Pollen morphology of selected taxa of Ehretiaceae from Western Ghats, India.

Abstract

Pollen Morphology is an important tool in the identification of a genera. Data on pollen morphology is used as a reference in other fields of palynology like allergic studies, melissopalynology, tracing the history of vegetation, genetic and evolutionary studies, climate change studies etc. Pollen morphology of two genera of Ehretiaceae family is studied using Scanning electron microscope. Palynological contributions are still fragmentary in the family Ehretiaceae of southern India. Ehretia pubescens Benth is a small tree belonging to Ehretiaceae family located at the foothill of Chamundi hill reserve forest which is a part of Western ghat near Mysuru and Cormona retusa (Vahl) Masam is a shrub found 3400ft above on top of Chamundi Hill. Pollen grains were acetolyzed and Scanning Electron Microscopic studies conducted to obtain data on pollen morphology. The study is conducted to assess the taxonomic significance of pollen morphology in relation to their phylogenetic origin of the two genera of Ehretiaceae in the region. The palynological evidence shows Ehretia pubescens with tri-zonocolporate and heterocolpate pollen grains and Cormona retusa with tricolpate pollen grain without the pseudocolpi. Both genera have foveolate tectum. Palynological data indicate that these two naturalized taxa ie. Ehretia pubescens and Cormona retusa belong to two different lineage of Ehretia and can be identified by their pollen morphology. Diversity in the pollen characters points towards the eurypalynous nature in Ehretiaceae.