Three loci transcribing 5S RNA have been verified on the short arm of chromosome III of G. barbipes. Evidence is also presented which indicates that a fourth site may arise on this same arm by chromosomal inversion following a break within the major 5S locus. Autoradiography after 3H-uridine incorporation indicates that the major 5S locus on chromosome III is relatively inactive in transcription in nuclei of salivary gland cells while the minor sites actively transcribe 5S RNA.
Cells of the green alga Chlamydomonas reinhardiobserved in successive stages of cytokinesis contain numerous dilated Golgi vesicles near the cleavage plane and the site of new cell membrane deposition. They are located near the basal body region, and in a perinuclear orientation, often in close association with enlarged nuclear pores. The Golgi components are permanent organelles during cytokinesis; their position and arrangement in the cytoplasm does not appear to be random. Their relationship to cleavage furrow orientation and formation is discussed. The contractile vacuole of interphase cells is illustrated in micrographs and discussed with respect to diastole and systole. Based on ultrastructural observations and electron microscopic autoradiographs, a functional relationship between the Golgi apparatus the contractile vacuole and cell wall elements is proposed.
IRRI Accession 101508 of the wild species Oryza nivara Sharma et Shastry was crossed directly and reciprocally to six varieties of the cultivated species, O. sativa L. This accession was cross-compatible with the six O. sativa cultivars. Each of the parents and hybrids have median, submedian, and subtelocentric chromosomes. A combination of three median (chromosome number 2, 3 and 7), seven submedian (number 1, 4, 5, 8, 9, 11 and 12), and two subtelocentric chromosomes (number 6 and 10) were the most common set. The parents and hybrids differed markedly in their chromomeric pattern, chromatin length, and arm ratio. The most frequent chromosomal aberrations observed were loose pairing at pachytene, univalents, and quadrivalents at diakinesis and metaphase I, bridges and late disjunction at anaphase I, and bridges and laggards at telophase I. Based at pollen and spikelet counts, only O. nivara, O. nivara×TNl and O. nivara×Dgwg were partially sterile. The other F1 hybrids were fertile. The difference between the pollen and spikelet sterilities in most hybrids and parents may be due to environmental effects. There was no direct relationship between the meiotic aberrations observed and the sterility of the F1 plants. Chromosome pairing was essentially normal in all F1 plants and most of them are fertile, indicating that the O. nivara accession and the O. saliva cultivars have the same genome composition (AA). There is close affinity between IRRI Acc. 101508 and the O. sativa cultivars.
The present investigations deal with the mapping of the salivary gland chromosomes of the common house fly, Musca domestica (Muscidae: Diptera). Cytological map for five pairs of long, synapsed, polytene chromosomes has been constructed and a detailed description is presented for each chromosomal arm. They have been designated and classified purely in an arbitrarily fashion. The chromosomal complement of Musca domestica has been divided into 43 zones. A definite chromocentre is absent. Each chromosome has a separate centromere which serves as a marker to separate its right and left arms. The pair I constituted by the sex chromosomes has not been observed. They may be largely inert.
Karyotypic analysis of thirty two varieties of Phaseolus mungo L. showed reasonable differences between the varieties on chromosome length, position of primary constriction and in TF%. Two pairs of chromosomes were secondarily constricted with subterminal primary constriction and occupy first and second positions in the somatic complement in almost all the varieties. In the rest of the chromosomes, the majority showed submedian primary constriction and few showed median constriction. An average karyotype of Phaseolus mungo L. has been suggested basing on the results included herewith and also considering the previous reports on this line. The observation of TF% ranging from 24.31 to 27.82 revealed a symmetrical karyotypes for nineteen varieties. The rest were observed to be asymmetrical with TF% ranging from 28 to 38.23. The importance of karyotypic differences in evolution of varieties within a species has been discussed.
Pachytene chromosome morphology of Physalis angulata L. (2n=48) was studied. The 24 chromosomes were identified individually. Their diagnostic features and an idigoram constructed on the basis of total chromosome length, length of chromatic and achromatic segments and arm ratios are provided. Chromosome 15 is the nucleolus organiser. The twenty four bivalents reflect the occurrence of 2 genomes of twelve bivalents each. Considerable morphological similarities exist between the two genomes.
