Christian Puff

Chemotaxonomic studies of rubiaceous plants containing iridoid Glycosides

Abstract Thirty-five species of rubiaceous plants have been examined for their iridoids by gas chromatography and/or gas chromatography-mass spectrometry and in some cases by isolation of the glycosides. The results, combined with data from other studies, suggest that these plants can be classified into three groups: (i) subfamily Ixoroideae, members of which contain gardenoside, geniposide and ixoroside; (ii) subfamily Rubioideae, all of which contain asperuloside and/or deacetylasperulosidic acid; (iii) subfamilies Cinchonoideae and Antirheoideae which contain loganin, secoiridoids, and/or indole alkaloids biosynthesized via the latter two glucosides. From this chemotaxonomic point of view, some doubt is thrown on the taxonomic position of Wendlandia formosana and plants of Mussaenda, two taxa currently placed in the Cinchonoideae but chemically allied to Ixoroideae.

Contributions to the morphology, anatomy, and karyology ofRhabdodendron, and a reconsideration of the systematic position of theRhabdodendronaceae

Rhabdodendron macrophyllum (Spruce ex Benth.)Huber andR. amazonicum (Spruce exBenth.)Huber differ in several anatomical and morphological characters (secretory cavities, hypoderm, peltate hairs, internodal region and petiole). A position of the monotypicRhabdodendronaceae in theCentrospermae as recently suggested is hardly supported: Peltate hairs, lysigenous secretory cavities and spicular cells in the leaves, multilacunar nodes, chromosome number (R. macrophyllum: n = 10; first count for the genus resp. family), ± simultaneous (or slightly centripetal) development of the androeceum, anacrostyly and two ovules in the unicarpellate gynoeceum, apparent disc, monotelic racemes, and data available from literature (pollen, sieve tube plastids) clearly indicate a close affinity toRutaceae, and even make the family rank ofRhabdodendron questionable.

Phylohydrax (Rubiaceae-Spermacoceae)—a new genus to accommodate the African and Madagascan“Hydrophylax” species

Hydrophylax, a genus of maritime strand or dune plants, was previously thought to comprise three species, one from India, Sri Lanka and Thailand (H. maritima), and two from Africa and Madagascar (“H.” carnosa and “H.” madagascariensis respectively). Evidence is presented that the African and Madagascan species are better placed into a separate genus (Phylohydrax). Differential characters betweenH. maritima andP. carnosa—P. madagascariensis, the relationships between the three species, and the affinities ofPhylohydrax andHydrophylax to otherSpermacoceae are discussed in detail.

Development and structure of the comose seeds ofHillia (Rubiaceae)

The hairs at the apical end of the seeds ofHillia are pluriseriate, multicellular structures. The cells making up a hair are elongated exotesta cells and, consequently, also have secondary thickenings identical (H. parasitica) or similar (H. costanensis) to those found on the exotesta cells on the main body of the seeds. Hair formation already starts in bud stage: at and around the chalazal region of an ovule, integument epidermis cells are grouped together to form ± elongated packets of 4–7 cells. The cells of each packet undergo further elongation and anticlinal division so that a hair on a mature seed may be up to c. 30 mm long. Basally, the seeds have a tail- to ± wing-like appendage, made up of only two cell layers, the exotesta of the ab- and adaxial side of the seed. This basal appendage shows the same anatomical structure as the wings of various anemochorous rubiaceous seeds. Although seed hairs of this kind are unique in theRubiaceae and — from the point of development and structure — not homologous to exotesta wings, the presence of a basal wing-like appendage suggests thatHillia, previously often placed into a tribe of its own (Hillieae), can be accommodated in theCinchoneae, a tribe in which winged, anemochorous seeds predominate. The tufts of hairs of the comose seeds ofHillia look superficially similar to those of certainAsclepiadaceae andApocynaceae (like theRubiaceae belonging to the orderGentianales). Comparisons based on literature data, however, reveal that there are striking differences in the position, development and structure of the hairs (produced at the micropylar end, initiated after fertilization, hairs unicellular, etc.).

Leaf flavonoids ofGalium sect.Aparinoides (Rubiaceae)

Abstract13 taxa belonging to 4 “species groups” ofGalium L. sect.Aparinoides (Jord.)Gren. produce 15 leaf flavonoids: Apigenin-7-diglucoside, Luteolin-7-monoglucoside and 7-diglucoside, Diosmetin, Diosmetin-7-monoglucoside and 7-diglucoside; Kaempferol-3-rutinoside, Kaempferol-3,7-diglucoside, Quercetin, two Quercetin-3-monoglycosides, Rutin, Quercetin-3-rutinoside-7-glucoside, Quercetin-7-glycoside and an unidentified aglycone. TheG. trifidum, G. obtusum andG. palustre groups (with the exception of theG. tinctorium subspecies andG. elongatum) have similar flavone-flavonole patterns, while theG. antarcticum group produces a specific pattern. Leaf flavonoids of theG. trifidum andG. antarcticum group are inhomogenous, becauseG. tinctorium subsp.tinctorium andG. antarcticum lack flavones. For all taxa (with the exception of those of theG. antarcticum group) intraspecific variation is demonstrated, and 4 populations ofG. trifidum subsp.trifidum, G. tinctorium subsp.tinctorium,G. obtusum subsp.obtusum andG. labradoricum even exhibit intrapopulation variation. The implications of flavonoid data on the systematics and the astonishing intrapopulation and intraspecific variation are discussed.

Intra-ovarian trichomes in Jackiopsis ornata (Wallich) Ridsdale (Rubiaceae-Jackieae)

The ovary and young fruit of Jackiopsis ornata has internal, unbranched, septate hairs which are more or less evenly dispersed over the entire interior surface of the locules and present in quite large numbers. This is the first record of intra-ovarian trichomes in the Rubiaceae. The trichomes do not seem to have an obvious function in that they do not appear to serve as a specialized pollen transmitting tissue or play a role in directing pollen tube growth.

Über die Kalkausscheidungen beiMonophyllaea horsfieldii (Gesneriaceae)

The lower surface of the leaf (macrocotyledon) ofM. horsfieldii is heavily calcified. SEM investigations reveal that the cristalline depositions of CaCO3 (mainly needles, but also clump-like structures) are excreted by the head cells of two-cellular trichomhydathodes. First, a cap-like structure is formed. As the excretion continues, the “cap” takes on the shape of a “hat with wide brim”. Thus, the dense layer of CaCO3 depositions is composed of hat-like structures whose brims at least partially touch. There is no evidence for the excretion of CaCO3 by cells other than trichomhydathodes.