The common onion (Allium cepa) is an excellent plant for the assay of chromosome aberrations after chemical treatment. Other species of allium (A. cepa var. proliferum, A. carinatum, A. fistulosum and A. sativum) have also been used but to a much lesser extent. Protocols have been given for using root tips from either bulbs or seeds of Allium cepa to study the cytological end-points, such as chromosome breaks and exchanges, which follow the testing of chemicals in somatic cells. It is considered that both mitotic and meiotic end-points should be used to a greater extent in assaying the cytogenetic effects of a chemical. From a literature survey, 148 chemicals are tabulated that have been assayed in 164 Allium tests for the clastogenic effect. Of the 164 assays which have been carried out, 75 are reported as giving a positive reaction (i.e., causing chromosome aberrations), 49 positive and with a dose response, 1 positive and temperature-related, 9 borderline positive, and 30 negative; 76% of the chemicals gave a definite positive response. It is proposed that the Allium test be included among those tests routinely used for assessing chromosomal damage induced by chemicals.

Chromosome aberration assays in Allium. A report of the U.S. Environmental Protection Agency Gene-Tox Program.

The amplified fragment length polymorphism (AFLP) method was used to evaluate genetic diversity and to assess genetic relationships within the section Mentha in order to clarify the taxonomy of several interspecific mint hybrids with molecular markers. To this end, genetic diversity of 62 Mentha accessions from different geographic origins, representing five species and three hybrids, was assessed. Three EcoRI/MseI AFLP primer combinations generated an average of 40 AFLP markers per primer combination, ranging in size from 50 to 500 base pairs (bp). The percentage of markers polymorphic ranged from 50% to 60% across all accessions studied. According to phenetic and cladistic analysis, the 62 mint accessions were grouped into two major clusters. Principal coordinates analysis separated species into well-defined groups, and clear relationships between species and hybrids could be described. Our AFLP analysis supports taxonomic classification established among Mentha species by conventional (morphological, cytological, and chemical) methods. It allows the assessment of phenetic relationships between species and the hybrids M. spicata and M. × piperita, largely cultivated all over the world for their menthol source, and provides new insights into the subdivision of M. spicata, based for the first time on molecular markers.

Hybridization in the section Mentha (Lamiaceae) inferred from AFLP markers

Chromosome numbers in the genus Mentha L.

Complex geographical distribution patterns and agamospermy have united to obscure systematic relationships in the genusErigeron (400+ species) Sequence data were analyzed from the internal transcribed spacer region of nrDNA (ITS) and 58S cistron for 77 taxa including 63Erigeron species Results support the North American origin ofErigeron and document thatAphanostephus, Conyza, and three small genera restricted to South America (Apopyros, Hysterionica, Neja) are all derived from withinErigeron Phylogenetic data indicate that agamospermy has arisen at least three times inErigeron and that autogamy has evolved independently inConyza and inE sectTrimorpha

Biogeographical and evolutionary insights on Erigeron and allies (Asteraceae) from ITS sequence data

Sesuvium portulacastrum (L.) L. (sea purslane, cenicilla) is a pantropical, perennial, trailing herb (Aizoaceae) with pink-purple or occasionally white flowers that grows on coastal beaches of five continents and many islands. Herein we present a review of the biology of S. portulacastrum. It is an important pioneer species on sandy beaches in the subtropics and tropics, where its stoloniferous, mat-forming growth habit promotes embryonic dune formation in belts parallel to the shoreline. Colonies act as barriers to intercept and hold water and wind transported sand. Sesuvium portulacastrum's success as a colonizing species is related, in large part, to its ability to be propagated by vegetative fragments and the tolerance of these fragments to salt water. Indeed, it has apparently reached nearly all locations in which it occurs by drifting segments in the sea. Other factors contributing to its success as a pioneer species include its tolerance of salt spray, sand scouring and burial, high substrate temperatures and low levels of soil nutrients. Its northern and southern distribution limits appear to be limited by the frequency, duration and severity of freezing temperatures.

