Floral morphology and development reveal extreme diversification in some species of Croton (Euphorbiaceae).

Floral diversity of Croton, the second largest genus in Euphorbiaceae, is currently under-explored. Several clades demonstrate an unusual floral morphology, e.g.

The interaction between heterochrony and mechanical forces as main driver of floral evolution.

Heterochrony acts as a fundamental process affecting the early development of organisms in creating a subtle shift in the timing of initiation or the duration of a developmental process. In flowers this process is linked with mechanical forces that cause changes in the interaction of neighbouring floral organs by altering the timing and rate of initiation of organs. Heterochrony leads to a delay or acceleration of the development of neighbouring primordia, inducing a change in the morphospace of the flowers.

Mechanical Forces in Floral Development.

Mechanical forces acting within the plant body that can mold flower shape throughout development received little attention. The palette of action of these forces ranges from mechanical pressures on organ primordia at the microscopic level up to the twisting of a peduncle that promotes resupination of a flower at the macroscopic level. Here, we argue that without these forces acting during the ontogenetic process, the actual flower phenotype would not be achieved as it is.

Gynoecium structure in Sapindales and a case study of Trichilia pallens (Meliaceae).

Sapindales is a monophyletic order within the malvid clade of rosids. It represents an interesting group to address questions on floral structure and evolution due to a wide variation in reproductive traits. This review covers a detailed overview of gynoecium features, as well as a new structural study based on Trichilia pallens (Meliaceae), to provide characters to support systematic relationships and to recognize patterns of variations in gynoecium features in Sapindales.

What is the nature of petals in Caryophyllaceae? Developmental evidence clarifies their evolutionary origin.

Background And Aims: Floral development is a powerful tool to infer homologies of floral organs and to understand floral evolution. Caryophyllaceae is a major family of core Caryophyllales that possesses petal-like structures (petaloids) with a great diversity in shape. The main purpose of this study is to determine the nature of the second whorl of floral organs in Caryophyllaceae.

Unbuttoning the Ancestral Flower of Angiosperms.

A recent study using an extensive data set plus sophisticated analytical tools reconstructed a model of the ancestral angiosperm flower. Although attractive, it presents problems of homology assessment. We discuss its inconsistencies and endorse the use of a comparative model that integrates biological parameters as essential to elucidate floral evolution.

Correction to: Floral development of petaloid Alismatales as an insight into the origin of the trimerous Bauplan in monocot flowers.

The caption of Figure 5 was published incorrectly in the original publication of the article.

Understanding the role of floral development in the evolution of angiosperm flowers: clarifications from a historical and physico-dynamic perspective.

Flower morphology results from the interaction of an established genetic program, the influence of external forces induced by pollination systems, and physical forces acting before, during and after initiation. Floral ontogeny, as the process of development from a meristem to a fully developed flower, can be approached either from a historical perspective, as a "recapitulation of the phylogeny" mainly explained as a process of genetic mutations through time, or from a physico-dynamic perspective, where time, spatial pressures, and growth processes are determining factors in creating the floral morphospace. The first (historical) perspective clarifies how flower morphology is the result of development over time, where evolutionary changes are only possible using building blocks that are available at a certain stage in the developmental history.

Floral morphology and morphogenesis in Camptotheca (Nyssaceae), and its systematic significance.

Background And Aims: Camptotheca is endemic to China and there are limited data about the breeding system and morphogenesis of the flowers. Camptotheca is thought to be related to Nyssa and Davidia in Nyssaceae, which has sometimes been included in Cornaceae. However, molecular phylogenetic studies confirmed the inclusion of Camptotheca in Nyssaceae and its exclusion from Cornaceae.

Floral meristem size and organ number correlation in Eucryphia (Cunoniaceae).

We present a comparative flower ontogenetic study in five species of the genus Eucryphia with the aim of testing whether differences in the organ number observed can be explained by changes in the meristematic size of floral meristem and floral organs. Species native to Oceania, viz. E.

Floral development of petaloid Alismatales as an insight into the origin of the trimerous Bauplan in monocot flowers.

Monocots are remarkably homogeneous in sharing a common trimerous pentacyclic floral Bauplan. A major factor affecting monocot evolution is the unique origin of the clade from basal angiosperms. The origin of the floral Bauplan of monocots remains controversial, as no immediate sister groups with similar structure can be identified among basal angiosperms, and there are several possibilities for an ancestral floral structure, including more complex flowers with higher stamen and carpel numbers, or strongly reduced flowers.

Obdiplostemony: the occurrence of a transitional stage linking robust flower configurations.

Background And Aims: Obdiplostemony has long been a controversial condition as it diverges from diplostemony found among most core eudicot orders by the more external insertion of the alternisepalous stamens. In this paper we review the definition and occurrence of obdiplostemony, and analyse how the condition has impacted on floral diversification and species evolution.

Key Results: Obdiplostemony represents an amalgamation of at least five different floral developmental pathways, all of them leading to the external positioning of the alternisepalous stamen whorl within a two-whorled androecium.

