Dry seeds of Trigonella foenum-graecum were exposed to 10, 30 and 60 Kr of gamma rays. Germination was observed first in 60 Kr followed by 30 Kr while in 10 Kr and control germination was simultaneous. There was initial stimulating effect of higher doses on root growth and division frequency but after few days both these were negatively correlated with dose. Frequency of abnormal cells increased with dose. Appearance of chromosomal rings is explained on the basis of telomeric losses and intra arm exchange type. At 60 Kr there was no growth beyond 2 cotyle-donary stage due to adverse effect on cell nuclei in growing region. Differential response of roots, shoots to radiation has been discussed.
Crosses between the grain sorghum species, S. subglabrescens (2n=20) and a diploid race of S. halepense (2n=20+4-6 B's) yielded F1s exhibiting constant and oscillating number of accessories only in the PMCs. Six hybrids showed only 4, two F1s had 4-6, in two others the accessories ranged from 6-8 and in one from 8-10. In the last hybrid, 6, 8 and 10 B chromosomes could be found in PMCs of an anther. The size of the accessories was not appreciably large compared to the A-chromosomes and the former occurred only in pairs. They segregated independently of each other and exhibited normal separation, delayed disjunction, elimination and en-bloc movement at AI. Lagging of the B-chromosomes also occurred at AI and AII leading to their expulsion. Three B-pairs, B1, B2 and B3 could be recognised of which the former two presented configurations involving four or more chromosomes depending on their numerical strength. The presence of the B3 in all hybrids emphasises the importance of coexistence of accessories in gametes of the male parent for successful cross pollinations.
Colchicine induced autotetraploids of Zinnia linearis were taller, had thicker stems, larger leaves and ray florets and capitula of greater diameter than diploids. The autotriploids presented increased values in respect of thickness of stem, number of branches and length of peduncle compared to the tetraploid but were more or less intermediate between the parental forms with regard to height of plant, size of leaf and ray floret and diameter of capitulum. No linear relationship could be traced between the meiotic aberrations and sterility in the tetraploids. Factors of a genetic nature seem to be superimposed over those of cytological origin in determining sterility. The differences in pollen and seed fertility and the occurrence of parthenogenetic diploids are impediments to quick progress in selection. In the triploid, the concomitant sterility enhances the vigour and ornamental value. The haploid complement of Z. linearis appears to be constituted of two basic sets of 5 and 6 chromosomes, the former possessing identical homologues while the latter having only partially homologous partners in the diploid complement as reflected in the expression of preferential pairing in the tetraploid. This differential pairing behaviour is also evident in the meiosis of the autotriploid. It is probable, that hybridisation between two putative types with 5 and 6 (n) chromosomes could have contributed to the development of this ornamental species.
Three genera viz. Hibiscus, Azanza and Urena are considered for the present investigation. Of the five species of Hibiscus analysed H. panduraeformis seems to be most primitive while, H. vitifolius and H. cannabinus are slightly more advanced. H. lobatus and H. sabdariffa have medium to very short types of chromosomes and show higher ploidy levels, and thus be considered more advanced than others. The problematic status of the genus Azanza is reviewed in the light of our findings, which ascertains the maintainance of distinct generic status and be placed inbetween Thespesia and Hibiscus. The more evolved nature of Urena sinuata is ascertained by the presence of 2 super-numerary, secondarily constricted and satellited chromosomes in the complement. Existence of cytotypes within the circumscription of species is suspected. Regarding the basic number for the family, it is concluded that 6 can be the basic number, found in more than one genera; and evolution must have taken place along divergent lines among the genera and species. The course of evolution within the family might be through ploidy accompanied by structural changes in different combinations.
The histogenesis of the nests of intimately associated neurons (isogenic groups) of the avian brain is autoradiographically studied. The cellular specificity (glial or neuronal) of the labelled cells included within differentiated isogenic groups as well as the labelled double satellite cells of individual neurons is briefly analized.
The changes in insoluble reserve materials, such as starch, lipids and protein, and the cytoplasmic RNA in soybean cots upon germination have been investigated using optical histochemical techniques. Day 4 and day 5 seem to be significant period in the activity of the cotyledons as far as the metabolites are concerned. The starch grains attain a peak by this time and undergo degradation thereafter. The PBs increase in size due to swelling or coalescence or both by day 4 and show a porous, granular core and a loose peripheral ring. A temporal stepwise frag-mentation in PBs beyond day 4 is marked by a topological progression from without on both sides of the cots. The oil globules show accelarated depletion beyond day 5. All the reserves have almost disappeared from most cells by day 11 to day 14. The cytoplasmic RNA stainability decreases with progress in germination concomitant with the degree of depletion of reserves.