/pdf/the-biological-flora-of-coastal-dunes-and-wetlands-sesuvium-1xga4qrig1.pdf

The Biological Flora of Coastal Dunes and Wetlands. Sesuvium portulacastrum (L.) L.

Further investigations on several genera of Umbelliferae and their interrelationships

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=32ii) Mentha viridis Linn. var. II 2n=48iii) M. piperita Linn. var. I 2n=72iv) M. piperita Linn. var. II n=66v) M. arvensis Linn. 2n=902. 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.

https://www.jstage.jst.go.jp/article/cytologia1929/24/2/24_2_198/_pdf

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

The importance of the cytological s tudy in tracing the systematic positions and affinities of the different species of a genus has been amply demonstrated in recent years (Vide GUNDERSEN, 1950; TISCI~5ER, 1956). Such investigations have helped to classify and solve a number of disputed problems of taxonomy. In addition to indicating the affinities and the phylogenetic positions of the different genera, such studies further provide clues to the problem of evolutionary tendency exhibited by the different taxonomic units. In India, a number of species of Piper grows in abundance and various species are cultivated also for their use as spices. They are mainly tropical in distribution. The other allied genus Peperomia is also represented by a number of species in India. These two genera are the main constituents of the family Piperaceae. No detailed cytological work has been carried out yet on the species growing as wild and in cultivation in India. Of the few species growing in India, the cytological data of which are available, mainly the chromosome numbers are reported (JOHNSON, 1910 ; 1914 ; ABELE, 1923 ; JOHANSEN, 1931 ; JANAKI AM~AL, I945 ; TJIO, 1948 and vide DaRLINGTON and WYLIE, 1955).

Chromosome studies on two genera of the family piperaceae

1. Properties of paradichlorobenzene in causing fragmentation of chromosomes have been worked out after trials in different species of Monocotyledons as well as of Dicotyledons. Six species under Dicotyledons and ten species under Monocotyledons were used for the purpose.2. Different species require different periods of treatment in the chemical for the breakage of their chromosomes. Dicotyledons, generally, require longer periods than the Monocotyledons.3. The results of recovery experiments have been discussed and the potentiality of the chemical for mutagenic purposes has been pointed out.4. In fixation schedules for chromosome analysis, a cautious application of the chemical is recommended, because if the period of treatment is prolonged over the one required, fragmentation of the chromosomes may result.

Chromosome Breakage Through Paradichlorobenzene Treatment

RIASSUNTOE studiato il cartogramma di alcune specie di Portulacaceae: Portulaca quadrifida L. (2n = 36), Portulaca oleracea L. (2n = 45), Portulaca grandiflora Hook. var. a fiore semplice (2n = 18), Portulaca grandiflora Hook. var. a fiore doppio (2n = 18), Portulaca sp. (2n = 18). E pure studiato il cartogramma di alcune Aizoaceae: Sesuvium portulacastrum L. (2n = 36), Trianthema monogyna L. (2n = 26), Mollugo hirta Thunb. (2n = 36).Oltre la morfologia cromosomica e stata studiata anche la meiosi di alcune delle suddette specie.Appare evidente il ruolo della poliploidia nella speciazione delle due famiglie per le specie a piu alto numero di cromosomi, e l'importanza della condizione poliploide per la tolleranza a condizioni ecologiche difficili. La morfologia cromosomica conferma l'affinita delle due famiglie considerate.

https://www.tandfonline.com/doi/pdf/10.1080/00087114.1956.10797565

Nripendra Kumar Bhattacharyya

Papers

Further investigations on several genera of Umbelliferae and their interrelationships

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

Chromosome studies on two genera of the family piperaceae

Chromosome Breakage Through Paradichlorobenzene Treatment

Cytogenetics of Some Members of Portulacaceae and Related Families