The effects of surface-active agents on mitosis was studied by applying 22 compounds, including representatives of the four major ionogenic classes, to a standardized pea root meristem test system. Mitosis was inhibited by 16 surfactants at 0.1% v/v; the ionogenic type appeared to be unimportant. Two surfactants caused a slight depression of the mitotic index; the remaining four had no recognizable effect. Ten surfactants (nonionic, anionic, and cationic) were toxic at 0.1% v/v. Of the six known biodegradable surfactants tested, five were toxic at 0.1% v/v.
Chiasma frequency at diakinesis was studied in eight inbred lines and three single crosses. In each case, comparison was made among three groups of anthers, classified according to the relative frequencies of division stages as follows: Group 1 with about 1:1 diakinesis: early stages, Group 2 with PMC's mostly in diakinesis, and Group 3 with about 1:1 diakinesis: late stages. In the inbreds chiasma frequency was highest in Group 1 anthers and lowest in Group 3 anthers. The reverse was true in the hybrids, as indicated by the average values. But considering the hybrids individually, one hybrid gave a picture similar to the inbreds and the remaining two showed the reverse trend. Two kinds of internal factors with opposing effects appear to determine chiasma frequency at diakinesis. One is temporal and tends to reduce the number by terminalization. The other is spatial and is due to the interaction of neighbouring meiocytes. While the first appears to be predominant in the inbreds, the second appears to be more conspicuous in some hybrids, tending to increase the incidence of chiasmata.
1. Chromosome numbers are listed for forty-nine species and varieties not previously studied cytologically. 2. Two of the species studied are polyploids and the others are diploids. 3. Chromosome numbers are listed for seven genera of which chromosome numbers have not previously been reported.
Tetraploid chromosome number of n=14 chromosomes has been counted in a few plants originating from 0.2 per cent colchicine treatment and in one plant originating from 0.4 per cent colchicine treatment while control plants have revealed n=7 chromosomes. Meiotic irregularities have been noted in the plants originating from colchicine treatment in contrast to regular meiotic divisions observed in the control plants. Number of stomates per field decreased with the increase in colchicine treatment and stomates and pollen grains of the biggest size were observed in plants originating from 0.4 percent colchicine treatment. Bifurcation of main stem and dwarf plant with deformed leaves were observed in a few plants originating from colchicine treatment. Factors responsible for the origin of morphological abnormal types and cytological mechanism responsible for the meiotic irregularities observed have been considered.
1. In malignant cells of primary tumor the predominant form of mitochondria is the filamentous one, while in cells of different metastases mitochondria exist in the form of granules. 2. In cells of primary tumor, besides the dictyosome-like form of Golgi apparatus which is found also in different metastatic cells, a second type of Golgi apparatus exists in the form of osmiophilic granules. 3. The degree of development of Golgi elements and the amount of mitochondrial granules vary with the organ localisation of metastases. 4. In cells of different metastases the elements of Golgi apparatus are well developed with an increase in the number of mitochondrial granules when compared with that found in cells of primary tumor. 5. In malignant cells of old primary and secondary tumors the Golgi elements are well developed along with an increase in the number of mitochondrial granules in comparison with that observed in cells of the homologous young tumors.
For the purpose to examine whether or not the DNA-like fibril is the com-ponent common to chloroplasts, the electron microscopic observations were made on the cells of several species belonging to Rhodophyta, Phaeophyta, Chlorophyl a, Charophyta, Bryophyta, Pteridophyta, Gymnospermae and Angiospermae with special reference to the “DNA fibril complexes” which appear as dense structures in the electron-transparent regions of the chloroplasts. As the result, it has been demonstrated that the DNA fibril complexes are observable in the chloroplasts of the cells of several plants belonging to Rhodophyta, Phaeophyta, Chlorophyta, Charophyta and Bryophyta, and in the young cells of several plants belonging to Pteridophyta, Gymnospermae and Angiospermae without any exception, indicating that the DNA fibril complex would be a component of the chloroplasts widely distributed in lower plants as well as in higher plants. In fully developed chloroplasts in older tissues of some vascular plants, namely, of Equiselum arzvense, Ginkgo biloba, Metasequoia glyfitostroboides, Spinacia oleracea and Zea mays, no DNA fibril complex is found in the electron-transparent regions. DNA fibril complexes appear as fibrous structures with cloudy aggregates and core-like structures. Some differences in the morphological appearance of the complexes have been observed according to different species.
