Vicia faba seeds (var. Giza 1) were irradiated with: 500, 1000, 2000, 4000, 6000, 8000, 10, 000r of Co60 γ-radiations. A rapid increase in the percentage of abnormal cells in root-mitosis was observed as the employed dose increased from 8000 to 10, 000 r. The same doses affected a high degree of inhibition in root-growth. The change in the normal cells was proportional with the given doses. Micronucleated cells represented the most dominent type of anomalies affected by irradiation. Plants originated from irradiated seeds recovered. A significant percentage of abnormal PMCs was observed only in plants originated from seeds irradiated with 10, 000 r.
A review of the results of cytomorphological observations so far carried out on members of Asplenioid and Athyrioid ferns from the Himalayas is given. The results from this phytogeographically important region are compared with other areas having temperate and tropical climates. It is concluded that the percentage and rate of polyploidy is definitely lower in the Himalayas as compared to the tropical areas. This region contains a very high proportion of diploids and is different from rest of the Indian sub-continent (South India and Ceylon) where there is greater incidence of polyploidy. Also the flora of the Himalayas resemble the flora of Europe and North America in this respect. Evolutionary mechanisms at work in members of the four principal investigated genera, namely, Asplenium, Cystopteris, Athyrium and Diplazium are also considered. Asplenium shows a marked predisposition for evolution through polyploidy which is detected in 72.2% of total taxa investigated throughout the world. As compared to this, in Athyrium the great majority of the species are at diploid level (about 56% taxa). Diplazium shows 56.7% polyploid taxa, largely composed of tetraploids. Apogamy is frequent in Asplenium and Diplazium whereas it is almost absent in Athyrium and Cystopteris. It is now evident that in Asplenium, Cystopteris and Diplazium hybridization and polyploidy (both allo- and auto-allo) have played a significant role in the evolution of species, but not to that extent in Athyrium where the evolution has been principally through genic mutations.
This paper reports the effect of abscisic acid (ABA) on the root growth in Allium cepa and the effects on the growth components, namely, cell flow and final cell size, and number of functional cells in each meristematic rib. With a continuous treatment by ABA steady state kinetics of growth is attained for each concentration, characterized by a constant growth rate. This growth is inhibited only by ABA 10-5M, 10-6M and 10-7M. The 10-7M concentration seems to act only on the cell size. At ABA 10-6M a slight decrease in the cell flow is also observed and at 10-5M the results suggest a decrease in the number of functional meristematic cells, in addition to the other two previously recorded effects. All these results are compared with those obtained by the same ABA concentrations in the short term experiment.
The meiotic chromosomes of the chimpanzee, Pan troglodytes troglodytes, were studied in detail and the different stages of division are depicted. Special attention is given to the chiasma formation in the autosomal bivalents and their fate in the successive stages of the first meiotic division. No chiasma was found between the sex elements X and Y which are associated end-to-end during the course of first spermatocytic division. The average number of chiasmata per cell of the chimpanzee is of the same order as that of man.
Meiosis could be studied in only three taxa, Z. candida (2n=41) and cvs. with 2n=48 and 50. When taken in conjunction with other data, it is clear that in tetraploid taxa (2n=24) generally there is normal meiosis with 12 II but at higher polyploid and aneuploid levels, a low number of multivalents in the form of rings or chains involving 3 to 8 or even more chromosomes has been consistently found. The number of chromosomes within an interchange complex is often more than the level of polyploidy, implying thereby that most of the higher ploids are complex interchange heterozygotes. Evidently, bivalent formation in tetraploids indicates that the differentiation of the chromosomes is relatively high at that level, but at higher levels chromosomes are homoeologous and form multivalents and interchange complexes. It follows, that lower ploids are alloploids with relatively simple constitution but higher ploids are complex interchange heterozygotes. This conclusion is in line with the karyotypic analysis. Although recombination in the latter is expected to contain a number of disharmonious combinations, but because of the large amount of duplicated material, the amount of sterility is not particularly high. Due to cross pollination, the process of building up of increased level of genetic complexity continues.
