Abaxial Petals Research Articles

Андромоноэция и протандрия у Oenanthe aquatica (Apiaceae)

The paper studies the synflorescence structure and flowering biology of the biennial monocarpic wetland plant Oenanthe aquatica. This species has a set of adaptations to prevent self-pollination, including generation of a pseudanthium, andromonoecy, intra- and interfloral protandry, and a specific sequence of flowering within its umbels. The synflorescence of O. aquatica is a panicle of umbels. The size of perfect and male flowers consistently decreases as the order of synflorescence axes grows. The size-related differences between perfect and staminate flowers on axes of the same branching order consist only in the length of their calyx abaxial teeth, corolla diameter, width of abaxial petals, length and width of anthers, and length and height of stylopodium. We have identified two arrangements of staminate flowers in O. aquatica: male flowers are located at the periphery or in the center of the umbellets. The share of staminate flowers in umbels increases as an axis order grows. The female phase of flowers on axes of one order occurs simultaneously within entire synflorescences with the male phase of flowers on axes of the next order, which might mean geitonogamy. Perfect flowers live for five to seven days, while staminate flowers function for no more than one day. The article contains 4 Figures, 2 Tables, 32 References. The Authors declare no conflict of interest.

Transcriptomic analysis of flower opening response to relatively low temperatures in Osmanthus fragrans

BackgroundSweet osmanthus (Osmanthus fragrans Lour.) is one of the top ten traditional ornamental flowers in China. The flowering time of once-flowering cultivars in O. fragrans is greatly affected by the relatively low temperature, but there are few reports on its molecular mechanism to date. A hypothesis had been raised that genes related with flower opening might be up-regulated in response to relatively low temperature in O. fragrans. Thus, our work was aimed to explore the underlying molecular mechanism of flower opening regulated by relatively low temperature in O. fragrans.ResultsThe cell size of adaxial and abaxial petal epidermal cells and ultrastructural morphology of petal cells at different developmental stages were observed. The cell size of adaxial and abaxial petal epidermal cells increased gradually with the process of flower opening. Then the transcriptomic sequencing was employed to analyze the differentially expressed genes (DEGs) under different number of days’ treatments with relatively low temperatures (19 °C) or 23 °C. Analysis of DEGs in Gene Ontology analysis showed that “metabolic process”, “cellular process”, “binding”, “catalytic activity”, “cell”, “cell part”, “membrane”, “membrane part”, “single-organism process”, and “organelle” were highly enriched. In KEGG analysis, “metabolic pathways”, “biosynthesis of secondary metabolites”, “plant-pathogen interaction”, “starch and sucrose metabolism”, and “plant hormone signal transduction” were the top five pathways containing the greatest number of DEGs. The DEGs involved in cell wall metabolism, phytohormone signal transduction pathways, and eight kinds of transcription factors were analyzed in depth.ConclusionsSeveral unigenes involved in cell wall metabolism, phytohormone signal transduction pathway, and transcription factors with highly variable expression levels between different temperature treatments may be involved in petal cell expansion during flower opening process in response to the relatively low temperature. These results could improve our understanding of the molecular mechanism of relatively-low-temperature-regulated flower opening of O. fragrans, provide practical information for the prediction and regulation of flowering time in O. fragrans, and ultimately pave the way for genetic modification in O. fragrans.

Inflorescence and floral traits of the Colombian species of <em>Tristerix (Loranthaceae)</em> related to hummingbird pollination

