After treatment of two varieties of Brassica campestris L. (2n=20), T10 and T151 with radioactive chemicals P32 and S35, having different concentrations, aberrant cells, for studying the effects were scored in meiosis. According to the nature of abnormalities in metaphase and early anaphase cytological effects and origin of different abnormal configurations were explained. Significance of probability of nature of abnormalities was estimated by X2 test and estimate of aberration rates were based on p=n-n/N and S.E.=√p(1-p/n) was also considered as proportion abnormalities to the total confidence limits. Sampling error was also calculated per treatment in percent to record optimum sample size for analysis. Linearship between treatments and cytological aberrations was shown.
1. The chromosome numbers of 64 species have been studied on which 56 are investigated for the first time. 2. Morphological, anatomical and cytological findings on the Musaceae in the broad sense are considered from a phylogenetical standpoint and three distinct groups: a) Musa-Ensete, b) Ravenala-Strelitzia-Phenakospermum and c) Holiconia are recognised as suggested by some authors. For these groups sub-familial status is proposed. 3. Lowiaceae have been studied for the first time cytologically and their chromosome morphology, distinct from that of any other group of Zingiberales, confirms their claim to familial status. 4. Consideration of the conflicting theories proposed to account for the higher chromosome number in genera like Globba, Alpinia, and Phaemeria, etc. leads to rejection of Chakravorti's hypothesis of wholesale fragmentation of chromosomes and the acceptance of the opposed view of Raghavan and Venkatasubban and others. 5. Holttum's transference of the genus Zingiber to the tribe Hedychieae has been given cytological support on the following points: a) the basic number in the genus Zingiber correlates with that of Kaempferia. b) the new tribe Alpinieae (which is infact Zingibereae without Zingiber) have consistently 48 chromosomes in their somatic complements. 6. It is suggested that the African representatives of Kaempferia should be given the status of genus; Cienkowskya on the following points: a) the difference in floral morphology b) geographical separateness and c) the difference in the number and morphology of the chromosomes. By comparing the present and past findings, various lines of evolution of the chromosome complements within each group are discussed. 7. The basic number 11 is considered to be probably the original one for the Zingiberales as a whole, being present in Ravenala which is the most primitive member in the order. From this secondary basic numbers have arisen through evolution.
Studies on cytology, pollen fertility and seed setting were under taken on the F1 plants of inter-varietal crosses in Brassica campestris L. to establish relationship between various self-compatible and self-incompatible forms. The Fl plants in general showed a regular meiotic behaviour. Generally the pollen fertility in these plants was quite normal as compared to the parents. Seed set was quite high in F1 plants of self-compatible forms lowest in F1 of crosses involving self-incompatible forms and moderate when one of the parents was self-compatible and other self-incompatible. The relationship among various self-compatible and self-incompatible varieties of Brassica L. is discussed.
Chromosomal preparations from fourth instar larvae (prepupae) were studied to determine the karyotypes of four genera and eleven species of mosquitoes. Although the chromosome number is the same in all species investigated (2n=6), nevertheless distinct karyotypic differences among genera and species were observed.
Translocation configurations have been studied in a structural heterozygote in Lycopersicon esculentum Mill. The quadrivalents and bivalents have been observed with a frequency of 32.8 and 67.2 percent respectively. The quadrivalents behave normally while the bivalents lag at AI because of the lack of movement of chiasmata over the non-homologous segments. This leads to meiotic abnormalities, like fragmentation, observable at AI and subsequent stages. Previously known cases of this nature have been reviewed and it has been suggested that the reported exceptions to this general rule may be explained on the basis of chromatid instead of chromosome translocations.
1. Paired as well as unpaired chromosomes were observed in pachytene. 2. Eighteen univalents are present at diakinesis; sometimes however, two univalents lying above one another give the impression of a bivalent. 3. Some of the univalents undergo fragmentation at diakinesis. 4. Meiosis II may fail to occur; dyads then form after the first division. 5. Irregularities in meiosis lead to the formation of supernumerary micro spores.
Meiotic studies of three P. typhoides×P. purpureum hybrids showed that the species P. purpureum (n=14) is an allotetraploid and contains 7 chromosomes of the diploid species P. typhoides. There was indication of certain chromosomal aberration in the species P. purpureum. The hybrids studied were highly sterile due to meiotic abnormalities. The cytological behaviour of the three hybrids studied was similar.
Six strains of strawberry have been studied from Kashmir occurring both in wild and cultivated state. The cytological studies on these have shown that the cultivated strain of strawberry at Yarikah Farm, Tangmarg, is a possible hybrid between the American strawberry F. chiloensis 2n=56 and European strawberry F. moschata 2n=42. The natural hybrid has 2n=49 chromosomes.
Chromosome numbers were determined during microsporogenesis in strains belonging to 21 species and 8 genera of Paniceae. These include 4 new reports. Intraspecific chromosome races were found in Brachiaria brizantha, Cenchrus ciliaris, Digitaria adescendens, D. eriantha, Eriochloa nubica, Panicum maximum, Paspalum, orbiculare, P. plicatulum, Pennisetum pedicellatum, Urochloa mosambicensis and U. panicoides. Meiosis was studied in all species. Chromosome pairing was regular in diploids but irregular in polyploids and aneuploids. It is suggested that polyploidy and meiotic irregularities are mechanisms which favor apomictic mode of reproduction in the members of Paniceae studied herein. The frequencies of quadrivalents observed in strains of Cenchrus ciliaris, Paspalum plicatulum and Paspalum simplex seem to be high enough to suggest their autoploid origin. In the rest of the species with low quadrivalent frequency, the factors favoring the accumulation of chromosome structural changes seem to be in operation. Of special interest was a plant of Digitaria eriantha, which exhibited the phenomenon of breakdown of meiosis. The pollen mother cells at early prophase were without well differentiated cell walls, due to which several nuclei formed cenocytes. A few cells showed fragmentation of chromosomes. The metaphase stage was never reached. The fragmented chromosomes formed restitution nuclei. A few cells formed multiple spindles. The pollen fertility was very low. The significance of the cytological findings was discussed.
The fine structure of some sixty different collections of blue-green algae representing at least thirty different species was studied. In addition to the usual components of blue-green algal cells, a number of different, unique, intracellular structures were observed. Membranous “stacks”, and “spheres”, and “scrolls” in which the membranes are not typical unit membranes are described. “Spheroids”, 25 to 30mμ in diameter, were found in intrathylakoidal spaces of several collections. Other inclusions, including a variety of filamentous and crystalline arrays, are described. It is suggested that some of these inclusions are intracellular symbionts.