A K SHARMA

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

A New Concept of a Means of Speciation in Plants

Caryologia

Karyomorphological studies were carried on three species of Haworthia Duval (family: Xanthorrhoeaceae) namely H. radula (Haw.) Duval, H. glauca Bak. var. herrei and H. limifolia Marl. var. keithii. Karyotyping through Image Analyzing System in three species of Haworthia (family: Xanthorrhoeaceae) reflected karyotypic orthoselection with same basic chromosome number (x = 7) and bimodal karyotype. In H. radula (2n = 14) two satellites were found one in each on the long arm of the two long chromosomes. H. glauca var. herrei and H. limifolia var. keithii possessed 2n = 28 somatic chromosomes. In addition pollen mitosis of each species was done. Pollens are endowed with expected number of n = 7 and bimodal chromosomes. Therefore karyotyping through Image Analyzing System suggests that H. radula is diploid (2n = 14) whereas H. glauca var. herrei and H. limifolia var. keithii are autotetraploid (2n = 28) plants. © 2013 Archana Sharma Foundation of Calcutta.

Nucleus (India)

Karyomorphology of three species of Haworthia Duval (Xanthorrhoeaceae)

Somatic chromosomes were studied from roots from seven species and two varieties of the genus Opuntia collected from different localities in Eastern India. 2n = 22 chromosomes were observed in four, 2n = 44 in two and 2n = 55 chromosomes in one population. The total chromosome length is maximum in O. Ficus-indica (2n = 55) and minimum in O. microdasys var. lutea (2n = 22). The karyotypes show a similarity in basic number x = 11, except for the horticultural variety, O. monocantha variegata with 2n = 34. The chromosome sizes range from very small (0.97 mm) to medium (3.46 mm); the primary constriction varies from nearly submedian to median and the numbers of chromosomes with secondary constrictions are from four to six. Numerical analysis of data indicates a general similarity of the karyotypes, with O. Ficus-indica occupying a separate position. © 2000 Taylor & Francis Group, LLC.

The use of multivariate analysis of karyotypesto determine relationships between species of Opuntia (Cactaceae)

Chromosome studies have been carried out on diploid, triploid and tetraploid populations of Costus speciosus distributed in the Eastern Himalayas. Detailed karyotype analysis with suitably modified techniques shows a wide range of structural alterations of chromosomes even within populations of the same ploidy level. Meiotic data reveals 18 bivalents in the tetraploid and varying numbers of bi- and univalents, with rare occurrence of trivalents, in the triploids. These observations suggest the role of allopolyploidy and structural alterations of chromosomes in the evolution of these cytotypes. © 1983, Japan Mendel Society, International Society of Cytology. All rights reserved.

CYTOLOGIA

Genetic Diversity in Costus speciosus (Koen.) Sm

Evidences showing that chromosomes in eukaryota, with their complex organization, exhibit dynamism in structure and behaviour for controlling differentiation, variability and reproduction have been reviewed. An outline has been given of the stepwise evolution of the functionally differentiated chromosome segments and their chemical make up including protein components and sequence complexity of DNA. The outline includes the origin of chromosomal control of metabolism in extranuclear organelles. During organogenesis, the chromosomes, maintaining the basic genetic skeleton, undergo variation in structure and chemical components, thus exhibiting dynamism. Addition, loss and inactivation of heterochromatic segments have been correlated with adaptation and alteration in chromosome size. Data on the possible role of repeated sequences in control and integration have been presented. Endomitotic replication of the chromosome, in place of normal mitosis, during differentiation is an example of dynamic behaviour, adapted to meet the need of uninterrupted transcription during differentiation without increasing the number of cells. The predetermined symmetrical growth of the organism is thus maintained. In several asexually reproducing species, dynamism is manifested in genetically controlled unusual behaviour of chromosomes, where the somatic tissue often represents a chromosome mosaic. It has been adapted to meet the need of generating variability and genotypes through bud mutation in the absence of effective sexual reproduction. Data in favour of the concept of dynamism indicate that evolution of eukaryotic chromosome has involved progressive complexity of chromosome structure on the one hand, and flexibility in its behaviour and structure, maintaining the basic genetic make up, on the other. It has enabled the chromosomes to exert supreme control on all aspects of metabolism which are sequential and phasic in higher organisms. © 1978 Indian Academy of Sciences.