Floral diversification in Loranthaceae reaches its highest peak in the Andes. The flowers of the exclusively Andean genus Tristerix exhibit tubular and vividly coloured flowers pollinated by hummingbirds. We studied inflorescence and flower morphoanatomy of the two Colombian species, T. longebracteatus and the highly endangered T. secundus. Both species have terminal racemes with up to 26 ebracteolate flowers, of which the proximal one opens and sets fruits first. The slightly irregular calyx initiation is followed by the simultaneous initiation of petals and the successive initiation of stamens. Anthesis is fenestrate, explosive, and triggered by the tension of the style against the abaxial petals, a mode so far not reported in Loranthaceae. Anthetic petals spread symmetrically in T. longebracteatus and asymmetrically in T. secundus. Nectar is produced by a supraovarial disk and by the petal mesophyll. Floral lifespan lasts up to 20 days. The hummingbirds Eriocnemis vestita and Pterophanes cyanopterus are the likely pollinators of T. secundus. Morphological traits are inconclusive to support one of the two competing sister group relationships that involve Tristerix, as the lack of cataphylls in renewal shoots links Ligaria and Tristerix, whereas the terminal inflorescences support its relationship with Desmaria and Tupeia.

Study of petal topography of Lysimachia arvensis grown under natural conditions

The present study revealed that adaxial and abaxial petal epidermises of the blue-flowered Lysimachia arvensis consist of elongated, multi-micro-papillate cells, which may aid the rapid petal expansion. The epidermal cells are covered by a wrinkled relief, which is further ornamented by submicron features that increase in size the surface area of lobes; this may be a well-adapted mechanism of the small-sized flowers of L. arvensis with the short life span. The sculpturally increased surface area of adaxial epidermal cells of petals is expected to contribute to optical and adhesive properties, and wettability of the floral tissues. The adaxial and the abaxial petal surfaces of L. arvensis possess submicron cuticular folds, smaller than the sub-wavelength visible spectrum, which reflect radiation of shorter rather than longer wavelengths, whereas intense absorption was detected in the red spectral region. Also, three-celled capitate trichomes with a pigmented spherical head, which are densely distributed at the corolla margins of L. arvensis, may be involved in adhesive, defensive and functional properties of the floral tissues.

Sonerila bokorense (Melastomataceae), a new species from Cambodia

Sonerila bokorense, a new species of Melastomataceae from Cambodia, is described and illustrated. The new species is similar to S. calophylla, but it is distinguished by having aggregated tubercles, narrower leaves, and glandular trichomes on the pedicels, hypanthium, mid-veins of abaxial petals, and capsules.

Wax layers on Cosmos bipinnatus petals contribute unequally to total petal water resistance.

Cuticular waxes coat all primary aboveground plant organs as a crucial adaptation to life on land. Accordingly, the properties of waxes have been studied in much detail, albeit with a strong focus on leaf and fruit waxes. Flowers have life histories and functions largely different from those of other organs, and it remains to be seen whether flower waxes have compositions and physiological properties differing from those on other organs. This work provides a detailed characterization of the petal waxes, using Cosmos bipinnatus as a model, and compares them with leaf and stem waxes. The abaxial petal surface is relatively flat, whereas the adaxial side consists of conical epidermis cells, rendering it approximately 3.8 times larger than the projected petal area. The petal wax was found to contain unusually high concentrations of C(22) and C(24) fatty acids and primary alcohols, much shorter than those in leaf and stem waxes. Detailed analyses revealed distinct differences between waxes on the adaxial and abaxial petal sides and between epicuticular and intracuticular waxes. Transpiration resistances equaled 3 × 10(4) and 1.5 × 10(4) s m(-1) for the adaxial and abaxial surfaces, respectively. Petal surfaces of C. bipinnatus thus impose relatively weak water transport barriers compared with typical leaf cuticles. Approximately two-thirds of the abaxial surface water barrier was found to reside in the epicuticular wax layer of the petal and only one-third in the intracuticular wax. Altogether, the flower waxes of this species had properties greatly differing from those on vegetative organs.

Differential transcriptome analysis reveals insight into monosymmetric corolla development of the crucifer Iberis amara.

