Floral Form Research Articles

Pollen resistance to water in 80 angiosperm species: flower structures protect rain‐susceptible pollen

Flowers exhibit adaptive responses to biotic and abiotic factors. It remains unclear whether pollen susceptibility to rain damage plays a role in the evolution of floral form. We investigated flower performance in rain and compared pollen longevity in dry conditions, pure water and solutions with different sucrose concentrations in 80 flowering species from 46 families with diverse floral shapes and pollination modes. A pollen viability test showed that pollen longevity in all studied species was greatly reduced by wetting. We found that pollen of species with complete protection by flower structures was susceptible to water damage and a high proportion of resistant pollen occurred in unprotected species. Flowers whose structures expose pollen to rain may also reduce rain damage through temporal patterns of pollen presentation. This prediction was supported by our direct measurement of pollen presentation duration on rainy days. Our observations showed that variation in pollen performance in water was associated with differences in floral forms. Water-resistant pollen and extended pollen presentation duration were favored by selection via rain contact in species in which pollen was not protected from rain. These findings support the functional hypothesis that flower structures protect susceptible pollen from rain, demonstrating that rain acts as a force shaping floral form.

Darwinism renewed: contemporary studies of plant adaptation

Darwinism renewed: contemporary studies of plant adaptation

Regeneration and plantlet development from somatic tissues of Aristolochia fimbriata

Aristolochia fimbriata is a small herbaceous perennial in the basal angiosperm family Aristolochiaceae. The family contains diverse floral forms ranging from radial to monosymmetric flowers with a wide variety of insect pollinators. Additionally, Aristolochia species contain secondary metabolites that are important natural toxins and traditional medicines, and are critical to the reproduction of swallowtail butterflies. These characteristics, in combination with the small genome size and short life cycle of A. fimbriata, have prompted further development of this species as a model system to study the evolution of basal angiosperms. As a prerequisite for developing a genetic transformation procedure for Aristolochia, we developed protocols for in vitro plant multiplication, shoot organogenesis, rooting, and acclimation of tissue culture-derived plants. Two varieties of Aristolochia were multiplied in vitro and rooted with 100% efficiency. Shoot regeneration was achieved within 1 month of culture initiation from whole leaf, internodal stem, and petiole explants. The highest regeneration success (97%) was recorded for stem explants. Regenerated and rooted shoots were acclimated to greenhouse conditions and developed flowers within 4 weeks of transplanting.

The evolution of floral variation without pollinator shifts inGorteria diffusa(Asteraceae)

One of the most widely accepted explanations for floral diversification in angiosperms is the pollinator-shift model developed by Verne Grant and Ledyard Stebbins. According to this model, the most profound changes in floral traits (such as morphology, color, patterning and scent) occur when plants undergo adaptive shifts between pollinator classes. We tested this model through investigations of geographical variation in floral form and pollinator assemblages in the South African annual daisy Gorteria diffusa. This species has elaborate insect-like ornaments on the capitulum, which attract bee flies belonging to the genus Megapalpus. We found unprecedented levels of geographically structured intraspecific variation and identified 14 discrete forms that vary in the morphology and ornamentation of the capitulum. This variation is not due to phenotypic plasticity because differences among forms were maintained in plants grown from seed in a common garden experiment. Contrary to predictions from the pollinator-shift model, all populations, regardless of floral phenotype, were pollinated primarily by a single species of Megapalpus bee fly. Much of the extensive variation in floral form in G. diffusa therefore appears to have arisen without evolutionary shifts between pollinator types.