For the purpose to clarify wether or not the “DNA-like fibril” is the common component of the mitochondria of plant cells, the author carried out observations on the cells of eighteen species of eight phyla by electron microscopy. As the result it was found that the DNA fibril complexes are located in the electron-transparent regions of mitochondria in the plants cells belonging to Rhodophyta. Phaeophyta, Chlorophyta, Charophyta, Bryophyta, Pteriodophyta, Gymnospermae and Angiospermae. These results suggest that the DNA fibril complex is the common component of mitochondria in plant cells as well as in animal cells. The morphologic patterns of the DNA fibril complexes of various species observed under electron microscope are similar in that they are composed of fibrillar elements whose unit fibrils are apparently about 3mμ in width. The dense aggregates and the core-like structures, frequently encountered in some species, are supposed to be dense distribution of fibrils, but there seems to be some specificity in the morphologic structure of the DNA fibril complex specific to each species.
For the purpose to detect the so-called DNA-like fibrils, “DNA fibril complexes”, in chloroplasts and mitochondria of the cells at several stages of the life cycle, the cells of endosperm, egg, proembryo, embryo, leaf and pollen of Ginkgo biloba, were examined by electron microscopy. As the result DNA fibril complexes have been found in both chloroplasts and mitochondria of the cells at all the stages of the life cycle as far as the present observations are concerned without any exception. Therefore, it is suggested that the DNA fibril complex persists in every stages throughout the life cycle of plant.
Two cultivars belonging to A. cepa var. viviparum are cultivated in India. One of these is a diploid (2n=16) and is karyotypically heterozygous. The other is a triploid and contains a diploid and a halploid set (AA B) in its karyotype. Both cultivars have only one chromosome with a satellite in their somatic complements. The triploid is extensively cultivated in Kashmir.
Fertilized eggs of Fucus evanescens were cultured with actinomycin D, chloramphenicol, uracil, and 2-thiouracil. As a result, the following was obtained. 1. Differentiation of the rhizoid protuberance and its primary elongation are inhibited by actinomycin D and also by chloramphenicol, and are accelerated by uracil. 2-thiouracil does not affect the both. 2. Further elongation is also inhibited by actinomycin D and by cholramphenicol, and is accelerated by uracil. A striking feature at this stage is that the rhizoid is ramified dichotomously by 2-thiouracil. 3. It seems that successive synthesis of messenger RNA and protein is necessary for differentiation and subsequent elongation of the rhzioid, and each stage is mediated by different messengers and proteins. So that, the development ceases if the new synthesis is blocked by actinomycin D or by chloramphenicol, and the effect of 2-thiouracil occurs only in the secondary stage of elongation.
The paper presents the investigation of nondividing PMC's in the sporogenous tissue of Allium tuberosum and Allium cepa. The nuclei in such PMCs do not undergo division at all while the normal cells regularly divide. Studies of stigma squashes also revealed similar nuclear condition in pollen produced by the nondividing PMC's. Though no division takes place in such cells, yet, they are transformed into pollen grains along with the normal cells. Certain workers have reported partial suppression of meiosis during gametogenesis but this is the first record of complete suppression of nuclear division. It is suggested that nuclear division and transformation of the sporogenous cells into PMC, sporads and finally pollen are independent processes. The possible explanations of this peculiar behaviour of the nuclei of these cells is also suggested.