BackgroundIn the co-evolution between insects and plants, the establishment of floral monosymmetry was an important step in angiosperm development as it facilitated the interaction with insect pollinators and, by that, likely enhanced angiosperm diversification. In Antirrhinum majus, the TCP transcription factor CYCLOIDEA is the molecular key regulator driving the formation of floral monosymmetry. Although most Brassicaceae form a polysymmetric corolla, six genera develop monosymmetric flowers with two petal pairs of unequal size. In the monosymmetric crucifer Iberis amara, formation of the different petal pairs coincides with a stronger expression of the CYC-homolog IaTCP1 in the small, adaxial petals.ResultsIn this study, RNA-Seq was employed to reconstruct the petal transcriptome of the non-model species Iberis amara. About 9 Gb of sequence data was generated, processed and re-assembled into 18,139 likely Iberis unigenes, from which 15,983 showed high sequence homology to Arabidopsis proteins. The transcriptome gives detailed insight into the molecular mechanisms governing late petal development. In addition, it was used as a scaffold to detect genes differentially expressed between the small, adaxial and the large, abaxial petals in order to understand the molecular mechanisms driving unequal petal growth. Far more genes are expressed in adaxial compared to abaxial petals implying that IaTCP1 activates more genes than it represses. Amongst all genes upregulated in adaxial petals, a significantly enhanced proportion is associated with cell wall modification and cell-cell signalling processes. Furthermore, microarrays were used to detect and compare quantitative differences in TCP target genes in transgenic Arabidopsis plants ectopically expressing different TCP transcription factors.ConclusionsThe increased occurrences of genes implicated in cell wall modification and signalling implies that unequal petal growth is achieved through an earlier stop of the cell proliferation phase in the small, adaxial petals, followed by the onset of cell expansion. This process, which forms the monosymmetric corolla of Iberis amara, is likely driven by the enhanced activity of IaTCP1 in adaxial petals.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0285-4) contains supplementary material, which is available to authorized users.

A taxonomic revision of the South American papilionoid genusLuetzelburgia(Fabaceae)

A taxonomic revision of the monophyletic vataireoid genus Luetzelburgia (Fabaceae, Papilionoideae) is presented, including comments on the biogeography, phylogeny and morphological evolution derived from a combined phylogenetic analysis of morphology and seven DNA regions. The genus is characterized by the unique combination of crimped petals, sericeous on outer surface and biauriculate at the base, oblong to obovate standard petal, lateral and abaxial petals undifferentiated in shape, nearly free filaments and a samara with an indistinct endocarp, usually bearing a small wing on each side of the seed chamber. Luetzelburgia spp. are often confined to disjunct patches of South American seasonally dry tropical forests and woodlands (succulent biome). Our revision involved the examination of about 500 specimens from 56 herbaria. Species circumscription in Luetzelburgia has been a source of confusion because of the difficulty of finding complete herbarium material. All but one species was studied in the field and our extensive field work was critical for arriving at species circumscriptions that relied in large part on floral morphologies. In our revision, four names are lectotypified and one is synonymized, one species is newly described and 13 species are recognized: L. amazonica, L. andina, L. andrade-limae, L. auriculata, L. bahiensis, L. guaissara, L. guianensis, L. harleyi, L. neurocarpa, L. praecox, L. purpurea, L. sotoi and L. trialata. This revision comprises morphological descriptions and illustrations, synonymies, nomenclatural notes, phenology, phylogenetic affinities, distribution maps and preliminary conservation assessments for each species. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 328–375.

Comparative study of floral development in Onobrychis melanotricha, Hedysarum varium and Alhagi persarum (Leguminosae: Papilionoideae: Hedysareae)