Understanding flowers and flowering: an integrated approach

Understanding flowers and flowering: an integrated approach

Effects of condensation techniques and canal sizes on the microleakage of orthograde MTA apical plug in simulated canals

The purpose of this study was to compare the dye leakage of MTA (mineral trioxide aggregate) apical plug produced by two orthograde placement techniques (hand condensation technique and ultrasonically assisted hand condensation technique). To simulate straight canal, 60 transparent acrylic blocks with straight canal were fabricated. These transparent acrylic blocks were divided into 2 groups (Group C; hand condensation technique (HC) and Group U; ultrasonically assisted hand condensation technique (UAHC)) of 30 blocks with each MTA application method. Each group was divided into 2 subgroups (n=15) with different canal size of #70 (subgroup C70 and subgroup U70) and #120 (subgroup C120 and subgroup U120). After apical plug was created, a wet paper point was placed over the MTA plug and specimen was kept in a humid condition at room temperature to allow MTA to set. After 24 hours, remaining canal space was backfilled using Obtura II. All specimens were transferred to floral form socked by 0.2% rhodamine B solution and stored in 100% humidity at room temperature. After 48 hours, resin block specimens were washed and scanned using a scanner. The maximum length of micro leakage was measured from the scanned images of four surfaces of each resin block using Photoshop 6.0. Statistical analysis was performed with Mann-Whitney U test. Group U of UAHC had significantly lower leakage than Group C of HC in #70-size canal (subgroup U70) (p

Phylogeny and Floral Diversity in the GenusGarcinia(Clusiaceae) and Relatives

The pantropical genus Garcinia comprises more than 250 species of dioecious trees and shrubs that are a common component of lowland tropical forests. The genus exhibits as extreme a diversity of floral form as is found anywhere in angiosperms, and there are many unresolved taxonomic issues surrounding it. To evaluate morphology‐based classification schemes involving Garcinia and its relatives and to examine floral diversity in the genus within a phylogenetic context, higher‐level relationships among a broad sample of Garcinia and close relatives were inferred by conducting Bayesian, parsimony, and likelihood analyses of 70 species with sequence data from two nuclear genes, granule‐bound starch synthase (GBSSI) and the internal transcribed spacer (ITS). These results support a broad circumscription of Garcinia and the monophyly of tribe Garcinieae. Within Garcinia, several clades are supported that share particular combinations of floral characters and generally correspond to sections recognized in the mos...

갈색여치(Paratlanticus ussuriensis)의 산란 특성

Paratlanticus ussuriensis oviposited from early July to mid-September under laboratory condition. A female laid on average 145 eggs during the period of reproduction and over 54% of the eggs were laid within 2 weeks after the first laying. The average depth of egg-laying in soil was 19.4 mm under surface. The average major axis of an egg was 5.7 mm and the minor axis was 2.0 mm. Just before hatching, the egg swelled about twice the weight of a newly laid. In tests of ovipositional preference in different types of media, more eggs were laid in soil than in vermiculite or in Oasis ® floral form. Females also prefer shaded places in the field for reproduction, away from sunshine. In terms of the strategy for egg survival, adult moves to the hill-side adjacent to orchard farm to find a proper place for their egg laying and its survival in winter.

The long and the short of gene flow and reproductive isolation: Inter-Simple Sequence Repeat (ISSR) markers support the recognition of two floral forms in Pelargonium reniforme (Geraniaceae)

The current taxonomy of Pelargonium reniforme recognises two subspecies on the basis of habit and vegetative characters, but excludes floral characters. However, populations of P. reniforme in the wild tend to belong to easily discernable floral groups based on floral colour and hypanthium length. The aim of this study was to determine the genetic diversity within and between populations of both subspecies using the Inter-Simple Sequence Repeat (ISSR) method of DNA fingerprinting. Ninety individuals from eight populations were sampled. Both phenetic and Neighbor-Net analyses reveal that populations are genetically discernable, but that there is no genetic evidence to support the recognition of the two currently defined subspecies of P. reniforme. Instead, the analyses resolved all individuals that possess long hypanthia into a single group, and the role of different pollinators in driving reproductive isolation of this long-tubed form is suggested.

DOT/UFO Emerges as a Key Factor in Inflorescence Patterning

Flowering plants exhibit an astonishing variety of floral forms, which arise from two basic patterns of floral meristem initiation: determinate and indeterminate. Many indeterminate inflorescences show some variation of a racemose pattern, which maintains an apical meristem and produces flowers

Genetic control of floral zygomorphy in pea (Pisum sativum L.).