1. Karyomorphological studies in a garden variety of aloe suggest that it is an interspecific hybrid. 2. The diploid complement shows 14 chromosomes, of which one long and one short have secondary constrictions and are without homologues. 3. The karyotype has been discussed in relation to probable parents of the plant. 4. In majority of the dividing cells, various types of mitotic abnormalities during metaphase and anaphase have been recorded. 5. The mitotic imbalance is in all probabilities due to hybridity.
Chromosome banding techniques have been used to compare the karyotypes of Pieris rapae and P. napi. The basic complements (both n=25) are very similar but clear differences are present and these are discussed in detail. (A brief comparison is made with Pieris brassicae, n=15). Cytological techniques have confirmed the presence of a constriction (primary centromere) in the Pieris species and also in a member of the Satyridae (Pyronia tithonas, n=29). Supernumerary B-chromosomes were discovered in both P. rapae and P. napi. Hitherto these have been reported only in the Japanese races of these species and in a small number of Finnish P. rapae individuals and it has usually been assumed that they are absent from populations in the rest of the world. The characteristics of the B-chromosomes differ both numerically and struc-turally between the two species and the variations are discussed. No phenotypic differences exist between individuals with and without B-chromosomes.
Cytological observations have been made on 12 species. Hemigraphis latebrosa var. rupestris (n=14), Lepidagathis incurva var. mollis (n=42) and Peristrophe speciosa (n=30) provide the first reports for these species. Justicia quinqueangularis var. peploides with 2n=18 is the first report for this variety. The chromosome number of Thunbergia erecta (n=31) and Lepidagathis purpuricaulis (n=11) are different from the previous reports for these species. The occurrence of aneuploid or polyploid cytotypes within limits of “taxonomic species” are evident in Thunbergia erecta (2n=52, Ca. 56, 60, 62, 64), Blepharis maderaspatensis (n=13, 15), Lepidagathis purpuricaulis (n=11, 42), Rungia parviflora (n=8, 15, 25, 26), and Peristrophe bicalyculata (n=10, 15). Dicliptera roxburghiana revealed abnormal meiosis. The irregularities in chromosome behaviour comprised univalence producing segregational errors and “tetrads” with variable number of unequal sized pollen grains.
Meiotic studies indicated that EMS (0.25%) and MMS (0.025%) induced a large number of aberrations such as reciprocal translocations comprising rings and chains of 4, 6 and 8 chromosomes; inversions consisting of chromosomal and chromatid bridges and fragements, laggards; and unequal distribution of chromosomes. In a few cases rings of 6 and 8 chromosomes were found in the same PMC, indicating that all the 7 pairs of chromosomes were labile to the action of these mutagens. Reduction in chromosome aberrations in M2 and M3 and a slight increase in M3 over M2 was observed in all treatments. Post treatment with gibberellic acid at 1000ppm effectively reduced the chromosomal damage in M1 and was more effective in the case of MMS than EMS. The aberrations in M2 and M3 in gibberellic acid post-treated plants were decreased as compared to M1 generation.
Cytomorphological studies in Convolvulus arvensis and C. pluricaulis revealed n=16? (4X), 24 (6X) for the former and n=9 (2X), 2n=36 (4X, abnormal meiosis) for the latter species. The morphological variations in C. pluricaulis appear purely to be due to change in ploidy level, both the diploid and the tetraploid taxa in this species seem to have attained genetical diversity through long periods of time. In C. arvensis, the ecological factors, gene mutations, chromosomal repatternings and possibly ploidy level seem to be responsible for morphological diversity.
