石山苣苔属四种( 含一变种) 植物的 染色体数目和倍性研究.

Petrocodon Hance (Gesneriaceae) consists of 41 species and is mainly distributed in the limestone region of South China. So far? the chromosome numbers of only four species have been reported, with the rest species in the genus remained uninvestigated yet. Furthermore, the evolutionary history of the chromosome number and ploidy in Petrocodon as well as in its sister genus Primulina remain unexplored, and particularly whether it affected their diversifications into extant species diversity remain unknown. In this study, the root tip cells of four species (including one variety) of Petrocodon (i.e. Petrocodon dealbatus var. dealbatus. Petrocodon dealbatus var. denticulatus. Petrocodon longangensis and Petrocodon sp.) which were generated by hydroponic culture method for the cutting leaves? were used for the chromosome experiments. First, the effects of various experimental treating conditions on the quality of chromosome squashing were explored and the chromosome numbers were counted. Then the evolutionary history of chromosome numbers in Petrocodon and Primulina were traced based on the molecular phylogenetic tree, and whether the diversifications of the species diversity for the two genera were impacted by changes of the chromosome number or especially the ploidy or not was discussed. The results were as follows: (1) The root tip of 1- 1.5 cm length, pretreatment for 5 h with 0. 002 mol.L-18-hydroxyquinoline solution and dissociation for 4 min was a suitable chromosome preparation condition. (2) All the four species (including one variety) investigated were diploid and the chromosome numbers were the same (2n = 2x = 36). (3) Although the reconstruction of the ancestral state of the chromosome number of Petrocodon and Primulina failed to give any resolution for the most recent common ancestors of the two genera (generic stem node) and each of the genera (generic crown nodes), the chromosome number of Petrocodon and Primulina was highly conserved with most taxa possessing 2n = 2x = 36, except for the ploidy or chromosome number changes in few species? suggesting the disproportional diversification of species diversity between Petrocodon and Primulina was not correlated to the change of the chromosome number or ploidy. This study provides a reference for the chromosome preparation of Petrocodon and its allies, and also provides basic data and implications for further research on the classification? systematic evolution and speciation of Petrocodon. [ABSTRACT FROM AUTHOR]