Diversity of foliar trichomes, trichomes basal insertion cells and cells surrounding the basal insertion cells in family asteraceae

Abstract

Foliar trichome morphology, trichome basal insertion cells (TBIC) and cells surrounding trichome insertion basal cells (CSTIBC) on the  leaves of fourteen species of family Asteraceae were investigated by light microscopy. TBIC and CSTIBC are the two novel characters   investigated in this work, in search of unique character states that could improve the taxonomy of the family. Epidermal peels were  made  following standard procedure. Data obtained showed that both non-glandular and glandular trichomes were present, the   glandular was observed in the genus Vernonia only. The non-glandular trichomes were unicellular, bicellular, tricellular and multicellular   uniseriate. Shriveled cells within the multicellular uniseriate cells were common in Emilia sonchifolia and Emilia praertermissa and   occurred sparsely in Ageratum conyzoides. Uniquely pigmented multicellular uniseriate trichomes with apical cells shriveled or   transparent delimits Bidens pilosa from the other species studied. Amoeboid shaped multicellular uniseriate trichomes delimit     Chromolaena odorata from the other species, while Tshaped trichomes (regular and irregular) delimit the genus Vernonia from the other   genera studied. Shape and width of apical cells of the trichomes differentiate Vernonia cinerea from Vernonia amygdalina. Surface  of  trichomes in Aspilia africana, Synedrella nodiflora and Eclipta alba are uniquely papillate and diagnostic for the three species. TIBC  have  varying shapes with different combinations of 1-4 shapes per species. It is noteworthy that the two species of Emilia can be  delimited  from each other based on the shapes of the TIBC on the abaxial epidermis. The number of CSTIBC was observed to be the  same on the  adaxial epidermis of the two species of genus Emilia. Shapes of CSTIBC in the species studied are diverse. Coefficient of  Variation for all  the characters studied showed species with more variation within each character. Novel characters, TIBC and CSTIBC,  were found to be  useful as additional tools in the taxonomy of family Asteraceae.