Dry dormant seeds of Phalaris canariensis Linn. (2n=12) and Phalayis minor Retz. (2n=28) were irradiated with 10 Kr. soft X-rays at the M.R.C. Unit, Hammersmith Hosptial, London and its effect on the production of chlorophyll, and morphological mutants at M2 generation have been studied and discussed in both the species. In Phalaris canariensis Linn., the usual chlorophyll mutants, virescens, chlorina, lutescens, albino, tigrina, virido-albino and maculata were seen at seedling stage. Viridis was found to be most common and maculata to be rare. When viridis was broken up into different types on the basis of colouration, lutescens is commoner than virescens and chlorina which are present in almost equal numbers. The frequency of mutants varies from 0.22-4.5. This was determined per 100 M2 seedlings (Gaul 1960) and was found to be higher at the low fertility range. No mutants were seen between the 71 and 90% fertility classes. Morphological mutants of the type, split and appendage on the margin of the leaf, split on the margin and lamina, appendage on the margin, trifid and bifid apex, rudimentary leaf, leafless, twisted and pendulate rachis and whitehead, tweaky, multiflorous, impeded, white-green and spikeless infloresence have been observed in P. canayiensis. No chlorophyll and morphological mutants were seen in P. minor inspite of 19, 708 seedlings tested. The appearance of chlorophyll and morphological mutants at M2 generation in the diploid species P. canariensis (2n=12) suggest that they are more sensitive to radiation than the tetraploid P. minor (2n=28).
1. Spermiogenesis was studied in living and fixed cells from pupal and young adult testes of Aedes aegyvti (L.). 2. Fusion of thickened, rod-like mitochondria in cytokinesis of the second meiotic division results in nebenkern formation. Very early in spermiogenesis an axial filament makes its appearance, extending from the nuclear membrane to bisect the nebenkern. In the course of differentiation the axial filament and nebenkern extend distally from the nucleus to result in flagellum formation. 3. Condensation and elongation describe nuclear differentiation. Midway in spermiogenesis two juxtanuclear bodies of uncertain origin become strikingly apparent in the head piece but are lost to view in final maturation. 4. No dictyosomes, acroblast or acrosome were observed. Further, germ cells were periodic acid-Schiff negative. Thus no acrosome develops in spermiogenesis. 5. The fully differentiated spermatozoon is a thread-like cell consisting of (a) a needle-like nucleus and (b) a flagellum of two mitochondrial threads and a central axial filament.
1. Localization of some phosphatase activities was investigated in the cells cultivated in the multipurpose culture chambers developed by Rose. 2. The activity of thiamine pyrophosphatase was specifically confined to the surface of the phase-gray flecks in the Golgi region. The reaction products encrusted the phase-gray flecks and formed what looked like a tubule with chromophilic walls and a chromophobic lumen, which was similar to a Golgi body demonstrated by metallic impregnation in vertebrate somatic cells. 3. Based on theevidences obtained in the study, it was justified that the phase-gray flecks were the true representatives of the Golgi apparatus in the living cultivated cells and supposedly correspond to the double membrane systems of the Golgi complex observed under the electron microscope. 4. The activity of the acid phosphatase was also found to be associated with the phase-gray flecks, but not with the phase-white vacuoles in the Golgi region which were presumably considered to be lysosomes or secretory droplets. 5. In many preparations showing thiamine pyrophosphatase and acid phosphatase activities, while deposits of the reaction products were found in a very small quantity on the phase-gray flecks in the more central porition of the Golgi region, they were concentrated in a greater quantity on the more peripherally located flecks in the same region. No significant staining was obtained in the test for alkaline phosphatase.
Cytological studies of four species of Coleus indigenous to South India have been made. They are C. malabaricus (2n=28), C. spicatus (2n=30), C. amboinicus (2n=34) and C. payvifloyus (2n=68). The chromosomes are small in all these species. Meiosis is regular in C. malabaricus, C. spicatus and C. amboinicus. It is very irregular in the cultivated species, C. payviflorus, forming varying numbers of quadrivalents, trivalents, bivalents and univalents. The species is possibly an autotetraploid. The chromosome numbers of eleven species known in the genus (n=6, 8, 14, 15, 16, 17 and 24) indicate that a still larger diversity in basic numbers, as reported in some other genera of the Labiateae, can be expected in Coleus also. Aneuploidy and amphidiploidy appear to have played important roles in the evolution of the genus.