Floral anatomy and vegetative development in Ceratophyllum demersum: a morphological picture of an "unsolved" plant.

Premise Of The Study: The phylogenetic position of Ceratophyllum is still controversial in recent molecular analyses of angiosperms, with various suggestions of a sister group relation to all other angiosperms, eudicots, monocots, eudicots + monocots, and magnoliids. Therefore, the morphological characters of Ceratophyllum are important for resolving the phylogeny of angiosperms. In this study, we observed the detailed developmental anatomy of all lateral organs and their configurations to elucidate the floral development and phyllotactic pattern of Ceratophyllum demersum.

Floral development of Sabia (Sabiaceae): evidence for the derivation of pentamery from a trimerous ancestry.

Unlabelled: •

Premise Of The Study: Flowers of Sabiaceae diverge from basal eudicots in combining pentamery with superposed whorls of sepals, petals, and stamens and are therefore crucial in understanding origins of core eudicot flowers. Different hypotheses are tested using floral developmental evidence, whether the pentamerous flower is derived from a spiral, trimerous, or dimerous progenitor.•

Methods: The floral development of two species of Sabia was investigated with the scanning electron microscope to understand their unusual floral morphology and the origin of pentamery.

Androecial evolution in Caryophyllales in light of a paraphyletic Molluginaceae.

Premise Of The Study: Caryophyllales are highly diverse in the structure of the perianth and androecium and show a mode of floral development unique in eudicots, reflecting the continuous interplay of gynoecium and perianth and their influence on position, number, and identity of the androecial whorls. The floral development of five species from four genera of a paraphyletic Molluginaceae (Limeum, Hypertelis, Glinus, Corbichonia), representing three distinct evolutionary lineages, was investigated to interpret the evolution of the androecium across Caryophyllales. •

Methods: Floral buds were dissected, critical-point dried and imaged with SEM.

Asymmetric morphogenetic cues along the transverse plane: shift from disymmetry to zygomorphy in the flower of Fumarioideae.

Premise Of The Study: Zygomorphy has evolved multiple times in angiosperms. Near-actinomorphy is the ancestral state in the early diverging eudicot family Papaveraceae. Zygomorphy evolved once in the subfamily Fumarioideae from a disymmetric state.

Carpeloidy in flower evolution and diversification: a comparative study in Carica papaya and Arabidopsis thaliana.

Background And Aims: Bisexual flowers of Carica papaya range from highly regular flowers to morphs with various fusions of stamens to the ovary. Arabidopsis thaliana sup1 mutants have carpels replaced by chimeric carpel-stamen structures. Comparative analysis of stamen to carpel conversions in the two different plant systems was used to understand the stage and origin of carpeloidy when derived from stamen tissues, and consequently to understand how carpeloidy contributes to innovations in flower evolution.

Anatomical features associated with water transport in imperforate tracheary elements of vessel-bearing angiosperms.

Background And Aims: Imperforate tracheary elements (ITEs) in wood of vessel-bearing angiosperms may or may not transport water. Despite the significance of hydraulic transport for defining ITE types, the combination of cell structure with water transport visualization in planta has received little attention. This study provides a quantitative analysis of structural features associated with the conductive vs.

Floral ontogeny of Annonaceae: evidence for high variability in floral form.

Background And Aims: Annonaceae are one of the largest families of Magnoliales. This study investigates the comparative floral development of 15 species to understand the basis for evolutionary changes in the perianth, androecium and carpels and to provide additional characters for phylogenetic investigation.

Methods: Floral ontogeny of 15 species from 12 genera is examined and described using scanning electron microscopy.

Floral development and anatomy of Salvadoraceae.

Unlabelled: BACKGROUND AND AIMS; This study is an investigation into the floral development and anatomy of two genera of the small family Salvadoraceae, which belongs to the Brassicales in a clade with Batis and Koeberlinia. Salvadoraceae remains little known, despite its wide distribution in arid areas of the globe. Floral morphological data are scarce, and information on floral anatomy is limited to a single study, although morphological and anatomical characters are now used increasingly as a counterpart of molecular data.

Establishment of zygomorphy on an ontogenic spiral and evolution of perianth in the tribe Delphinieae (Ranunculaceae).

Background And Aims: Ranunculaceae presents both ancestral and derived floral traits for eudicots, and as such is of potential interest to understand key steps involved in the evolution of zygomorphy in eudicots. Zygomorphy evolved once in Ranunculaceae, in the speciose and derived tribe Delphinieae. This tribe consists of two genera (Aconitum and Delphinium s.

Floral developmental evidence for the systematic position of Batis (Bataceae).

Molecular phylogenies have associated Bataceae with Salvadoraceae and Koeberliniaceae in an expanded Brassicales. Despite a long taxonomic history, the knowledge of the flower of Batis is still fragmentary. The floral development of pistillate and staminate inflorescences of Batis maritima was investigated to understand homologies of floral structures and to discuss the phylogenetic position of Bataceae within the Brassicales.