Chromosome Number in Cynodon dactylon in Relation to Ecological Conditions

Populations of Cynodon dactylon (L.) Pers. were collected from three habitat types (roadsides, lawns and paddy-fields) within each of five climatic regions (arid, dry, intermediate, wet and hill country) in Sri Lanka. Further populations were collected from forests and grasslands in the hill country. Most populations contained only tetraploid plants (2n = 36), but populations from roadsides and lawns in the wet region, and from forests in the hill country, contained only diploid plants (2n = 18). Populations from paddy-fields in the wet region contained both tetraploid and diploid plants. No triploid plants were found in any environment, despite the fact that C. dactylon predominantly reproduces vegetatively by both stolons and rhizomes. Soil acidity seems to be the main factor determining the distribution of the two cytotypes.