Cytological Study as an Aid in the Interpretation of the Systematic Status of the Different Genera of Araliaceae

Sharma, Arun Kumar; Chatterji, A. K.

doi:10.1508/cytologia.29.1

Cited by 10 publications

(5 citation statements)

References 2 publications

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“…Within the Polyscias-Pseudopanax clade, Pseudopanax and Tetraplasandra are tetraploids. Most species of Polyscias have 2n = 24, although occasional polyploids have been reported in P. scutellaria (with 2n = 24 or 48; Guha, 1971) and P. guilfoylei (2n = 24 or 36; Sharma & Chatterji, 1964). Below, we discuss chromosomal variation in those genera for which sufficient data are available.…”

Section: Discussionmentioning

confidence: 98%

“…Hedera is an exception, with many polyploid taxa ranging from 2n = 48 to 2n = 192 (Vargas & al., 1999). Most workers have hypothesized a basic chromosome number in the family of x = 12 (Sharma & Chatterji, 1964;Raven, 1975;Lowry, 1986). However, two species (Polyscias guilfoylei and Schefflera elegantissima) have reports of 2n = 36.…”

Section: Discussionmentioning

confidence: 99%

“…A. racemosa L. II 24 Sharma & Chatterji, 1964;Graham, 1966;Löve & Löve, 198236, 48, Guha, 1971 Aralia spinosa L.…”

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Chromosomal evolution in Araliaceae and close relatives

Lowry

Plunkett

et al. 2004

TAXON

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Chromosome numbers of 45 accessions representing 16 genera and 37 species of Araliaceae are herein reported, of which 30 species and seven genera (Apiopetalum, Arthrophyllum, Delarbrea, Merrilliopanax, Metapanax, Myodocarpus, and Pseudosciadium) are recorded for the first time. The evolution of this character is also examined in light of recent hypotheses of phylogenetic relationships. Chromosome numbers in the family are relatively uniform, generally with 2n = 24 or 48. However, the genus Hedera exhibits extreme variability, with a polyploid series ranging from 2n = 48 to 192. The basic number of Araliaceae is inferred to be x = 12, although x = 6 cannot be ruled out. The “Asian palmate” clade, the largest of the three major clades of core Araliaceae, is primarily characterized by polyploidy, although several genera have sometimes been regarded as evolutionarily “primitive”. By contrast, Aralia, Panax, and Polyscias (representing other major clades within the family) include species with both diploids and tetraploids. Four genera recently segregated from core Araliaceae (Apiopetalum, Delarbrea, Myodocarpus, and Pseudosciadium) are reported as n = 12. The formerly apiaceous Hydrocotyle (now placed in Araliaceae) is best interpreted as x = 12, although some aneuploid species may exist with x = 9. Hydrocotyle also exhibits extensive variation in ploidal level. Within Araliaceae, chromosomal variation is largely related to ploidal level, with relatively few cases of aneuploidy, such as those documented in Panax ginseng and Hydrocotyle. The available data are largely consistent with the hypothesis that the basic chromosome number of Apiales is x = 6.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Chromosomal evolution in Araliaceae and close relatives

Lowry

Plunkett

et al. 2004

TAXON

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“…The chromosome number in all the species of the genus should be recorded first, and in some cases needs reconfirmation before suggesting segregation of these taxa based on chromosomal studies. However, x = 12 or x = 6 is regarded as the most plausible basic and ancestral chromosome number in Apiales (Sharma and Chatterji 1964;Yi et al 2004 Pimenov et al 1999). We are of the opinion that the base number x = 11 seems to have been much favoured in the genus.…”

Section: Chromosomal Status and Cytogeographic Patternmentioning

confidence: 99%

Chromosome counts and male meiosis in two species ofPleurospermumHoffm. (Apiaceae): additional comments on the cytogeographic pattern of the genus