Cytology of four clones of S. littoreus from 3 different radiation levels at the monazite area at Manavalakurichi and one from Kovalam, a nonmonazite area was examined. The plants from Kovalam showed 9 bivalents in PMCs and 18 chromo-somes in root tip cells. The clones I and II from Manavalakurichi showed very high frequency of PMCs with interchange configurations and clones III and IV showed very low frequency of a ring of four chromosomes and fragments in PMCs. Analysis of the translocation configurations and their frequency in clones I and II has revealed that there are at least 3 translocations of long standing in each of them, in two of which a single homologous pair of chromosomes is involved. It is shown that one of the interchanges is either common to clones I and II or at least involve exchanges of almost equal sized segments between the same chromosomes. The occurrence of a low percentage of quadrivalents in clones III and IV is suggested to be the result of interchanges occurring in microsporocytes in these plants. The chromosome breaks prior to the formation of these interchanges and fragments in the PMCs in clones III and IV are suggested to be induced by natural radiations from monazite. The translocations of long standing in clones I and II are also shown have occurred as a result of natural radiations in these long established species. The occurrence of these chromosome aberrations in S. littoreus alone of all the plant species in this area and its persistence is attributed to its creeping growth habit and capacity for vegetative propagation.
The karyotypes of two species, Milvus migrans and Accipiter badius belonging to family Accipitridae, order Falconiformes have been studied. Both of them were found to have the same diploid chromosome number, i. e. 66. The demarcation between the macro- and microchromosomes is not sharp in either case. The Z-chromosome in Accipiter badius is an sm chromosome being the largest of the whole set and the W is a small T chromosome. In the absence of female plates we could not identify the Z and W of Milvus migrans.
The chromosomes of 6 species of cottoid fishes from Japan are studied. Trachidermus fasciatus and Cottus kazika have the diploid number of 40, the arm-number being 64 in the former, while 58 in the latter. The remaining 4 species belonging to the genus Cottus have the diploid number of 48. The arm-number is 58 in C. pollux and C. nozawae, 54 in C. hangiongensis, and 60 in C. reinii. The taxonomical relationship between the 48-chromosome group and the 40-chromo-some-group are discussed on the basis of the chromosome morphology.
The spermiogenesis in the sea urchins, Arbacia lixula and Echinometra locunter, has been investigated by means of electron microscopy. In the gross morphological aspects sperms are similar and show three main parts: the head, the short middle piece and the flagellum. The nuclei of developing spermatids are irregulary shaped with a less condensed chromatin and a prominent nucleolus. A very dense globular inclusion was a common characteristic of this stage. Throughout differentiation sperm cells are connected by intercellular bridges. The complete isolation of the four spermatozoa from each spermatocyte results only when there is no more cytoplasm in the cell.
This study follows the ultrastructural changes that take place in endosperm tissue during the early stages of embryo development in Quercus gambelli; i.e. from the two-celled embryo through the heart stage. Although the degree of change varies, similar sequences in endosperm transformations are present at all stages examined. The formation of cytoplasmic islands by a pinching off action of the tonoplast is characteristic of early transformation. The endoplasmic reticulum (ER) changes from the rough, lamellate type in early stages to an entirely vesiculate type until it finally disappears from degenerating cells. The vesiculate ER cisternae are usually lined with ribosomes and often contain various osmiophilic inclusions. Plastids are numerous and highly variable in shape. They are characterized by the presence of osmiophilic bodies, and rarely contain starch. Lipid bodies are present at all stages, but never in large quantities. Mitochondria lack osmiophilic bodies; in degenerating cells they are surrounded by osmiophilic deposits, and the cristae lose their integrity. Polysomes are present in all stages examined, except in degenerating cells where the cytoplasm becomes so dense that ribosomes and other cytoplasmic components are indiscernible. The developing cell wall has many discontinuities in section view. Numerous plasmodesmata are present, but they disappear from the common wall between degenerating cells. Dictyosomes appear to be associated with cell wall growth; they disappear in degenerating cells. The plasmalemma in degenerating endosperm cells becomes distorted and disrupted at places, but the tonoplast appears intact. Although various possibilities are discussed, it is concluded that the endosperm of Q. gambelii does not have a major function as a food storage tissue (as evi-denced by the low amount of starch and lipids) but rather, it serves as a translocating tissue between the food source (stored food within the outer integument, and food coming into the ovule through the vascular supply) and the embryo. The cotyledons, thereby, become the storage area within the developing and mature seed.
Observations on the morphology of spore-forms of Ravenelia hobsoni Cke. revealed the presence of pycnia, uredia and telia in its life cycle. The latter two are described in detail. Teliospore germination, meiotic nuclear division in the basidium and mitosis in basidiospore are explored and illustrated. The haploid chromosome complement appears to be 5 (n=5).
