Inconstancy in Chromosome Number in Some Species of Cassia L. Found in Nepal
AbstractChromosome count of five species of the genus Cassia L. (sensu lato, s.1.) viz. C. nairobensis Hort. and taxa of sensu stricto (s.s.) like C. mirnosoides L. (Chamaecrista mimosoides (L.) E. Greene, s.s.), C.floribunda Cav. (Senna septemtrionalis H. Irwin & Barneby, s.s.), C. occidentalis L. (Senna occidentalis (L.) Link., s.s.) and C. tora L. (Senna tora (L.) Roxb., s.s.) was carried out. Inconstancy in somatic chromosome number of the species was recorded. The dominant frequency of diploid chromosome number of C. floribunda was 2n =14, the variation in chromosome number ranging from 2n =14 to 26. Similarly, 2n = 18 for C. mimosoides (varying from 14 to 30), 2n = 20 for C. nairobensis (varying from 16 to 28), 2n = 26 and 28 for C. occidentalis (varying from 16 to 38) and 2n = 22 for C. tora (variations, 2n = 16 to 38) were observed.The chromosome number of C. nairobensis Hort. is reported here for the first time. The inconstancy of chromosome number with the instability of heteromorphic nature of chromosome depicts the chromosomal numerical polymorphism in the taxa. The numerical polymorphism of the chromosomes seems to be the factor responsible for the evolution of Linnaean genus Cassia L. s.1. and its complex (Cassia, s.s. Chamaecrista & Senna) formation.
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