Systematic significance and pharmaceutical potentials of trichomes in accessions of Sesamum indicum L. Pedaliaceae

Abstract

Fresh leaves of twelve accessions of Sesamum indicum were collected after 12 weeks of planting and morphological-histology of trichomes were studied. These features may be used for the delimitation and determination of pharmaceutical potentials of the accessions. These accessions were found to exhibit high degree of heterogeneity in their trichome features. Nine types of trichomes were observed: unicellular, glandular peltate, capitate glandular, long unbranched uniseriate, short unbranched uniseriate, scale, multicellular, multiseriate capitate glandular and branched uniseriate trichomes. Lale-duk recorded the highest number (six types), four in accessions Ex-Sudan, Adaw-ting (Improved) and Ex-Gombe 1, three in accessions Ex-Gombe 3, Ex-Gombe 4, Ex-Gombe 5 and Ex-Gombe 6, two in kenana 4, Adaw-wula and Adaw-ting. The most frequent trichome type is short-unbranched uniseriate (76.52%), followed by long-unbranched uniseriate (72.73% and scale (65.11%). The least frequent was multiseriate capitate glandular (11.5%). The density of trichomes varied from accession to accession. Trichome density was the highest in Ex-Gombe 3 (63.2±0.49 mm 2) and the lowest was recorded by Ex-Gombe 4 (4.40±0.29 mm 2). The high variation in density coupled with the presence of glandular trichomes suggest that all the parts of these accessions probably contain or secrete chemicals that have many uses in the pesticide, pharmaceutical and flavour/fragrance industries and to conserve water. Furthermore, the trichome features varied from accession to accession; hence, are found to be good diagnostic and additional tool in identification as well as nomenclature of the accessions of S. indicum.