Taphrina maculans Butler, a causal agent of leaf spot of turmeric (Curcuma longa L.) forms two types of colonies namely “salmon-red” and “creamy-white”. The former strain dies abnormally under optimal nutritional conditions while the latter does not behave so. Electron microscopic observations of both the strains manifest for the first time, an extra intracellular outgrowth from an undetermined site of cell wall that grows further traversing the entire cellular part resulting into the death of the cells. The dead cells become white. The plasmamembrane pro-bably extends further during the synthesis of the extra outgrowth material serving as the boundary wall between the extra outgrowth and the cytoplasm. Such phenomenon of extra synthesis of cell wall material that causes the death of the cell has been observed in the salmon-red strain only.
This paper presents the standard banding pattern in the salivary gland chromo-somes of Anopheles jamesi, a member of the subgenus Cellia. Mosquitoes were collected from the cattle-sheds in the thick forests of Khasi and Jaintia hills of northeast India (Assam). Attempts have been made to compare the banding pattern of the salivary chromosomes of the present species with those of other species belonging to the subgenus Cellia and to draw a cytological relationship among them. The observations reveal that there are several areas in the autosomes of these species which are homologous. The X-chromosome, however, shows considerable differentiation in its banding pattern.
Green spores of Equisetum arvence retained 16-64% viability after about one year of storage at minus 20°C. Judging from ultraviolet absorption and various chemical tests, release of proteineous substances from spores in the medium increases correlatively with the length of storage. Fresh spores do not diffuse protein, dissimilar with germinating pollens of higher plants. It is concluded from the present and other results that spore membrane deterioration is one of the causes of low viability. Osmunda japonica bearing chlorophyllous spores and Pteris vittata bearing non-chlorophyllous spores retained high vitability in various organic solvents, but Equisetum arvence did not.
The paper presents comparative studies of diploids, tetraploids, triploids and hexaploids of Tabernaemontana divaricata. Hexaploids were artificially induced from natural occurring triploids. They are characterised by enhancement in plant parts but slow growth rate. The instability in number of stamens observed at triploid level is further enhanced in artificially induced hexaploids. These hexa-ploids show regular meiosis and low multivalent frequency. Pollen fertility was increased from 15% at 3n to 78.96% at 6n level.
Cytology of ten species of Vernonia indigenous to South India has been studied, viz. V. beddomei (n=9 and 2n=18); V. cineria (n=9 and 2n=18); V. divergens (n=9 and 2n=18); V. conyzoides (n=9 and 2n=18); V. albicans (n=9); V. penin-sularis (n=9); V. indica (n=18); V. anthelmintica (n=10 and 2n=20); V. bourneana (n=10 and 2n=20) and V. elaeagnifolia (n=20 and 2n=40). Chromosome records show that the Indian members of the genus fall under two basic series, x=9 and 10, of which the former group shows greater preponderance. The x=10 species are considered to be the earlier evolved ones and those with x=9 diploid species are suggested to be aneuploid derivatives. Polyploid frequency is very low in the genus. V. indica and V. elaeagnifolia reported here are the only polyploids so far known, both being allotetraploids. Karyotype study is made for the first time in this genus. Data of karyomorpho-logy on seven species indicate that the karyotypes of the diploid species are unspeci-alized and it appears that factors resulting in karyotypic specialization have not been significantly operative in the evolution of species of Vernonia.
Cytology of three interspecific F1 hybrids in Brassica referred to in the text as Hl, H2 and H3 obtained by crossing B. napUs var. oleifera (n=19), B. campestris var. oleifera (n=10) and B. chinensis var. communis (n=10) was studied. The associations formed by the chromosomes of the genomes ‘a’ and ‘c’ were sorted out and the homologies have been assessed on the basis of their pairing at pachytene. The chromosomes of the ‘a’ genome contained in the three diploid species involved in the crosses are found to be homeologous from their complete pairing at pachytene. The affinities of the genomes ‘a’ and ‘c’ are found to be very feeble in terms of their synaptic relationships. The conclusion is arrived at by using information regarding the bivalents observed in the F1 hybrids of the present study together with those observed in amphidiploids and F1 ‘ac’ hybrids obtained by earlier workers.
Aneuploids have been identified among progeny from the homozygous recessive desynaptic soybean mutant T258. Most progeny examined from three different years were near the diploid chromosome number. The aneuploids varied in chromosome number, pollen fertility, seed set, and transmission of the extra chromosome. The fertility and transmission rate of the extra chromosome are adequate for use of aneuploids in further cytogenetic studies. Evidence indicates that certain 40-chromosome plants are genomically unbalanced, but viable. Such plants offer opportunities for developing addition-substitution lines.