Cytological Study Of Some Important Liverworts And Index To Bryophyte Chromosome Counts Update

Bryophytes,an important group in plant kingdom,are widely distributed. Bryophytes not only have gametophytes,which live independently and have both stem and leaves,but also have sporophytes with complicated structure which parasitizes gametophytes.Chromosomes are the carrier of genes.Chromosome number and karyotype are the ground work of taxonomy,cytology and genetics. Cytological studies on bryophytes can provide the informative data for systematics and cytology,and can reveal the karyological variability in bryophytes.Moreover, karyological data also can shed light on the taxonomic and phylogenic problems of bryophytes.However,contrast to flowering plants,primary constriction and secondary constriction of bryophytes are not very clear.The chromosomes of bryophytes are very small.Most bryophytes do not have active mitosis meristematic tissue.All these make cytological study of bryophytes very difficult.Many cytological problems of bryophytes are unsettled.Materials used for this experiment were collected from Zhejiang,Fujian,Sichuan,Jilin Provinces in China and Singapore.We used improved methods and studied 14 species of liverworts which belong to 10 genera in seven families.The chromosome number of three species (Acrolejeunea pycnoclada(Taylor) Schiffn.,Archilejeunea planiuscula(Mitt.) Steph., Schiffneriolejeunea pulopenangensis(Gottsche)Gradst.) is reported for the first time, that of five species(Jungermannia atrobrunnea Amakawa,Lejeunea anisophylla Mont.,Plagiochila parvifolia Lindenb.,Ptilidium ciliare(L.)Hamp,Radula japonica Gottsche ex Steph.) is newly reported in China.In the research,karyotypes of 14 liverworts are also investigated.The results show that the chromosome numbers are relatively conservative,usually n=8 or n=9.However,the karyotypes,the chromosome size,position of centromere and value of the biggest chromosome/the smallest chromosome reveal that the karyotype is diverse and the structure of chromosomes are variable.The knowledge of the differences of chromosomes among different groups of bryophytes is valuable for the study of taxonomy and evolutionary biology.The last worldwide index to chromosome counts of bryophytes "Index to bryophyte chromosome counts" was published by Fritsch(1991).It has been one of the most valuable references for cytological research of bryophytes.This index promoted the cytological research in bryophytes.That old index,however,has not been updated for 18 years.It is thus necessary to present an additional updated index to bryophyte chromosome counts in the world.The present paper provides an updated version.We also input the brandnew data into the chromosome database which was built previously in our laboratory,and a new version of chromosome database is presented.