2016

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Pleurospermum Hoffm. (Apiaceae), a widely spread, heterogeneous genus of complex and controversial taxonomy, is poorly known for chromosome number and meiotic details from the Indian subcontinent. In the current study, we examined male meiosis, chromosome counts, and pollen fertility in two species, P. candollii and P. govanianum from alpine areas of north-west Indian Himalaya. Both the species exist at diploid level (P. candollii, n = 11 or 2n = 22, P. govanianum, n = 9 or 2n = 18) with two different basic chromosome numbers, x = 9 and 11. Meiotic course in the majority of pollen mother cells (PMCs) is normal; however, few meiocytes showed the occurrence of chromatin transfer among themselves which resulted into the formation of hypoploid and hyperploid PMCs. In addition, some PMCs depicted associated irregularities such as laggards, and chromatin bridges during meiosis-I and II. Microsporogenesis was also observed to be abnormal, and was characterized by the presence of micronuclei in the sporads. Owing to low frequency of meiotic irregularities, pollen fertility was not affected to greater extent; however, variable sized pollen grains were noticed in P. candollii. Analysis of previously published chromosome data revealed that there is no specific cytogeographic pattern formed for the genus on the basis of which we can construct any geographic segregation between the two basic numbers, x = 9 and 11. However, in a broader sense two overlapping zones seems to appear for the two basic numbers in the East, central and south Asia.

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“…These four categories are not sharply distinct, but grade imper ceptibly into each other (Stebbins 1971). The chromosomes are also described as median, nearly median, nearly submedian, submedian, nearly subterminal, sub terminal, nearly terminal and terminal (Sharma and Sharma 1960, Sharma and Choudhury 1964, Adhikary 1963, 1974, Bose and Flory 1965. Thus there exists a great deal of confusion in describing a chromosome on the basis of centromere position.…”

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confidence: 99%

A system of chromosome classification and nomenclature.

Abraham

Prasad

1983

CYTOLOGIA

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Chromosome morphology is usually studied on the basis of the position of the primary constriction (or centromere or kinetochore), which is a principal landmark in contracted metaphase chromosomes. Cytologists have adopted several methods to determine the centromere locations and described the chromosomes as telocentric (centromere at one end of the chromosome), acrocentric (centromere near one end of the chromosome), submetacentric (centromere nearer to one end of the chro mosome than the other) and metacentric (centromere at or near the middle of the chromosome). These four categories are not sharply distinct, but grade imper ceptibly into each other (Stebbins 1971). The chromosomes are also described as median, nearly median, nearly submedian, submedian, nearly subterminal, sub terminal, nearly terminal and terminal (Sharma and Sharma 1960, Sharma and Choudhury 1964, Adhikary 1963, 1974, Bose and Flory 1965. Thus there exists a great deal of confusion in describing a chromosome on the basis of centromere position. Levan et al. (1964) recognised the location of centromere in median point (M), median region (m), submedian region (sm), subterminal region (st), terminal region (t) and terminal point (T). However, this system did not give due consideration to a number of oftquoted nomenclatures of centromere locations like nearly submedian and nearly subterminal. The system of Levan et al. (1964) was based on a) dif ference (d) between long arm (1) and short arm (s), where the whole chromosome =10 units; b) arm ratio (r) as the ratio of short arm/long arm; and c) centromeric index (i) as 100 s/c in the different regions, where c is the total length of the chro mosome. Nevertheless, this system gave biased preference to the short arm of the chromosome in determining the arm ratio and the centromeric index. The criterion of difference (d) between long arm (1) and short arm (s) is not always helpful as evi dent from our study of karyotypes of Aloe barbadensis and Furcraea gigantea (Abraham and Nagendra Prasad 1979, 1980). Recently, Adhikary (1974) proposed a system incorporating all the possible and up-to-date usage of centromere locations with reference to intermediate regions between terminal and median points. He recognised 4 fixed points and 4 inter mediate regions. The fixed points were median (M), terminal (T), submedian (SM) and subterminal (ST). The intermediate regions were nearly median (nm), nearly terminal (nt), nearly submedian (nsm) and nearly subterminal (nst). This system was based on arm ratios, R1 (short arm/long arm) and R2 (long arm/short arm).

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Cytological Study as an Aid in the Interpretation of the Systematic Status of the Different Genera of Araliaceae

Cited by 10 publications

References 2 publications

Chromosomal evolution in Araliaceae and close relatives

Chromosomal evolution in Araliaceae and close relatives

Chromosome counts and male meiosis in two species ofPleurospermumHoffm. (Apiaceae): additional comments on the cytogeographic pattern of the genus

A system of chromosome classification and nomenclature.

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