The history of the nucleus and its method of division during ontogeny have been studied in Chara contraria and C. zeylanica. The results indicate that amitoses in the internodal cells of Chara are not manifestations of degeneration but, on the contrary, that they follow an orderly sequence. Amitosis involves a change in the form of the nucleus of the internodal initial to a ring-like one and division of the ring into two crescentic portions. A similar pattern of amitosis is repeated until, in older internodal cells, the minute, crescentic nuclei appear in clusters, often in denser masses of cytoplasm.
Persisting nucleoli were found in the fern, Ophioglossum petiolatum Hook. The nucleoli remain attached to the chromosomes until meta-anaphase at which time they are extruded from the spindle and are displaced poleward to become situated in the peripheral cytoplasm. They may persist through interphase and into the next mitosis. The nucleoli undergo structural changes during mitosis. They apparently lose the dense granular components present in interphase nucleoli and appear as loosely organized fibrous masses. A tripolar spindle was observed in which the spindle appeared to be slightly twisted. The high chromosome number (2n≈1020) facilitated the study of the centromere region, although no fine structural differentiation of this structure was found. Spindle fibers do not converge on highly localized poles but tend to become disorganized in the polar regions. The presence of undulations and sinuses along the length of the chromosomes suggests. coiling of the chromosomes and a subchromatid structure.
Cytological observations on 40 taxa of South Indian ferns belonging to 32 species were made. Eighteen of these are diploids and the others show various levels of polyploidy (triploid to octoploid). Haploid chromosome numbers like n=30, n=38, and n=36 were observed in Pellaea boivini, Ceratopteris thalictroides and Grammitis attenuata respectively, which are new reports for these three genera. Evidences of new basic numbers like x=43 and x=30 were also obtained in the genera Lindsaya (L. heterophylla, n=86) and Doodia (D. media, n=60, 2n=120) respectively. The occurrence of more than one cytotype has been demonstrated in Pteris ensiformis v. victoriae, P. pellucida, Ceratopteris thalictroides, Asplenium unilaterale and Microsorittm pteropus. Irregular meiotic behaviour suggestive of hybrid origin has been studied in Pteris ensiformis, Microsorium pteropus and Salvinia auriculata. Adiantum polyphyllum was found to be a sterile hybrid.
1. Distinct polyploidy is found in four forms of freswhater C. glomerata. Its forms constitute a polyploid series based on the chromosome number of 12; which are shown as follows: C. glomeyata (L.) Kütz. is octaploid, 8n=96. C. glomeyata forma genuina is hexaploid, 6n=72. C. glomerata forma Callicoma is tetraploid, 4n=48. C. glomerata subforma Kiitzingiana is tetraploid, 4n=48. 2. The chromosome counts reported by Geitler (1936) in a form of C. glomeyata, and by Schüssnig (1954) in another form of C. glomerata are confirmed. 3. The size of polyploid nuclei is larger than the haploid and diploid ones, and the maximum number of nucleoli varies directly with the degree of polyploidy. 4. A correlation between the number of chromocentre-like bodies, and the number of nucleoli has been observed and an association between these two structures is particularly observed in forms of C. glomeyata. The chromocentre-like body may therefore represents a nucleolar organising region of a chromosome. 5. Polyploidy is found only in freshwater species; the marine species being diploid (Sinha, 1963 and 1965). 6. The detailed morphological characters of four forms of C. glomeyata have been studied. Photomicrographs have been produced in support of the evidence of the presence of nucleoli, associations of chromocentre-like bodies with nucleoli and the mitotic chromosome counts. The method of staining by acetocarmine has been used for cytological study.
The survival pattern of fern protonemata resulting from UV-exposure is controlled by post-illumination of visible light. A favourable effect of blue light on the survival of Pteris vittata irradiated by UV was demonstrated.