Floral zygomorphy (flowers with bilateral symmetry) has multiple origins and typically manifests two kinds of asymmetries, dorsoventral (DV) and organ internal (IN) asymmetries in floral and organ planes, respectively, revealing the underlying key regulators in plant genomes that generate and superimpose various mechanisms to build up complexity and different floral forms during plant development. In this study, we investigate the loci affecting these asymmetries during the development of floral zygomorphy in pea (Pisum sativum L.). Two genes, LOBED STANDARD 1 (LST1) and KEELED WINGS (K), were cloned that encode TCP transcription factors and have divergent functions to constitute the DV asymmetry. A previously undescribed regulator, SYMMETRIC PETALS 1 (SYP1), has been isolated as controlling IN asymmetry. Genetic analysis demonstrates that DV and IN asymmetries could be controlled independently by the two kinds of regulators in pea, and their interactions help to specify the type of zygomorphy. Based on the genetic analysis in pea, we suggest that variation in both the functions and interactions of these regulators could give rise to the wide spectrum of floral symmetries among legume species and other flowering plants.

The Poetry of Reproduction

Flowers are not only ‘‘example of the eternal seductiveness of life’’ but flowers are also fascinating in their own rights, and ‘‘Understanding Flowers and Flowering’’ is an intellectually seductive journey into the fascinating world of plant reproduction (Fig. 1). Did you ever wonder how flowers might have evolved? What the German poet Johann Wolfgang von Goethe has to do with flowers? Which signalling pathways induce flowering? What happens at the shoot apical meristem after floral induction? How do flowers develop? What are the D and E in the ABC model? Which strategies exist to prevent self-pollination? How can flower development be modified to change floral shape and structure? What makes flowers so colourful? What kind of pollen vectors can mediate cross-pollination? Are flowers under selective pressure to increase attractiveness for pollinators? Do pollinators differentiate between different floral forms, colours or scents? Many of these questions have been discussed in the context of ‘‘pollination syndromes’’, i.e. the matching adaptation of certain flowers and specific pollinators caused by coevolution. But what is the evidence that pollination syndromes really exist? To find answers to these and many other questions you should read this book! ‘‘Flowers and Flowering’’ delivers a detailed discussion of flowering time control including a chapter about historical development of the flowering concept. Surprisingly, the famous Maryland Mammoth tobacco is never mentioned, and William Garner’s and Harry Allard’s desperate 12-yearlong search for the physiological signal that allows flowering is not mentioned. It was not pure scientific curiosity but the great economic impact a non-flowering tobacco could have that drove the first systematic and detailed analysis of flowering control eventually establishing the concept of photoperiodic control of flowering (Garner and Allard 1920). Anecdotal information could also have enriched the chapter about the famous foliar theory originally proposed by Goethe (Goethe 1790). As pointed out in the book, Goethe thought of all plant organs analogous to a single type organ (the Blatt = leaf), but he did not imply any evolutionary or developmental concept. Thus, while we think that petals are organs derived from leaves, he thought of petals and leaves as different manifestations of a single idea – the Blatt. It has been argued that this view of Goethe is essentially idealistic (Platonian) (May 1913), and the deleterious consequences of idealistic philosophy for the idea of evolution to become generally accepted has been discussed in detail (Mayr 1982). Philosophical idealisms led Goethe to propose the foliar theory, and philosophical idealisms prevented Goethe from seeing the developmental and evolutionary interpretation of the foliar theory. While focussing on the foliar theory, another revolutionary aspect is often overlooked: Goethe used mutants to derive his conclusions! While his contemporary naturalists were convinced that in order to understand the normal, one has to study the normal, Goethe proposed to study ‘‘freaks’’ to understand the normal. He used floral mutants, selected by gardeners for their ornamental value such as filled roses, to derive conclusions about normal development. Much later developmental genetics led to the discovery of homeotic transformations and the basic mechanisms of flower development, and these results are described in several detailed chapters in ‘‘Flowers and Flowering’’. L. Hennig (&) Institute of Plant Sciences and Zurich-Basel Plant Science Center, ETH Zurich, 8092 Zurich, Switzerland e-mail: lhennig@ethz.ch

