Ultrastructure and Secretion of Glandular Trichomes of Tobacco Leaves

Abstract

Summary The two types of glandular trichomes occurring on the leaves of Nicotiana tabacum, N. sylvestris and N. rustica were investigated using light, fluorescence and electron microscopy. The long trichomes, which secrete a clear resinous material, contain electron dense inclusions in chloroplasts and in small vacuoles of their head cells, whereas the short ones exhibit such substances in a different type of plastid, in large vacuoles and in the apoplast of their heads. The long type of trichome is numerous in N. tabacum and N. sylvestris but scarce in N. rustica . This latter difference is probably reflected by the composition of the leaf surface gum, which has been shown to contain cembratrienediol in N. tabacum and N. sylvestris but not in N. rustica (H eemann et al. 1983). It is suggested that this diterpene is produced and secreted by the long trichomes since the short ones do not exhibit resinous material on their surfaces. Instead, the short trichomes probably extrude water containing nicotine since this drug can be detected in aqueous droplets forming around the short trichomes under conditions of high atmospheric humidity.