Abstract: This paper is a cytological part of biosystematic studies on Adenophora Fisch. in Heilongjiang, China. Chromosomal numbers and karyotypes of 10 spp. and 1 var. are reported. The results are summarized in Table 1. The chromosomal numbers and karyotypes of 6 spp. and 1 var. are first reported, including tetraploid species (2n=68) (A. pereskiifolia var. alternifolia, A. amurica and A. gmelinii). The basic number of chromosomes in the genus is mainly 17 (x=17), but that of A. trachelioides and A. remotiflora (2n=36) is 18 (x=18), an unique one in the genus. The karyotypes of all the species examined are relatively uniform, which means that they are derived from a common ancestral type. The chromosomes are smaller, varying between 2-4 μm. The majority of chromosomes are m and sm ones. And a pair of sat-chromosomes and a pair of st chromosomes are always present. The centromeric terminalization value of chromosomes is 57.5-61.9%, showing higher symmetry of karyotypes in the genus. The karyotype of A. tetraphylla (2n=34) is the most symmetrical among these species. Based on its morphological characters and distribution, the species may be considered as a relatively primitive member of the genus. The results show two revolutionary trends in karyotypes of the genus: number variation (including polyploidy and aneuploidy) and structural variation. The polyploidy is one of the principal patterns of speciation in the genus. Combined with the other characters, these species are taxonomically discussed, and two new taxa (A. amurica Fu et Liu and A. pereskiifolia ssp. alternifolia (Fuh ex Y. Z. Zhao) Fu et Liu) are confirmed. A. trachelioides and A. remotiflora (both 2n=36) with obvious petioles seems more advanced than the other species (2n 34).

Key words: Adenopora, Chromosomal number, Karyotype, Heilongjiang