Cytotaxonomical Studies of South Indian Scrophulariaceae

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The chromosome number of 21 species belonging to 17 genera of Scrophulariaceae from South India has been studied, of which first record of chromosome has been made in Lymnophila heterophylla, Moniera cuneifolia, Ilysanthes tenuifolia, I. oppositifolia, Micrargeria wightii and Sopulia trfda. Chromosome numbers determined in the present study range from 2n=12 to 20=80.
Chromsome numbers determined in the present study and those reported previously in the family (Fedorov 1974) reveal the presence of a continuous series of basic number between n=6 to 84. The commonest basic number in the famly is n=8 and it is assumed to be the original basic number of the family. It appears that aneuploid changes of chromosome numbers produced the basic numbers of n=6, 7, 8, 9, 10, 11, 12, 13 and 14 in the early evolution of the family, after which polyploid and dibasic amphidiploid gave rise to the higher basic numbers (n=17 to n=84) now found in the family.
Karyotypes in the family also show differences in absolute chromosome size indicating changes in nuclear DNA in evolution. The meiotic chromosome number studied in 17 species is in confirmation with the mitotic chromosomes. The presence of mutivalents and quadrivalents along with bivalents and the presence of anaphasic laggards and bridges and triplar anaphases show evidences in support of the aneuploid and polyploid nature of the species.