Pieter Caris

A Floral Ontogenetic Approach to Questions of Homology within the Cyperoideae (Cyperaceae)

Within the Cyperoideae, which comprise all Cyperaceae except the Mapanioideae, several questions of homology are discussed and reinterpreted based on results of our SEM and LM floral ontogenetic studies. In all species studied, spikelets are interpreted as being indeterminate, with spirally to distichously arranged glumes, each subtending (or not) a flower. Floral development starts with the formation of two lateral stamen primordia, simultaneously with, or followed by the formation of a third, abaxial stamen primordium. Perianth parts, if present, originate only after the formation of the androecium, simultaneously with the appearance of an annular ovary primordium, surrounding a central ovule primordium. Perianth parts vary in number and morphology, and, where present, perianth development follows a general pattern. Three (or two) stigma primordia are formed on the top of the rising ovary wall. In dimerous gynoecia, stigma primordia originate either dorsiventrally, resulting in a laterally flattened ovary/nutlet, or laterally, resulting in a dorsiventrally flattened ovary/nutlet. We conclude that in all species studied the spikelet and floral development occurs according to a general, scirpoid, ontogenetic pattern, which we illustrate using new spikelet and floral ontogenetic results in Eleocharis palustris and other species. Spikelet and floral ontogeny in species with apparently deviating morphologies, can be traced back to the general ontogenetic pattern.ResumenVarias preguntas sobre homología para las Cyperoideae, que incluyen todas las Cyperaceae excepto las Mapanioideae, se discuten e interpretan con base en estudios de ontogenia floral realizados con SEM y LM. En todas las especies estudiadas, las espiguillas son indeterminadas con glumas arregladas en espiral o dicotomicamente, cada una sosteniendo (o no) una flor. El desarrollo floral comienza con la formación de dos primordios estaminales laterales, simultáneamente con o seguido por la formación del tercer primordio estaminal abaxial. Si se desarrollan las partes del perianto, se originan solo después de la formación del androceo, simultáneamente con el desarrollo del primordio anular del ovario que envuelve al primordio central del óvulo. Cuando están presentes las partes del perianto, varían en número y morfología y el desarrollo sigue un patrón general. Se forman tres (o dos) primordios del estigma en el ápice de la pared del ovario en desarrollo. En gineceos dímeros, los primordios de los estigmas se originan dorsiventralmente resultando en una nuececilla/ovario comprimido lateralmente, o se originan lateralmente, resultando en una nuececilla/ovario comprimido dorsiventralmente. Concluimos que, tanto el desarrollo floral, como el de las espiguillas en todas las especies estudiadas, siguen un patrón ontogenético general scirpoide que se ilustra con los resultados obtenidos para Eleocharis palustris y otros especies. La ontogenia floral y de las espiguillas en especies con morfologías aparentemente atípicas, puede estar reducida al patrón ontogenetico general.

A floral ontogenetic study on the sister group relationship between the genus Samolus (Primulaceae) and the Theophrastaceae

The former Primulales used to be subdivided into the woody Theophrastaceae and Myrsinaceae, from the tropics and subtropics, and the herbaceous Primulaceae, which are mainly found in the temperate regions of the northern hemisphere. Recent analyses based on morphological as well as molecular data revealed a close relationship between the genus Samolus L. of Primulaceae and the monophyletic family Theophrastaceae. We studied the floral development of six species from four different genera of Theophrastaceae and compared it to floral ontogenetical data of Samolus valerandi L. to find support for a close relationship. Samolus and the members of Theophrastaceae share the presence of staminodes and a similar development of the placenta and the ovules. Apart from the different habit and distribution, however, we also observed some major differences between both lineages, such as the absence of common primordia in Theophrastaceae, the development of a gynoecial cap in Samolus, and the difference in development, shape, and structure of the staminodes. Therefore, we propose to keep Samolus separated from the genera of the Theophrastaceae, and we suggest that it be raised to family level.

The Uncertain Systematic Position of Symplocos (Symplocaceae): Evidence from a Floral Ontogenetic Study

Recent molecular analyses show considerable variation in family interrelationships of Ericales sensu lato. Here, we will review the proposed phylogenetic relationships of the monogeneric Symplocaceae on the basis of floral morphological evidence. Scanning electron microscopy observations of the floral development of Symplocos paniculata Miq. show that some characteristics that were used to determine the position of the family seem to have been misinterpreted by different authors: placentation and number and position of the ovules in the species studied differ from general descriptions of the genus; the reported presence of bracts and bracteoles in all members of the family needs to be confirmed. From a floral ontogenetic point of view, it seems reasonable to consider Symplocaceae to be a member of Ericales sensu lato, where most of the apparently related taxa are classified.

Transference of function shapes organ identity in the dove tree inflorescence

• An important evolutionary mechanism shaping the biodiversity of flowering plants is the transfer of function from one plant organ to another. To investigate whether and how transference of function is associated with the remodeling of the floral organ identity program we studied Davidia involucrata, a species with conspicuous, petaloid bracts subtending a contracted inflorescence with reduced flowers. • A detailed ontogeny enabled the interpretation of expression patterns of B-, C- and E-class homeotic MADS-box genes using qRT-PCR and in situ hybridization techniques. We investigated protein-protein interactions using yeast two-hybrid assays. • Although loss of organs does not appear to have affected organ identity in the retained organs of the reduced flowers of D. involucrata, the bracts express the B-class TM6 (Tomato MADS box gene 6) and GLOBOSA homologs, but not DEFICIENS, and the C-class AGAMOUS homolog, representing a subset of genes also involved in stamen identity. • Our results may illustrate how petal identity can be partially transferred outside the flower by expressing a subset of stamen identity genes. This adds to the molecular mechanisms explaining the diversity of plant reproductive morphology.

Comparative Wood Anatomy of the Primuloid Clade (Ericales s.l)

Abstract The wood structure of 78 species from 27 genera representing the woody primuloids (Maesaceae, Myrsinaceae, and Theophrastaceae) was investigated using light microscopy (LM) and scanning electron microscopy (SEM). Results indicated that the ray structure, the nature of mineral inclusions, and the occurrence of breakdown areas in rays can be used to separate the three primuloid families from each other. Within Ericales, the presence of exclusively multiseriate rays is synapomorphic for Myrsinaceae and Theophrastaceae, and the occurrence of breakdown areas in rays is synapomorphic for Myrsinaceae. Within Myrsinaceae, the wood structure of the mangrove genus Aegiceras differs because it has short vessel elements that are storied, non-septate fibers, a combination of low uni- and multiseriate rays, and multiseriate rays with exclusively procumbent body ray cells. The aberrant wood anatomy of Coris and Lysimachia can be explained by their secondary woodiness. Within Theophrastaceae, Clavija and Theophrasta can be distinguished from Bonellia, Jacquinia, and Deherainia. The recent division of Jacquinia s.l. into Jacquinia s.s. and Bonellia is supported by a difference in mineral inclusions.