Recent insight in the phylogeny of the Rubiaceae, mainly based on macromolecular data, agrees better with wood anatomical diversity patterns than previous subdivisions of the family. The two main types of secondary xylem that occur in Rubiaceae show general consistency in their distribution within clades. Wood anatomical characters, especially the fibre type and axial parenchyma distribution, have indeed good taxonomic value in the family. Nevertheless, the application of wood anatomical data in Rubiaceae is more useful in confirming or negating already proposed relationships rather than postulating new affinities for problematic taxa. The wood characterised by fibre-tracheids (type I) is most common, while type II with septate libriform fibres is restricted to some tribes in all three subfamilies. Mineral inclusions in wood also provide valuable information with respect to systematic relationships.
The presence of exceptionally large styloid crystals in the secondary xylem of Cosmocalyx spectabilis Standl. (Rubiaceae) is reported. These crystals are rather unusual also in terms of habit, structure, and distribution.
Six plantation grown Kelempayan trees [Neolamarckia cadamba (Roxb.) Bosser, syn. Anthocephalus chinensis (Lamk.) A. Rich. ex Walp., Rubiaceae] were sampled along their radii and at five different height levels to evaluate variations of wood anatomical properties. Analysis of variance indicates that between tree differences in all anatomical properties measured were significant. Vessel proportion increases while ray proportion decreases with height, while both fibre diameter and fibre lumen diameter decrease with height. No significant trend was found for fibre length vertically. Cell wall substance and vessel and ray proportion increase from pith to bark, while fibre proportion decreases. Fibre length and fibre wall thickness increase from pith to bark, while fibre diameter and fibre lumen diameter first increase and then decrease. Within-tree variations are more consistent radially than vertically.
The chrome azurol-S test, which is a chemical spot-test for Al accumulation in wood, was applied to 443 wood samples of members of the Rubiaceae. A positive reaction was found in 103 specimens. Comparison of the results with earlier analyses of leaves of Rubiaceae shows that Al accumulation occurs more frequently in leaves than in wood. The strongest Al accumulators occur in the neotropical genera Psychotria subg. Heteropsychotria, Coussarea, Faramea, and Rudgea. The distribution of Al accumulators is discussed in view of recent tribal and subfamilial classification of the Rubiaceae. The major conclusion is that Al accumulation is almost limited to the subfamily Rubioideae. Within the Rubioideae, however, not all tribes show the character, especially the predominantly herbaceous Anthospermeae, Paederieae, Rubieae, and Spermacoceae. Al accumulation in the Urophylleae, Pauridiantheae, Craterispermeae, and Knoxieae supports earlier associations of these tribes with the Rubioideae.
We studied wood and bark anatomy of six (Deppea, Hamelia, Hoffmannia, Omiltemia, Pinarophyllon, and Plocaniophyllon) of the seven genera of the tribe Hamelieae sensu Robbrecht, and Syringantha with as main purposes to determine if there are characters that support the boundaries of the Hamelieae, to evaluate the status of Syringantha as a member of the Hamelieae, and to evaluate the taxonomic position of Hamelieae within the subfamilies Rubioideae or Cinchonoideae. In addition, we studied for comparative purposes representative species of Psychotria (Psychotrieae, Rubioideae), Exostema, and Hintonia (Portlandia group, Cinchonoideae), Randia (Gardenieae, Ixoroideae), and Bouvardia (incertae sedis). Bark of most genera studied had a single periderm, while a rhytidome was observed in Exostema and few species of Psychotria. The mineral inclusions allowed recognizing related genera, for example, raphides in Hamelieae and Psychotria, prisms in Exostema, and druses in Randia. Members of Hamelieae showed wood type II, distinctive by the occurrence of libriform septate fibres, vessels in radial multiples of 2–6 vessels (80–90%, vessel grouping index 1.79–2.74), and diffuse apotracheal parenchyma. Syringantha shares with members of Hamelieae the presence of an endodermis, raphides in the bark, and wood type II. The combination of other wood characters mainly lend quantitative support to the taxonomic delimitation of some genera within Hamelieae. Raphides and wood type II supported a close relationship between Hamelieae and Hillieae within Cinchonoideae; characters that distinguish them from the other members of Cinchonoideae. Our results suggest independent origins of wood type II within the Rubiaceae. In addition, vessel density and diameter are discussed as possible adaptations to the different forest types where members of Hamelieae occur.
corymbosa L. (Rubiacée tropicale). Physiol. Veg. 1980 18 275 287
Corbineau F. Côme D. Some particularities of the germination of Oldenlandia corymbosa L. seeds (tropical Rubiaceae) Isr. J. Bot. 1980/81 29 157 167
Corbineau F. Côme D. Principales caractéristiques de la photoblastie des graines d
Nematology , 2011, Vol. 13(1), 29-44 Litylenchus coprosma gen. n., sp. n. (Tylenchida: Anguinata), from leaves of Coprosma repens (Rubiaceae) in New Zealand Zeng Qi Z HAO 1 , ∗ , Kerrie D AVI ES 2 , Brett A LEXANDER 3 and Ian T. R ILEY 4 1 Landcare Research, Private Bag 92170, Auckland Mail
This paper describes the morphology and size of perforated ray cells in Bathysa meridionalis Smith & Downs and compares its features with the adjacent ray cells and vessel elements. The perforated ray cells are much bigger and more voluminous than normal ray cells. Their shapes vary from ellipsoid to polygonal. The perforation plates may be solitary to tree per wall, round to reniform. The dimensions of perforated ray cells suggest that they are at least as effective for water flow as axial vessel elements.
Oldenlandia corymbosa seeds can only germinate in the light and at very high temperatures (optimum at 35–40°C). Two types of seeds exist: those that germinate rapidly in continuous white light at 35–40°C are regarded as “non-dormant”; the others which are unable to germinate under the same conditions without having been treated for some days at a fairly low temperature (<25°C) in a wet medium are “dormant”. The requirement for high germination temperatures is characteristic of the embryo, while the absolute need for light and the inability of dormant seeds to germinate are characteristic of the endosperm and seed coat. The dormancy of these seeds is, in fact, an inhibition caused by the structures covering the Oldenlandia embryo. Seeds are hypersensitive to oxygen. At the optimal germination temperature some of them germinate rapidly within a wide range of oxygen partial pressures. They germinate particularly well in the air. These are the so-called “non-dormant” seeds. Others germinate well at this temperature only in atmospheres containing 5–10% oxygen. These seeds, which germinate with difficulty in the air, are the “dormant” ones. If dormant seeds do not germinate in the air, it is thus because of an excess of oxygen. Again, this phenomenon is caused by the endosperm and the seed coat and not by the embryo. These peculiarities in the germination of Oldenlandia corymbosa seeds are probably bound up with the tropical climate.