The somatic chromosome number in Solanum viarum Dunal syn. S. khasi anum var. chatterjeeanum Sengupta is 24, however, about 20.64% of plants are either with one or two B-chromosomes. The seeds of normal plant (2n=24) were treated with gamma rays and plants from R2 generation were selected for the study of effect of fragments on the flowering and pollen fertility and the probable origin of B-chromosomes. The change in the behaviour from self-incompatibility to self-compatibility along with variability in the flowering period, due to fragment bearing S-genes, induces higher adaptability in this plant to cope with changing ecological conditions. Increasing breakability and heterochromatization pave the way for S-gene-bearing fragments to reach the status of neutral and dispensable B-chromosomes.
The somatic chromosomes studied in the root tips of thirteen varieties of C. cajan revealed that all the varieties had the same chromosome number (2n=22) but there is much variation in their chromosome morphology. The total chromatin length was maximum (51.2μ) in variety NP 41 and its minimum value was noted in variety Ranchi. When the individual chromosomes were taken into account the shortest (1.0μ) and the largest (3.0μ) chromosomes were recorded in var. Ranchi and var. PT 301 respectively. The TF percent was maximum in variety Mothihari (45.05) and minimum in variety PT 301. The SAT chromosomes were noted in varieties T1, No 148 and NP 80. On the basis of D2 values the varieties were classified into seven distinct groups. (A-varieties PT 301; ILRI and 7S; B-T1 and C11; C-NP 39 and NP 80; D-Ranchi; E-NP 41, Motihari and BR 60; F-No 148 and G-Assam). This indicates that the variety formation in C. cajan had taken place mainly due to the change in the chromosome morphology and nature of genes.
Proplastids and plastids in meristem cells of the shoot apex from Nicotiana clevelandii×N. glutinosa were found to contain electron-dense inclusions as observed by means of transmission electron microscopy. Due to their higher electron-density they can be detected in glutaraldehyde-fixed but unstained material. Application of the method of elementary analysis by means of X-ray microanalysis (EDAX) showed the presence of both phosphorus and iron in these stroma inclusions. The formation of these inclusions is discussed in relation to plastid and cell development.
Twenty nine species belonging to nineteen genera included in the tribe Andropogoneae (Gramineae) were studied morphologically and cytologically. Out of these 7 species were diploid and 22 polyploid, Nine species were studied cytologically for the first time and twelve species were found to have both diploid and polyploid plants occurring in the same general area indicating origin of polyploidy in the recent past. In some species polyploidy was associated with hybridization, apomixis or both.
The cytological effects of water extract from Pulicaria cispa were studied with reference to Allium cepa. Two types of treatments were carried out, direct and recovery treatments. The concentrations used were 3, 5, 7, and 10%. The extract affected the mitotic index and the percentage of the mitotic phases in the treated roots. The percentage of anomalies increase with increase of concentration and duration of treatment. The occurred abnormalities were, spindle disturbance, stickiness and sticky bridges, and laggards.
Stem fragments of Passiflora quadranguaris were cultured in solid media at 28°C in the dark. We have obtained white and friable callus. The cytologic study reveales the existence of small meristematic centers which differenciate into parenchymatous cells and some tracheids. At the begining of the transformation of the meristematic cells into tracheids, the Golgi apparatus omits very small vesicles marked by the Thiery reaction; and, then, larger ones, which react negatively to this previous reaction. The endoplasmic reticulum increases considerably. The number of ribosomes and polyribosomes becomes very important at the beginning of the differenciation. At first, the mitochondries are very numerous, some of them remain, with dictyosomes and reticulum until the end of the cytoplasmic degeneration.
Roots of Vicia faba were treated with 0.0125% colchicine for 3 h. In the following 8 h mitotic indices increased in primary and lateral roots and in small primordia; it rose to 27.3 in lateral roots. When the colchicine treatment was followed by treatment with 5-aminouracil the increase in M. I. was suppressed; M. I. decreased progressively as the duration of 5-AU treatment was; 1) increased from 3 to 6 and to 8 h and, 2) as the interval between the end of the colchicine treatment and the start of 5-AU treatment was decreased from 5 to 0 h. An 8 h treatment with 5-AU reduced. M. I. in laterals to 1.7; this value is similar to that seen after treatment with 5-AU alone for 6 h, i.e. 1.8. Colchicine stimulates cells to complete interphase at an accelerated rate. But since the cells that respond to colchicine are blocked by 5-AU it is concluded that colchicine exerts its effects on cells in G1 (or G0) or the S phase. The results are discussed in terms of heterogeneity of cell cycle duration and how it may be controlled.
