) was analysed for variation. The method of metroglyph analysis was used. Segregants showing transgression in certain attributes over the values for the parental species were observed in the progeny as a consequence of genic segregation arising from the heterogenetic association of chromosomes of the constituent genomes. Inspite of fairly high degree of recombination, the population in general showed skewedness in distribution towards P. purpureum. There is a dominant bias for few attributes contributed by P. purpureum, while intermediate expression was observed for many others. The recombinants resembling amphiploid and P. purpureum occurred frequently. A cytological study of the progenies having pollen fertility ranging from 0 to 84 per cent has been made. The frequency of meiotic disturbances did not correspond to the extent of pollen sterility. The wide range of variation for pollen fertility in the progenies inspite of the meiotic stability and chromosome constancy points to the operation of genic factors controlling fertility. The role of cryptic structural hybridity in restoring recombinations and also in influencing the fertility-sterility status of the progenies has also been considered. The high meiotic stability of the progeny of the raw allopolyploid coupled with the facility for genic segregation is a welcome situation in the use of the hexaploids in back crossing programmes for improvement of the cultivated species.
Premeiotic and somatic interphase cells from inbred KYS of maize were scored for number of nucleoli. Dual nucleoli occurred in 32 of 508 cells in the meristematic region of root tips, but only one of 520 cells at premeiotic interphase had two nucleoli. All other cells had a single nucleolus. The occurrence of cells with two large nucleoli filling most of the nuclear space and cells with nucleoli at opposite nuclear boundaries disclosed that dual nucleoli were the result of widespread separation of organizers rather than inhibition of fusion due to a paucity of nucleolar material. A single nucleolus was attributed to proximity of organizers and nucleolar fusion. The presence of a single nucleolus in all but one exceptional cell at premeiotic interphase suggests convergence, preparatory to synapsis, of the two homologues of chromosome 6 during the mitosis preceding meiosis.
A primary trisomic was isolated in M3 from a population of thermal neutron irradiated 6-rowed cultivated barley K 12. Karyotypic study has revealed that the extrachromosome is chromosome 4. The present trisomic for chromosome 4 is morphologically distinct from the trisomic for the same chromosome in 2-rowed wild and cultivated barley described by Tsuchiya.
The meristematic cell flow or percentage of cells formed per unit of time is constant under standard experimental conditions. In this paper, the cell flow is measured directly under the action of the colchicine, by observing the cell increase at metaphase, and with the caffeine by observing the production and increase of binucleate cells in successive units of time. The analysis of different concentrations and periods of treatment has shown the 2hr treatment of 0.05% colchicine and the 4hr treatment of 0.1% caffeine as the more effective in order to measure the cellular increase. Both drugs have a depressive effect upon the division cycle as a whole, in a uniform and homogeneous fashion. Colchicine slows down the division cycle in a 50% and caffeine in a 60% of the normal cell flow. This depressing effect must be borne in mind in any estimate of the cycle time and mitotic rate by means of these drugs.
A crushed (semi-circular) tannin vacuole is observable in the motor cell of the Mimosa main pulvinus immediately after stimulation. If the motor cell is then soaked in tap water for 15 to 20 minutes, the tannin vacuole begins to take a spherical shape. Before stimulation, using anesthetized material, spherical tannin vacuoles are observable. In the presence of 0.01 M EDTA, the recovery of the tannin vacuole is accompanied by an increase in volume and surface area. But in the presence of CaCl2, the recovery process of the tannin vacuole scarcely is accompanied by changes in its volume and surface area. In the medium containing CaCl2 the recovery to a spherical shape is made by 15 to 25 minutes, while in the medium containing KCl it takes 30 to 40 minutes.
Meiotic behaviour of two partially desynaptic plants of Pennisetum ramosum (Hochst.) Schweinf., a diploid grass with 2n=10 chromosomes, is described. The normally paired chromosomes tended to fall apart at diplotene and post-diplotene stages, so that at metaphase I of several cells (Table 1) the chromosomes looked somewhat disorganized. The disjunctional stages were quite irregular. Different factors-extrinsic as well as intrinsic-which may have led to these meiotic abormalities are discussed.
Cytological abnormalities were caused in V. faba by the treatment with leaf extracts of two Lathyrus varieties, viz., L. sativus var. Local and PLK-65. The highest frequency of aberrations was observed in 0.5% of 72 hours soaking period of L. sativus var. PLK-65 leaf extract. So among these two varieties L. sativus var. Local contains less neurotoxic material and hence less effect. Hence this variety may be preferred for consumption over the other. However, it is better if one can breed for Lathyrus varieties devoid of lathyrogens. Since these lathyrogens are causing meiotic abnormalities, it is worthwhile to study whether there is any affect on the gonads in animals and further studies in hereditary aspects.
Distinct karyotypic differences between species of Cornus were not detected during a study of mitosis in root tip cells. C. Nuttalli was found to have 2n=22. Several interesting cytological abnormalities during microsporogenesis were evident in five species. A B chromosome was observed in several cells of C. rugosa during first division but not in second division. Globules persisted in some diakinesis cells of most Cornus species and could often be confused with chromosomes. Weak asynapsis was evident in several species. C. altornifolia, C. rugosa and C. stolonifera exhibited polyspory at the quartet stage. The result of these anomalies appears to be the generation of variability within the genus.