Systematic Study of the Genus I pomoea L. (Convolvulaceae) of Nepal

Abstract

The genus Ipomoea is a large and complex genus, commonly called by the name ‘Morning glory’, which comprises the largest number of species (ca. 600) within the family Convolvulaceae. The member of Ipomoea is widely distributed throughout the tropics and subtropics with the greatest species diversity occur in the Americas and Africa (Austin, 1997). In Nepal the genus is distributed throughout the Eastern, Central and Western region of the country with altitudinal distribution ranging from 80 to 2400m. Out of ca. 600 species of Ipomoea around the world, 14 species were earlier reported from Nepal by press et al. (2000) with one subspecies. The present study confirmed the presence 15 species (I. alba, I. aquatica, I. batatas, I. cairica, I. eriocarpa, I. hederifolia I. mauritiana, I. muricata, I. indica, I. nil, I. obscura, I. pes-tigridis, I. purppurea, I. quamoclit and I. triloba) and one subspecies (I. carnea subsp. fistulosa). Among them two species are reported as new record for Nepal, including I. indica and I. triloba. A species which has a character similar with that of I. aquatica is reported as a doubtful species which require further study for confirmation. Presence of these species in Nepal is confirmed by my own collection, thorough examination of all available literatures, herbarium specimens deposited in KATH and TUCH and images available from BM, E and MO from online journal and web-site. Morphological characters are taken as the main basis of this study such as habit, shape and size of the leaves, shape, size and integuments of the sepals, shape and size of the corolla, number of lobes on pistil, integuments of the ovary and fruits etc. Apart from morphology, anatomical (stem and stomata), palynological and cluster analysis have also been carried out. Regarding the phenology, the flowering period of the most of the species is usually in February-October and fruiting period is in October-January. Among the studied species, I. cairica and I. carnea subsp. fistulosa are found to be bloom throughout the year. The identification keys are prepared on the basis of morphological variation found among the species. The stomatal study conclude that the all the species of Ipomoea bear Paracytic or Rubiaceous type of stomata. The considerable variation was found in stomatal frequency, size and number of stomata among the species. For palynoligical study, the new method applied by previous researcher was followed. Pentoporate, spheroidal or globose type of pollen grains with echinate exine pattern are found in all species of Ipomoea. Some nomenclatural changes have been observed during study. The name I. carnea Jacq. is changed in to I. carnea Jacq. subsp. fistulosa (Mart. ex Choisy) D. F. Austin. Similarly species I. turbinata Lag. is now known as I. muricata (L.) Jacq. Taxonomic study of the plant is very important for the country to innumerate the flora of that country, which helps to find out not only the status of plant diversity but also the economic important, status, history and distribution of plant taxa of that country. The author believes that present study helps to document and make better understanding about the genus Ipomoea of Nepal because there was no such kind of study was done previously in Nepal. The study was carried out in very short period of time therefore, the work on this genus should be continue in future for enumerating the whole species Ipomoea found in our country. It also helps to update the checklist and play a significant role in the preparation of Flora of Nepal.