The synnema of Sphaerostilbe repens is a bundle of closely packed and mostly parallel hyphae. The synnemal tip gives rise to conidia. Stabilization of the stucture is established by numerous hyphal anastomoses, connections between cell walls (either directly or through the medium of mucilaginous substances produced by the cells), and by the branching of a few hyphae. Only the outer hyphae of the synnema exhibit wall ornamentations which seem to represent mucilaginous products excreted and subsequently condensed by dehydration. Ornamentations, mucilaginous compounds accumulated between hyphae and cytoplasmic membranes which appear to be very sinuous, stain positively for polysaccharides.
Morphological features and DNA content of nuclei at an early stage of development of the gametophyte of Lepisorus thunbergianus were observed. 1. Nuclei of the cells of the young gametophyte were globe-shaped at early stage of cell age and became ellipsoidal-fusiform by age. 2. The initiation of apical cell groups started just after the beginning of two dimensional division of the apical cell of the linear gametophyte. This is considered to be the signal for proliferation in these cells. 3. Nuclear DNA content was constant at the 1C level in all of the cells of young gametophytes at both linear and flat stages, except for the apical cell of the former and the apical cell groups of the latter which varied from 1C to 2C. Both the development and differentiation of the cells of gametophyte were found to be carried out at 1C level.
The autotetraploids of Trigonella foenum-graecum (2n=4X=32) showed an unfavourable response to colchicine and dimethyl sulfoxide treatment to produce octoploids. It resulted in the production of mixoploid plants. Some PMC's of mixoploid plants showed less than 32 chromosomes suggesting that somatic reduction had occurred at some stage of growth after the treatment. A few PMC's with octoploid chromosome number (2n=8X=64) were also observed. All mixoploid plants were sterile. Tetraploidy seems to be the upper limit of ploidy in this species.
X-ray-induced chromosomal aberrations have been examined by both light microscopy and scanning electron microscopy. It appears that the backbone of a chromosome consists of basically DNA which can be stained by various dyes and identified by light microscopy. The external material will not be stained by the similar dye, but can be observed by scanning electron microscopy. However the constituents of these external materials have not been identified microscpoically. The healing of a chromosomal break should involve both external and internal materials. A chromatid exchange may exhibit unstained space at the joint of two chromatids. However, such space is not observed by scanning electron microscopy.
The development of the massive structure which appeared as a protuberance of the internal cell wall and is composed of the insoluble state of anthocyanin, was morphologically observed using a black rose cultivar, Charles Mallerin. The massive structure initiated in the various appearances, for example, thread-like, T-shaped, L-shaped, auched, meteoric and so on, in the portion near the tip of the upper epidermal cells of the petals in the early age of half-opened stage of flowering. With advance of the flowering age, the young massive structure undergoes a marked increase both in length and in thickness. In further progress of flowering age the rod-like, sometimes branched, feature of the structure appeared and grew longer and thicker occupying the large portion of the central vacuole of the epidermal cells. The relationship between the massive structure and the tonoplast was discussed.
Chromosome systems of 12 genera and 36 species of the North American Decticinae have been studied. The chromosome number of these species ranges from 2n=22 to 2n=31 in the male (see Table 2). Robertsonian changes has played an important role in chromosome evolution in these decticines. Neduba sp. has a neo-XY sex determining mechanism and Neduba diminutiva an X1X2Y one. The probable pathways of chromosome evolution and the origin of the neo-XY and -X1X2Y sex determining mechanisms are discussed, as well as the phylogeny and present taxonomic status of the North American Decticinae based on chromosome systems.
The development of the prolamellar body in young (2-8-day-old) apical leaf etioplasts of dark-grown pea seedlings (Pisum sativum L. var. ‘Alaska’) has been examined at the ultrastructural level. The early stages of prolamellar body biogenesis involves the formation of discrete stroma tubules. Subsequently (8 days), these tubules aggregate into tubular strands which move centrally, serving as orientation points for the later development of the lattice-tubuleframework that ultimately develops in the stroma. The developing crystalline portion slowly assumes a hexagonal arrangement and ultimately becomes the “crystalline core” of the prolamellar body. Thylakoid membranes emanate out from the crystalline portion of the prolamellar body into the peripheral areas of the etioplast stroma. The relationship of prolamellar body development in pea tissue is discussed with respect to similar organelles described at the fine structural level in etioplasts of other plant tissues.