1. The present studies deal with the histochernical observation on nucleolus and its extrusions in the egg-follicle of five dipteran species, viz., Dyosophila melanogaster, Musca domestica, Dacus cucuybitae, Psychoda bengalensis and Culex fatigans. 2. The trophocyte and oocyte nucleolus consists of RNA, proteins and bound lipids, except in Dyosophila and Musca; in these species the oocyte nucleolus does not possess RNA. 3. DNA appears in the oocyte nucleolus during the growth period in all the five species. 4. The nucleolus buds off granules rich in ribonucleoporteins and bound lipids; these granules migrate into the ooplasm. 5. The mode of emission of the nucleolar material and their role in proteid yolk synthesis have been discussed.
Pachytene pairing and meiosis in the F1 hybrid of P. typhoides and P. purpureum has been worked out. On the basis of the diagnostic characters of the pachytene chromosomes of the two parents the chromosomes forming pairs in the hybrid were made out. The first five chromosomes of typhoides are homologous with the first five chromosomes of purpureum. The sixth and seventh chromosomes of typhoides are homologous with the eighth and fourteenth of purpureum respectively. Autosyndetic pairing of chromosomes of the “B” genome of purpureum which is in a monoploid condition was observed; this pairing is non-homologous and not associa-ted with chiasma formation. The chiasma frequency in the F1 hybrid is lower than either parent and at metaphase I ring bivalents are never more than two per cell, all the others rod bivalents. There is irregular distribution of chromosomes at anaphase I and II. Laggards and micronuclei were observed.
1. In the present investigation the karyotypes of H. gracilis (2n=4) and those of H. ravenii (2n=8) were comparatively studied. 2. Chromosome 1g, the long V-shaped chromosome of H. gracilis, possessed three heterochromatic regions which indicate that this chromosome is composed of three chromosomes 1r, 2r and 3r of H. ravenii arranged in tandem order, 1r-3r-2r. Both the elimination of the centromeres from chromosomes 2r and 3r and the loss of a long euchromatic segment in the long arm of chromosome 2r might have played a role for the organization of chromosome 1g. 3. Chromosome 2g, the satellite Js-shaped chromosome of H. bracilis, was presumed to compose of both chromosome 4r, the satellite js-shaped chromosome of H. ravenii, and an euchromatic segment translocated from chromosome 2r.
1. A karyological study was made on Narcissus jonquilla. The chromosome number of the twenty clones collected from five different gardens were found to be 2n=14. 2. All clones studied showed similar karyotype, i.e., the chromosomes can be grouped into seven pairs. 3. The heterochromatin located in the distal end of the short arm of the shortest pair of chromosomes shows negative heteropycnosis. It has been observed for the first time that the heterochromatin forms a nucleolinus within the nucleolus during prometaphase and resting stage.
1. F1 hybrids between Secale anatolicum and six other rye “species” are heterozygous for two interchanges. Chains and rings of six at metaphase of meiosis in the hybrids show that the two interchanges involved three chromosomes. 2. Relative frequencies of chains or rings of IV, V and VI vary between different F1 genotypes. This variation is correlated with genotypically controlled variation in PMC chiasma frequencies between hybrid genotypes. The lower the chiasma frequency the higher the frequencies of IVs and vice versa. 3. The frequency of disjunctional arrangements, i.e. where alternate celitromeres move to opposite poles, are highest for associations of IV, least for VIs. From this it follows that the genotypes showing the highest overall disjunction per PMC are those with most IVs-namely those with low chiasma frequencies (see 2 above). 4. The degree of disjunction of associations of the same length does not vary between genotypes. 5. The disjunction frequencies in all associations, IVs, Vs and VIs, are very much higher than would be expected on the basis of a random orientation of centromeres.
The organization and fine structure of chromosomes and nucleoli of Euglena gracilis were investigated following the selective inhibition of synthesis of RNA by actinomycin D. The features of the morphological changes induced greatly depended upon the stage of the cell cycle in progress during exposure to the antibiotic. Actinomycin D lacked degradative effect on preformed nucleolar material and intra or extranucleolar chromatin but effectively cancelled out deposition of nucleolar material and chromosomal matrix. In the actinomycin-treated cells of Euglena the integrity of nucleoli was undisturbed even throughout experimental conditions which led to extreme depletion of nucleolar material.