New evidence from the ultrastructural and micromorphological fields in angiosperm classification

Abstract

Based on TEM investigations of some 1850 species and SEM examinations of about 6000 species of the Angiospermae, this is a survey of ultrastructural and micromorphological data (excluding pollen wall characters) which contribute valuable information for the classification of angiosperms. TEM characters predominately relate to phloem features, such as sieve–element plastids and crystalline P–protein, and to those equally present in other tissues, e.g. nuclear protein crystals and dilated ER–cisternae (DC). Of these, the sieve–element plastids with their types and subtypes (S, PI–PVI) and their over 20 forms represent the most thoroughly investigated TEM character. SEM characters mainly relate to epidermal surface features and can be grouped into four categories: (1) Cellular arrangement or cellular pattern; (2) Shape of cells (the “primary sculpture” of a surface); (3) Relief of outer cell walls (“the secondary sculpture” superimposed on the primary sculpture), caused mainly by cuticular striations and superficially visible wall inclusions and wall thickenings; (4) Epicuticular secretions (the “tertiary sculpture” superimposed on the secondary sculpture), i.e. mainly waxes and related substances.Ultrastructural evidence from sieve–element plastids for the classification of Mag–noliiflorae, Caryophylliflorae, Fabiflorae and the unity of the Monocotyledoneae is discussed, while further plastid data are listed for single families (e.g. Buxaceae, Cyrillaceae, Erythroxylaceae, Eucryphiaceae, Gunneraceae, Rhizophoraceae, Vitaceae). Crystalline P–protein dominates in Malviflorae, Violiflorae and Fabiflorae. Nuclear protein crystals are a specific feature of sieve elements of Boraginaceae. DC characterize Capparales s.lat.Micromorphological evidence derived from specific trichomes is presented as an aid to the characterization of Urticales and Loasales, while a detailed analysis of the micromorphology of the seed coat of Cactaceae and Orchidaceae provided new information for the classification of these families at the tribal and generic levels. As a completely new systematic feature for the classification of the Monocotyledoneae first results of micromorphological differences in wax crystalloids and their orientation patterns are presented: The Liliiflorae s. str. are clearly separated against the Zingiberiflorae–Commeliniflorae (incl. Velloziales, Bromeliales, Typhales) and Areciflorae, both characterized by two mutually exclusive and very specific wax types and delimited against taxa with unspecific waxes in the rest of the monocotyledons and all dicotyledons.