Glandular Trichomes on the Leaves of Nicotiana tabacum: Morphology, Developmental Ultrastructure, and Secondary Metabolites

Abstract

Glandular trichomes found on the surface of many higher plants contain specialized cells that produce and secrete copious amounts of particular secretory products. Leaf glandular trichomes of the non-model plant species Nicotiana tabacum represent a biologically active and stress-responsive tissue that contributes to plant defense response against biotic and abiotic stress and also influences leaf aroma and smoke flavor. Two morphologically different types of tobacco capitate trichomes, long- and short-stalked, with distinct functions, display ultrastructural features that are common to terpene-secreting glands, but only the secretory cells of the tall glandular trichomes are considered to be the site of biosynthesis of certain exudate compounds, including diterpenes and sucrose esters. Ultrastructural and histochemical characterization of tall glandular trichomes is described in an attempt to understand the contribution of these glands to the total secretion produced. Possible roles of distinct cellular compartments involved in the secretory process and secondary metabolite secretion under in vitro conditions are discussed.