THE GENETIC ARCHITECTURE OF REPRODUCTIVE ISOLATION IN LOUISIANA IRISES: POLLINATION SYNDROMES AND POLLINATOR PREFERENCES

In animal-pollinated plants, pollinator preferences for divergent floral forms can lead to partial reproductive isolation. We describe regions of plant genomes that affect pollinator preferences for two species of Louisiana Irises, Iris brevicaulis and Iris fulva, and their artificial hybrids. Iris brevicaulis and I. fulva possess bee and bird-pollination syndromes, respectively. Hummingbirds preferred I. fulva and under-visited both I. brevicaulis and backcrosses toward this species. Lepidopterans preferred I. fulva and backcrosses toward I. fulva, but also under-visited I. brevicaulis and I. brevicaulis backcrosses. Bumblebees preferred I. brevicaulis and F1 hybrids and rarely visited I. fulva. Although all three pollen vectors preferred one or the other species, these preferences did not prevent visitation to other hybrid/parental classes. Quantitative trait locus (QTL) mapping, in reciprocal BC1 mapping populations, defined the genetic architecture of loci that affected pollinator behavior. We detected six and nine QTLs that affected pollinator visitation rates in the BCIb and BCIf mapping populations, respectively, with as many as three QTLs detected for each trait. Overall, this study reflects the possible role of quantitative genetic factors in determining (1) reproductive isolation, (2) the pattern of pollinator-mediated genetic exchange, and thus (3) hybrid zone evolution.

Quantitative measures of leaf epidermal cells as a taxonomic and phylogenetic tool for the identification of Stanhopea species (Orchidaceae)

Orchids of the genus Stanhopea are currently identified only by their floral structure characteristics. A statistical analysis of a sig- nificant number of species of this genus disclosed that measurements of adaxial and abaxial epidermal cell surface areas can be correlated with spe- cific recognized species by a leaf printing method. This allows an objective- ly either positive or nearly positive confirmation of the identity of a species in the absence of flowers and without damage to plants. When ordering the mean values obtained for these surface areas in each species in a decreas- ing order, a correlation was observed in a hierarchical way that went from primitive to more advanced floral forms. This reflects the evolutionary radi- ation of the genus. It is established that in Stanhopea, the presence of large leaf epidermal cells on species from South America represents a primitive evolutionary condition that became to smaller cells in evolutionarily more recent individuals as the genus radiated towards Mexico.

Parallel floral adaptations to pollination by fungus gnats within the genus Mitella (Saxifragaceae)

The widespread pattern of parallel flower evolution as an adaptation for particular pollinator agents, known as “pollination syndromes”, has long drawn attention from evolutionary biologists. Here, we report parallel evolution of saucer-shaped flowers and an associated unusual pollination system within the lineage Heucherina, a group of saxifragaceous genera. Field observations reveal that 18 of 28 plant species studied are pollinated almost exclusively by fungus gnats (Mycetophilidae). Among the 18 species with a fungus-gnat pollination system, 13 have characteristic saucer-shaped flowers and are pollinated mainly by several unspecialized mycetophilid genera with short mouthparts. We performed phylogenetic analyses using nucleotide sequences of external and internal transcribed spacers of nuclear ribosomal DNA and reconstructed ancestral floral morphologies with an establishment of the model of floral character evolution under a maximum-likelihood framework. Our analysis indicates that there is significant directionality in the evolutionary shifts of floral forms in the Heucherina. The inferred phylogeny further supports four origins of saucer-shaped flowers, which is shared among 14 species that are traditionally classified into the genus Mitella. In addition, our analysis indicates the extensive polyphyly of genus Mitella, as also suggested previously. The results suggest that the flower-visiting fungus gnats have caused convergent selection for the saucer-shaped flower repeatedly evolved within Heucherina.

