Cytogenetic Studies on Talinum and Portulaca

Abstract

The chromosome number of 9 spp. and vars. of Talinum and 7 spp. of Portulaca are listed, illustrated, and discussed in relation to evolutionary trends. The Talinum spp. counted form a polyploid series ranging from n[long dash]12 to n = 36. Cortical root-tip areas of T. parvi-florum frequently have cells with n = 48, but this condition was not found in the other spp. The portulacas investigated do not form a regular polyploid series. Their chromosomes differ markedly in size, are larger than those of Talinum and range in number from n = 4 to n = 27. Attempts at interspecific crossing within the 2 genera were failures and no records of such crosses were found in the literature. One species each, of Talinum and Portulaca, are mentioned, which appear to be new spp. Talinum paniculatum var. variegata is regarded as a horticultural form but the author considers its morph. features and chromosome number (n = 36 as contrasted with T. paniculatum, in which n = 12) warrant regarding it as a separate species.