Artemisia maritima growing in Gurez (Kashmir) has been studied cytologically and is a tetraploid with 2n=36. The microspore meiosis is characterised by asynapsis, complement fractionation, nondisjunction of chromosomes, univalency and occurrence of restitution nuclei. There is an upset in timing relations of meiosis resulting in an aberrant meiosis which has been described fully. The initial movement of the chromosomes towards poles at Al is reversed towards the equator and a restitution nucleus is formed. A wall is secreted by such a P. M. C. and this assumes the appearance of a pollen grain. Although interesting irregularities were observed in 1st division of meiosis, the post-restitution division is comparatively regular. It is suggested that this tetraploid has originated as a result of wide hybridization and is thus an allopolyploid.
1. Saccharum spontaneum from Sikkim is the first report from this area. It is found to be 2n=56 as same as Debra Dun form. 2. The ligule pattern of Sikkim wild sugarcane is grouped into three, mostly round deltoid like as Japanese forms, few of acute deltoid as Madras form, and rarely falcate form like as Roxburghii in Formosa. 3. Manila form is 2n=80 which agrees with the former reports. 4. Comparative morphology of Manila form has never been reported. The ligule pattern is round deltoid as like as Japanese forms. Hair group 56 is mostly absent which was generally seen in the Sikkim as well as Japanese forms.
During the study of the somatic chromosomes, it was noted that two good table varieties, viz., Safet-velchi and Met-halal were having the chromosome number 2n=22 and thus were sterile diploids. The cytological studies of these varieties are presented. There were as many as 6 types of chromosomes in Safet-velchi and 5 types in Met-balai. Karyotypic formulae for these varieties were E4I1K6L4M2N5 and E4K6L4M2N6, respectively. Karyotypic variation and doubling of chromosomes in the somatic cells were also observed in Safet-velchi. During diakinesis, besides bivalents, univalents in varying numbers were noted. A maximum of one trivalent in Safet-velchi and two in Met-balai, per nucleus were found. Metaphase plates with typical bipolar spindles were rarely met with. The range of bivalent formation was between 6 and 7 out of the expected 11 bivalents. But the frequency of univalent formation was very high up to 56 percent with a range of 7 to 22 univalents per nucleus. Occassionally, PMCs containing a chromatid bridge and fragment at anaphase I was seen in both the varieties, indicating inversion and structural alteration of chromosomes. The chromosome movement during anaphase was irregular. In many cases, one of the divisions failed, with the result that the second division metaphase plates were rather rare. In cells where the second division took place, the chromosome distribution was highly irregular. Apart from this, lagging chromosomes formed micronuclei in the cytoplasm, leading to the formation of more than 4 microcytes. The pollen grains degenerated. The pollen was 95-98 percent sterile. These observations lead to the inference that Safet-velchi and Met-balai are probably one and the same variety; the minor differences found between them are attributable to the changes brought about by change in the environmental conditions. It might also be probable that these two varieties might have evolved from the same parental types by hybrid origin. The few bivalents found during meiosis in these two varieties may be said to be due to non-homology of many of the chromosomes brought about by structural alterations or by interspecific crossing. Isolation of these sterile diploids, induction of tetraploidy by colchicine technique and further crossing these with parthenocarpic diploids, have been suggested to be good method for the production of edible triploid bananas.
The present investigation was carried out on three species of Typhonium and two species of Arisaema. Their numbers are given below- Typhonium trilobatum Schott……… 2n=18 T. inapinatunz Prain……… 2n=26 T. cuspidatum Bl……… 2n=16 Arisaezna tortuossum Schott……… 2n=24 A. sanguineum Schott……… 2n=28 2n=16 chromosomes in T. cuspidatuin suggest that the basic number is lower than the one previously found. Meiotic study suggests that all the three species maintain homozygous state. Karyotype analysis shows a similarity between T. trilobatum and T. inapinatum. whereas T. cuspidaturn with fairly long chromosomes and characteristic C type of chromosomes with secondary constrictions represents a primitive level as compared to others. So, it has been suggested that it will be in a more natural position if placed under a separate subgenus. In Arisaema, the number 2n=24 in A. tortuossuni is new for the genus and the two species show clear similarity in their karyotypes. It has been suggested that aneuploidy along with structural changes of chromosomes has been effective in the evolution of this genus. Cytological data have confirmed the close relationship of the two genera.
1. In the cavity enclosed by an overarching of young leaves of Azolla imbricata, many hormogones of imprisoned blue-green alga (i.e., Anabaena azollae) are observed. 2. In cells of this blue-green alga, a system of complex lamellar structure is seen. 3. In the heterocysts, keritomie takes place generally. 4. In daughter cells budded from the heterocyst, a system of complex lamellae is seen. 5. Inner and outer membranes of heterocyst in Anabaena are composed of doubled layers respectively.
In the electron micrographs of the leaf in Azolla imbricata, the following could be observed. 1. In the young cell wall, plasmodesmata are well observed. 2. In the leaf cells, Golgi apparatus and endoplasmic reticulum not so many are observed as in cells of roots or root hairs. 3. Immature plastids in the leaf cells show similar structures to those observed in root cells or the root hair ones, while mature plastids show well differentiated grana-lamellae similar to the plastid common in higher plants. 4. It is concluded that the plastids found in Azolla roots or root hairs have an ability to change to chloroplasts.
Meiotic behaviour of two X-ray induced mutants of Pisuin sativum showing reduction of number of chiasmata was analysed. As a consequence of presence of many univalents in the pollen mother cells manifold irregularities appeared during the later stages of meiosis causing a high proportion of non-functionable germ cells. Corresponding abnormalities are realized in macrosporogenesis resulting in a high reduction of fertility. Clear differences between both of the mutants were observed in several subsequent generations in respect of the degree of meiotic irregularities and seed production evidencing that the mutants are not identical. It could not be clarified so far whether two different genes or two alleles of a multiple series have changed.
1. Unusual crystalloids were found in the cytoplam of mice lung cells. 2. Most of the crystalloids are rods or ellipsoids. They are surrounded by a layer of fine granules and are sheathed with an outer membrane. They have the size about two to four times longer than the mitochondria. 3. It is suggested that the crystalloid may be formed by the smoothwalled endoplasmic reticulum and their contents are phagocytic or secretion products of the cell.