Evolution of perianth and stamen characteristics with respect to floral symmetry in Ranunculales.

Floral symmetry presents two main states in angiosperms, namely polysymmetry and monosymmetry. Monosymmetry is thought to have evolved several times independently from polysymmetry, possibly in co-adaptation with specialized pollinators. Monosymmetry commonly refers to the perianth, even though associated androecium modifications have been reported. The evolution of perianth symmetry is examined with respect to traits of flower architecture in the Ranunculales, the sister group to all other eudicots, which present a large diversity of floral forms. Characters considered were perianth merism, calyx, corolla and androecium symmetry, number of stamens and spurs. Character evolution was optimized on a composite phylogenetic tree of Ranunculales using maximum parsimony. The ancestral state for merism could not be inferred because the basalmost Eupteleaceae lack a perianth and have a variable number of stamens. The Papaveraceae are dimerous, and the five other families share a common trimerous ancestor. Shifts from trimery to dimery (or reverse) are observed. Pentamery evolved in Ranunculaceae. Ranunculales except Eupteleaceae, present a polysymmetric ancestral state. Monosymmetry evolved once within Papaveraceae, Ranunculaceae and Menispermaceae (female flowers only). Oligandry is the ancestral state for all Ranunculales, and polyandry evolved several times independently, in Papaveraceae, Menispermaceae, Berberidaceae and Ranunculaceae, with two reversions to oligandry in the latter. The ancestral state for androecium symmetry is ambiguous for the Ranunculales, while polysymmetry evolved immediately after the divergence of Eupteleaceae. A disymmetric androecium evolved in Papaveraceae. The ancestral state for spurs is none. Multiple spurs evolved in Papaveraceae, Berberidaceae and Ranunculaceae, and single spurs occur in Papaveraceae and Ranunculaceae. The evolution of symmetry appears disconnected from changes in merism and stamen number, although monosymmetry never evolved in the context of an open ground plan. In bisexual species, monosymmetry evolved coincidently with single spurs, allowing us to propose an evolutionary scenario for Papaveraceae.

The problem of generalized flowers: morphological aspects

Since Delpino (1868–74) recognized that flowers sharing similar physiognomies are preferentially visited by certain groups of animals, it has been commonly inferred that these biological groups (flowers and pollinators) have passed a more or less complicated evolutionary process of mutual specialization. The question, however, as to what were the initial angiosperm floral forms remains unanswered. Whatever the form, a broad spectrum of visitors was likely. Each organism needs to be adapted to its environment, for which reason the term “generalized” instead of “non‐specialized” is to be preferred. Generalized flowers occur even in otherwise highly evolved families, suggesting that these representatives have developed secondarily from a somewhat specialized pollination type; this points to the fact that “generalized” and “specialized” are relative terms. It also means that a generalized flower is not synonymous with a “primitive flower”! In terms of morphology, the original “primitive flower” form is a subject of debate. Neither in the fossil records nor among extant, archaic angiosperms is there a model organism bearing a flower with a broad spectrum of visitors, and which exhibits all organs in their plesiomorphic state. Nor is it likely that such a plant will ever be discovered. Thus, we must be content with a relative solution; there is one—hitherto only one—magnolioid family, the Winteraceae, some members of which approach the idealized model. Representatives of this family are characterized by many plesiomorphic features and have open flowers visited by a broad spectrum of pollen vectors. An explanation of how these plants could have remained in this generalized condition over long time periods is offered.

