Cytotaxonomic studies on South Indian Loranthaceae.

Abstract

Loranthaceae, chiefly a tropical family, extend into the temperate zones of both hemi spheres. They include parasitic herbs, shrubs and rarely trees. There have been many nomencla tural changes and the taxonomy of the family is somewhat confusing. De Candolle (1830) divided the family into two groups, on the basis of the presence or absence of calyculus, which were treated by most systematists as subfamilies, Loranthoideae with calyculus and Viscoideae lacking calyculus. In more recent classifications, they have been raised to the status of separate families, Loranthaceae and Viscaceae respectively (Barlow 1964, Dahlgren 1977). There is also disagreement with regard to the delimitation of tribes and genera. The classification of Danser (1929, 1933) is now widely followed. The family has been of interest as some species cause considerable damages to timber trees and fruit crops. Despite the large number and wide distribution of species, very little is known on the cyto logy of the Loranthaceae. Chromosome numbers are known in about 73 species of 24 genera mostly from meiotic studies. The most important contributions to the cytology of the family are those of Barlow (1963, 1964) who made extensive cytotaxonomical studies of Australian species. Chromosome numbers of a few species have been determined by Bhaumic (1971), Bir et al. (1980, 1982), Wiens (1964) and others. In the present study detailed investigations of meiosis in 14 taxa (13 species) coming under 7 genera have been made. Seven of these are new counts and in two others the numbers observed here differ from previous reports.

Mitotic karyotype stability and meiotic irregularities in the families Loranthaceae Juss. and Viscaceae Miq

“…A tetravalent ring observed in Struthanthus syringifolius indicates that heterozygosity for chromosomal interchange is also occurring. Similar alterations were reported by Hunziker and Perez-Moreau (1961), Bir et al (1980Bir et al ( , 1984, and Soman and Ramachandran (1987). The latter authors observed a 42 % rate of meiotic irregularity and pollen sterility in Helicanthes elastica.…”

Temperature Sensitive Cytomixis in Helicanthes elastica (Desr.) Dans. (Loranthaceae).

“…During the course of meiotic studies on South Indian members of Loranthaceae a high degree of meiotic irregularities and pollen sterility (42%) was noticed in Helicanthes elastica collected from Ernakulam while the members of this species from Trivandrum exhibited normal meiotic behaviour (Soman and Ramachandran 1987) . On detailed investigation it has been found that these differences in meiotic behaviour in these two population were due to the dif ference in the atmospheric temperature.…”