Proceedings of the Indian Academy of Sciences - Section B. Part 3, Plant Sciences

Change in chromosome concept

From the study of somatic chromosomes of Dracaena metallica Hort., which shows a high degree of variation in chromosome number, and which is propagated exclusively by vegetative means, it is clear that the chromosome numbers have got some common characteristics in all the offshoots. Counting of a large number of plates in the root tips of different offshoots shows the repetition of almost similar types of chromosome numbers which tend to remain as multiples of 7. In spite of this homogeneity in the offshoots, differences in the tendencies of variation were noticed, particularly in the occurrence of the most frequent chromosome numbers. In the long run, such differences may lead to the production of new species having distinct chromosome complements. © 1971 Taylor & Francis Group, LLC.

Variation in chromosome number and its role in speciation in dracaena metallica hort

1. A cytological investigation of five different species and varieties of the genus Mentha have been carried out. Their chromosome numbers noted here are as follows: i) Mentha viridis Linn. var. I 2n=32 ii) Mentha viridis Linn. var. II 2n=48 iii) M. piperita Linn. var. I 2n=72 iv) M. piperita Linn. var. II n=66 v) M. arvensis Linn. 2n=90 2. Karyotype analysis in detail has been performed in four species and varieties. Meiosis has been worked out in M. viridis var. I and M. piperita var. II. 3. It has been shown that each species and variety has got a karyotype, characteristic of its own. This fact indicates that evolution has been associated with a considerable degree of structural changes of chromosomes in them. 4. Role of polyploidy in speciation in this genus has been emphasized in view of the present and the previous data available on this aspect in the different species. Six has been considered as the possible basic number of chromosomes, from which all the euploid and aneuploid series have evolved. 5. Early literature as well as the present records show that in species of this genus, a large number of chromosomal biotypes occur. The importance of analysis of these biotypes from a cyto-ecological standpoint has been emphasized. 6. Variation in chromosome number in the same somatic tissue and the ineffective method of sexual reproduction have been pointed out as responsible for the origin of chromosomal biotypes or individuals with different chromosome numbers. Their role in speciation as an additional means is obvious. In conclusion, the authors wish to express their sincere thanks to Dr. K. P. Biswas, Director in charge, Medicinal Plants Scheme, Government of West Bengal, for giving us all facilities to collect different wild and cultivated species of Mentha at Rongo, Darjeeling. © 1959, Japan Mendel Society, International Society of Cytology. All rights reserved.

Cytological Studies on Different Species of Mentha with Special Reference to the Occurrence of Chromosomal Biotypes

Genetica

An investigation on the karyotype of the genus Crinum and its phylogeny

1. The present report deals with the somatic study on nine different species, namely, Hymenocallis daphne, Hymenocallis harrisiana, Hymenocallis littoralis Salisb., Hymenocallis rotata Salisb., Hymenocallis concinna, Hymenocallis senegambica Kunth & Bouche, Pancratium zeylanicum Linn., Haemanthus kalbreyeri Baker, Cooperanthes percyi Lanc. 2. Refined techniques involving the use of aesculin and coumarin have been adopted for the karyotype analysis and numerical study of chromosomes of different species investigated. 3. In addition to the presence of normal number in the somatic cells, considerable variation has been observed in the same root-tip tissue, which ranges from as low as eleven to ninety-two. 4. A discussion on the systematic position of the different genera has been made and on the basis of the present cytological data, the classification of Hutchinson is being confirmed. 5. Each genus is characterized by mostly having a constant chromosome number in all its species. Evolution within the genus, in view of the karyotype differences, has been visualized to have been brought about mainly through structural changes of chromosomes and also polyploidy. 6. In view of the chromosome number as well as their general morphology, the three genera Crinum, Pancratium and Hymenocallis have been considered to be much related, their position in the evolutionary scale being assigned as Crinum-Pancratium-Hymenocallis. 7. The significance of structural and numerical alteration of chromosomes within the same somatic tissue has been discussed, and their role in speciation in vegetatively propagated plants has been pointed out. It has been further emphasized that the balances within the tissue in such cases are maintained by the constant ratio involving the absolute amount of chromatin matter and the total amount of cytoplasm present in the tissue as a whole. 8. Discrepancies in the report of the genus Haemanthus by Satô have been considered to be due to structural alteration in chromosomes, observed in the present case within the somatic tissue. 9. An investigation on the hybrid nature of Cooperanthes, claimed to be a hybrid between Cooperia and Zephyranthes, has been carried out, but it has been emphasized that far more convincing data should be forthcoming for establishing its status as a hybrid. © 1956, Japan Mendel Society, International Society of Cytology. All rights reserved.

Journal	Caryologia
Publisher	-
ISSN	0008-7114
Open Access	Yes