Self‐pollen interference is absent in wild radish (Raphanus raphanistrum, Brassicaceae), a species with sporophytic self‐incompatibility

Explaining the diversity of mating systems and floral forms in flowering plants is a long-standing concern of evolutionary biologists. One topic of interest is the conditions under which self-pollination can interfere with seed set for flowering plants with a self-incompatibility system. We investigated the effect of self-pollen interference for wild radish, Raphanus raphanistrum, which has sporophytic self-incompatibility. We performed pollinations and determined seed set for plants grown in the greenhouse, using pollen mixtures representing either self- with outcross-pollen or outcross-pollen alone. Stigmas were collected for a subset of pollinated flowers to determine the number of pollen grains applied. Average seed set for the self/cross (5.13 seeds/pollination) and cross treatments (5.09 seeds/pollination) did not differ significantly. Stigmatic pollen loads averaged around 700 grains, an amount close to observed natural pollen loads on R. raphanistrum. We concluded that for R. raphanistrum in natural populations, self-pollen is unlikely to interfere with outcross-pollen success. This study is the first to investigate effects of self-pollen interference on seed set for a homomorphic species with sporophytic self-incompatibility where rejection occurs at the stigmatic surface.

Two-dimensional patterns of soluble proteins including three hydrolytic enzymes of mature pollen of tristylous Lythrum salicaria

Lythrum salicaria, now a widespread invasive species, exhibits tristyly, a form of heteromorphic selfincompatibility. In tristyly, each plant exhibits one (and only one) of three morphologically different floral forms. Moreover, each flower produces two types of stamens, and these two exhibit different incompatibility reactions. Differences between stamens of a single flower must be the result of epigenetic phenomena and for that reason, we performed two-dimensional gel electrophoresis (2-DE) to analyze fractions of soluble proteins derived from the pollen coat and protoplast including three hydrolytic enzymes from the six different stamen types (two from each of three floral forms). There were significant differences in the 2-D protein profiles both between pollen from the same flower and between the same type of pollen from two different flowers, in the pollen coat as well as in the protoplast extracts. In five of the six samples of pollen fractions, characteristic peptides were found. Quantitative differences between pollen from the same flower were observed in case of esterases. Furthermore, analysis of proteases and acid phosphatases revealed also qualitative differences between these enzymes in pollen from the same flower.

Distribution of Flower Morphs, Ploidy Level and Sexual Reproduction of the Invasive Weed Oxalis pes-caprae in the Western Area of the Mediterranean Region

Oxalis pes-caprae is a widespread invasive weed in regions with a Mediterranean climate. In its native habitat (southern Africa) this species has been reported as heterostylous with trimorphic flowers and a self- and morph-incompatible reproductive system. In most of the areas invaded, only a pentaploid short-styled morphotype that reproduces mainly asexually by bulbils is reported, but this has only been confirmed empirically. This study aims to analyse the floral morph proportions in a wide distribution area, test the sexual female success, and explain the causes of low sexual reproduction of this species in the western area of the Mediterranean Basin. Fifty-five populations of O. pes-caprae were sampled in the Iberian Peninsula and Morocco to evaluate the floral morph ratio and individual fruit set. In plants from a dimorphic population, hand-pollination experiments were performed to evaluate the effect of the pollen source on pollen tube growth through the style. The ploidy level and genome size of individuals of each floral morph were analysed using flow cytometry. From the populations studied 89.1 % were monomorphic, with most of them containing the short-styled (SS) floral morph, and 10.9 % were dimorphic containing long-styled (LS) and SS morphs. In some of these, isoplethy was verified but no fruit production was observed in any population. A sterile form was also recorded in several populations. Hand-pollination experiments revealed that pollen grains germinated over recipient stigmas. In intermorph crossings, pollen tubes were able to develop and fruit initiation was observed in some cases, while in intramorph pollinations, pollen tube development was sporadic and no fruit initiation was observed. All individuals within each floral form presented the same DNA ploidy level: SS plants were pentaploid and LS and the sterile form were tetraploid. The low or null sexual reproduction success of this species in the area of invasion studied seems related with the high frequency of monomorphic populations, the unequal proportion of floral morphs in dimorphic populations and the presence of different ploidy levels between SS and LS morphs. The discovery of the occurrence of an LS floral morph and a sterile form, whose invading capacity in these areas is as yet unknown, will be valuable information for management programmes.