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Recent literature criticized the use of the symbol “x” to denote basic chromosome number in cytotaxonomy. I show here that this criticism is superfluous and is based on historical confusion between the concepts of basic chromosome number (or monoploid chromosome number), which is objective, and ancestral basic chromosome number, which is always inferred, by means of several – more or less reliable – methods. The most relevant literature is discussed and, in the end, I propose the use ofxfor basic chromosome number andpfor (hypothetical) ancestral basic chromosome number. [ABSTRACT FROM PUBLISHER]

The present study is part of our research project on cytomorphology of gamopetalous flora of Kashmir Himalaya, a zone with rich biodiversity. Out of 134 species of Gamopetalae meiotically investigated, chromosome numbers for 30 accessions belonging to 17 species and six families are new or varied reports. Euphrasia paucifolia ( n = 22), Lactuca decipiens ( n = 8), Saussurea albescens ( n = 17), Saussurea roylei ( n = 16), Saussurea taraxacifolia ( n = 16) and Veronica deltigera ( n = 8) are first cytological reports for these species. Anaphalis nepalensis ( n = 28), Codonopsis rotundifolia ( n = 16) and Hieracium vulgatum ( n = 27) are new euploid chromosome reports for these species suggesting potential speciation through chromosomal evolution. Besides, Androsace mucronifolia ( n = 10), A. sempervivoides ( n = 10), Cicerbita lessertiana ( n = 8), Dracocephalum nutans ( n = 5), Erigeron patentisquama ( n = 9), Galium pauciflorum ( n = 11), Onopordum acanthium ( n = 17) and Xanthium spinosum ( n = 8) are the first chromosome reports to Indian accessions of the species. Out of the 17 species, 9 species (52.9 %) viz. A. nepalensis, C. lessertiana, C. rotundifolia, D. nutans, E. patentisquama, Euphrasia paucifolia, L. decipiens, O. acanthium and V. deltigera show abnormal meiosis/microsporogenesis of one or other type, thereby leading to pollen anomalies. [ABSTRACT FROM AUTHOR]

The chromosome numbers of forty-one Brazilian species belonging to 11 genera of preferentially terrestrial orchids (subfamilies Cypripedioideae, Spiranthoideae, Orchidoideae, and Vanilloideae) were examined. Previous records for these subfamilies were reviewed in order to identify the ancestral chromosome numbers of terrestrial orchids. The variation observed within the subfamilies Spiranthoideae (2n=28, 36, 46, 48 and 92), and Orchidoideae (2n=42, 44, ca. 48, ca. 80, 84, and ca. 168) was similar to that previously reported in the literature. In the subfamily Spiranthoideae, some species of Prescottia (subtribe Prescottiinae) and some genera of Spiranthinae showed a bimodal karyotype with one distinctively large pair of chromosomes. The analysis of chromosome numbers of the genera in subfamilies revealed the predominance of the polyploid series 7, 14, 21, 28, 42 with a dysploid variation of ±1 in each ploidy level. These results suggest that the basic chromosome number of terrestrial orchids is x1=7 for the subfamilies Spiranthoideae and Orchidoideae, as well as other Epidendroid orchids, and that the majority of the genera are composed of palaeopolyploids. [ABSTRACT FROM AUTHOR]

The somatic and gametic chromosomes of the monotypical genus Grahamia ( G. bracteata) have been studied for the first time: 2n = 18, n = 9. The karyotype is symmetrical; of the nine m pairs one has microsatellites. The basic chromosome number x = 9 is considered to be primitive within the family. [ABSTRACT FROM AUTHOR]

Detailed chromosome counts have been made in 61 species, belonging to 33 genera of Rutaceae. 30 of these species are reported here for the first time. For 18 species at least one previous publication gives a chromosome number differing from that reported here. Such discrepancies are, in most cases, due to errors in counting or identification of the material. By critically reviewing the literature on each particular case, it appears possible to eliminate most of the false data. On the basis of the present results, the base number x = 10 is proposed for the genus Ruta. [ABSTRACT FROM AUTHOR]