Comparative analysis of chiasma frequencies and terminalization in nine tetraploid species of Triticum have been studied at late diplotene/diakinesis and metaphase. Total number of chiasmata per cell was found to be maximum in T. timopheevi and wild species T. dicoccoides and minimum in cultivated species (T. dicoccum). Similar trends for mean number of chiasmata per 100μ of bivalent length were noted. Variations in the number of bivalents with zero to four chiasmata do exist among the species studied. Maximum number of bivalents with four chiasmata was noted in T. timopheevi suggesting random distribution and least linear differentiation among wild wheats. This situation has been further confirmed from the highest proportion of interstitial chiasmata both at late diplotene and metaphase in T. timopheevi and T. dicoccoides. Cultivated species like T. dicoccum had maximum number of bivalents with zero to one chiasma. Correlation coefficients between total bivalent length and total number of chiasmata per PMC were found to be significant at 0.05 or even 0.01 level. These comparative studies on chiasma frequencies, distribution and terminalization suggest that individual species differ in respect of linear genetic differentiation of their homologues.
Four chromosomally aberrant progeny of a selfed trisomic E. erythropoda were analyzed. Of these, two were reconstituted trisomics for the parental mediumlong chromosome; however, one bore an additional trisomic short chromosome and the other a fragmented medium chromosome. In the third plant one of the medium-long trisomic chromosomes bore an interchange segment of a non-homologous short chromosome and was thus a tertiary trisomic. In the last case the plant was trisomic for a medium chromosome only.
The cytological effects of five lathyrogens, viz., βAPN, βCA, βODBA, βOAA and 2, 4-DBA were studied on Vicia faba L. Only one concentration of 0.1% was used for 3 different soaking periods. All the lathyrogens caused cytological abnormalities to some extent or other. Immediate steps should be taken to breed lathyrogen-free Lathyrus sativus.
Detailed studies on total chromosome length, relative length and arm ratio in BIL-4, an inbred of pearl millet, have been made to facilitate identification of trisomic and translocation stocks developed in this inbred. Significant differences in karyotype have been observed at varietal level.
The dry masses of isolated polyploid nuclei from somatic tissues of bees may be established by micro-interferometric procedures and are often in accordance with cytophotometric values for DNA. Increases over those expected from polyploidy in nuclear volumes and in nuclear dry masses of Melipona quadrifasciata Malpighian tubes may be due to non-histonic proteins, but in Melipona quinquefasciata such increases are also probably concerned with hydrating factors. The histone content removed by trypsin in the last larval instar of Melipona quadrifasciata is higher in the silk glands than in the Malpighian tubes, perhaps due to a large repression of genes not concerned with protein synthesis in the silk glands.
Cytogenetic studies of bone marrow preparations and/or whole blood cultures were carried out in 18 patients with myeloproliferative disorders. The Ph1 chromosome was detected in six of nine patients with chronic myeloid leukemia. Chromosomal abnormalities included: group C trisomy in a patient with myeloid metaplasia, and a 46 chromosome karyotype but with a missing D group and an extra C group chromosome in a patient with chronic monocytic leukemia.
Cytological account based on meiotic studies of 23 taxa belonging to Ranunculaceae is presented. Eight species have been investigated for the first time and three intraspecific races have been discovered. Chromosomal aberrations are recorded in Anemone obtusioloba, Ranunculus hirtellus, R. laetus, Delphinium cardiopetallum and Aconitum kashimiricum. It is inferred that the original base number of the family is x=4 and early in its evolutionary history it became doubled so that the prevalent haploid number in the family is n=8. Evolutionary diversification in the family has involved alterations in chromosome number, karyotype changes, polyploidy and of course gene mutations.
In the spermatid of pig tail monkey, a floral body consisted of clusters of tubular elements was found near the acrosomal vesicles. The dimension of this organelle was 1 to 3μ and the diameter of the tubules was approximately 250Å. It is possible that this structure may represent a modified Golgi apparatus. The mitochondria were uniformly distributed in the cytoplasm. The center portion of the mitochondria was often free of cristae.
Hybrid between Solanum gracile naturalized in New Zealand and an Indian race of S. nodiforum had 84.3% pollen sterility and did not set seed. Chromosome pairing observed at late diakinesis suggests that the genomes of the two species differ in at least three pairs of chromosomes and probably two of these three pairs are involved in a translocation for a short segment. Sterlity of the F1 hybrid is largely due to genic imbalance of the gametes rather than due to chromosome numerical imbalance.
