Leaf Peltate Glandular Trichomes of<i>Vernonia galamensis</i>ssp.<i>galamensis</i>var.<i>ethiopica</i>Gilbert: Development, Ultrastructure, and Chemical Composition

Abstract

Plants from the genus Vernonia produce a variety of flavonoids and bitter sesquiterpene lactones important for agriculture and human health. Leaf glandular trichomes of Vernonia galamensis ssp. galamensis var. ethiopica Gilbert (VGAE) were investigated for ultrastructural development and content composition because sesquiterpene lactones that impart a bitter taste to the leaves have been associated with the presence of these glands. Trichome ultrastructure was examined using LM, SEM, and TEM. Glands were removed from the leaf surface, and the chemical composition of gland contents was determined using HPLC and high‐resolution mass spectrometry. Immature and mature 10‐celled peltate biseriate glandular trichomes were present only at the abaxial side of the leaf. A large subcuticular space (head) developed from the most distal cell pair of the mature trichome and gradually filled with an osmiophillic substance. Mass spectrometry analysis revealed that the peltate trichome is a major source of prevernocistifolide‐8‐O‐isobutyrate. This glaucolide‐type sesquiterpene lactone was previously identified as a major constituent of the aerial parts of VGAE.