Detailed microsporogenesis of two races of P. orientale has been studied. Chromosome pairing has been found regular in the diploid but irregular in the tetraploid. The frequency of quadrivalents observed in tetraploid seems to be high enough to suggest the autoploid origin. It has been suggested that polyploidy and meiotic abnormalities are mechanisms which favour apomictic reproduction in P. orientale. Two intra-specific chromosome races have been found in P. orientale. The taxonomic and plant breeding significance of intra-specific chromosome races has been discussed.
Breeding system, crossability relationships and isolation mechanisms have been studied in the Solanum nigrum L. complex, using 16 accessions including seven diploids, five tetraploids and four hexaploids. Of these six are Indian forms and special attention has been paid to them. It was found that the diploids could be crossed with each other and also with natural tetraploids fairly easily, but never with the hexaploids. Crosses between two tetraploids or two hexaploids readily produced hybrids. In general, in crosses involving two ploidy levels, a cross succeeds when the higher ploidy plant was crossed as the seed parent; but exceptions were found wherein the lower ploidy plant could be successfully used as the seed parent. In this respect all diploid races are not isolated from the tetraploid races to the same extent; some races were divergent enough to be crossed only as male parents while others could be crossed in either direction. Compared to this diver-gence in crossability relationships hybrids sterility seems to be the major hurdle for gene exchange between the diploids and tetraploids. The Indian diploid and tetraploid races are isolated to a lesser extent as compared to the European diploid and tetraploid races. Autopolyploidy reverses crossability relationships. The diploid S. nigrum of India as seed parent crosses with natural tetraploid S. nigrum of India but fails to cross with natural hexaploid S. nigrum of India. However, the autotetraploid of diploid S. nigrum crosses with natural hexaploid and fails to hybridize with natural tetraploid. In addition to self-pollination and geographic isolation as factors restricting gene exchange between the different forms, hybrid sterility, hybrid breakdown and hybrid inviability were found to be operative in the complex. Diploid and hexaploid races of S. nigrum of India are isolated by hybrid inviability, while the diploid and tetraploid races of S. nigrum of India are isolated by hybrid sterility.
A total of 80 Triticale lines was evaluated for meiotic stability, pollen and seed fertility. Sufficient variation between the lines was found in respect of all the three characters. Further, no correlation could be established between meiotic irregularity and pollen fertility, meiotic irregularity and seed fertility as well as between pollen fertility and seed fertility. Meiotic irregularity was supposed to be due to lack of coordination in meiotic rhythms between the chromosomes of the two parental genomes. The significant interline variation in seed fertility should indicate the possibility of developing highly fertile lines through selection.
The entire haploid complement of the pantropical diploid (2n=30) Ipomoea species, I. biloba Forsk has been identified at pachytene stage employing criteria such as relative length, centromere position, nucleolar association, distribution and length of dark- and light-staining segments in the arms and chromomere number, size and pattern of distribution. The diagnostic features of the differentiated pachytene bivalents and the idiogram at this stage are presented. The advantages of pursuing karyological studies at pachytene over that at somatic metaphase in this species is brought out. From a comparative study of pachytene karyotypes of I. biloba and the earlier investigated I. crassicaulis with which it has been recently hybridized, homoeology of eight chromosomes could be adduced. The need for pachytene analyses in this inter-specific hybrid, other releated species and their hybrids is emphasized. Later stages of meiosis were found to be normal leading to formation of over 95% stainable pollen.
The relative effect of maleic hydrazide, administered at the rate of 5 mg per individual, on the spermatocyte chromosomes of five species of grasshoppers has been studied. In the control species, the effect was practically nil. In the treated series, it was manifested in the form of chromatid and chromosome type breaks, laggards, bridges etc. The species arranged in decreasing order of effect, are: i) T. pulvinata, ii) P. antennata, iii) A. lugula iv) S. prasiniferum and v) O. velox. The differential responses have been critically analysed in various ways. Discussions have been made on the role of some influencing factors over the present data. The data have also been compared with the x-ray induced ones.
Our studies carried out in 4 breeds and two hybrids of carp (Cyprinus carpio) revealed a diploid chromosome number of 100, among which 24 pairs are twoarmed. These latter consist of 12 pairs of metacentrics and 12 pairs of submeta-and subtelocentrics.