Floral initiation and development of Hedysarum varium, Onobrychis melanotricha and Alhagi persarum was studied using epi-illumination light-microscopy techniques. The studied species belong to the tribe Hedysareae of the inverted repeat loss clade (IRLC clade), which is characterized by missing the large inverted repeat in the chloroplast genome. The main aim of our study was to determine developmental bases for similarities and differences among the three taxa and to verify the position of Alhagi relative to other genera of the IRLC clade. According to our observations, bracteoles are missing in Onobrychis melanotricha, but are present in the other two species. All three species share unidirectional sepal initiation starting with a median abaxial sepal and bidirectional petal initiation. Stamen initiation is unidirectional in all except in the outer stamen whorl of Hedysarum varium, where it is bidirectional. An important ontogenetic feature in O. melanotricha is the existence of five common primordia, which give rise to petal and stamen primordia. Although in H. varium and O. melanotricha common primordia are observed at some stages in floral organ initiations, in Alhagi all organs are initiated separately. Moreover, overlap in time of floral organs initiation occurs in H. varium and O. melanotricha, but not in A. persarum. The carpel initiates concurrently with the petal primordia in all. It might be presumed that Alhagi is primitive in relation to the other studied Hedysareae taxa, due to the presence of bracteoles, the absence of common primordia, and the lack of overlap in time of different organ initiations.

Floral Ontogeny in Polygalaceae and Its Bearing on the Homologies of Keeled Flowers in Fabales

Keeled flowers are characteristic of many species of Polygalaceae (tribe Polygaleae), in which there is often a distinctive crest located at the abaxial petal. This study of floral ontogeny across the entire family highlights potential suites of characters that relate to the evolution of keeled and crested flowers. One character suite encompasses interconnected transformations of the lateral perianth organs acting as an evolutionary module: bracteoles, lateral sepals (with delayed initiation and petaloid appearance), and lateral petals (suppressed or lost). The plastochron between initiation of the lateral sepals and that of the other sepals is relatively long in the tribe Polygaleae, in which the calyx is usually heteromorphic. By contrast, in the petal whorl, the difference between a zygomorphic and an actinomorphic corolla involves organ suppression rather than heterochrony. Four primary androecial patterns are identified in the family, and the gynoecium ranges between syncarpous‐bicarpellate and multicarpellate. Stigma diversity is based on two primary morphological types: one in which the papillate stigmatic surfaces lie close together, the other in which they are physically separated. The floral ontogeny of Polygalaceae is considered alongside comparative data available for other members of the order Fabales, and hypotheses to account for the similarities and differences between keeled flowers are discussed.

Production and Emission of Volatile Compounds by Petal Cells

We localized the tissues and cells that contribute to scent biosynthesis in scented and non-scented Rosa x hybrida cultivars as part of a detailed cytological analysis of the rose petal. Adaxial petal epidermal cells have a typical conical, papillate shape whereas abaxial petal epidermal cells are flat. Using two different techniques, solid/liquid phase extraction and headspace collection of volatiles, we showed that, in roses, both epidermal layers are capable of producing and emitting scent volatiles, despite the different morphologies of the cells of these two tissues. Moreover, OOMT, an enzyme involved in scent molecule biosynthesis, was localized in both epidermal layers. These results are discussed in view of results found in others species such as Antirrhinum majus, where it has been shown that the adaxial epidermis is the preferential site of scent production and emission.

Control of corolla monosymmetry in the Brassicaceae Iberis amara

Establishment of morphological novelties has contributed to the enormous diversification of floral architecture. One such novelty, flower monosymmetry, is assumed to have evolved several times independently during angiosperm evolution. To date, analysis of monosymmetry regulation has focused on species from taxa where monosymmetry prevails, such as the Lamiales and Fabaceae. In Antirrhinum majus, formation of a monosymmetric corolla is specified by the activity of the TCP transcription factors CYCLOIDEA (CYC) and DICHOTOMA (DICH). It was shown that establishment of monosymmetry likely requires an early asymmetric floral expression of CYC homologs that needs to be maintained until late floral stages. To understand how CYC homologs might have been recruited during evolution to establish monosymmetry, we characterized the likely CYC ortholog IaTCP1 from Iberis amara (Brassicaceae). Species of the genus Iberis form a monosymmetric corolla, whereas the Brassicaceae are otherwise dominated by genera developing a polysymmetric corolla. Instead of four equally sized petals, I. amara produces two small adaxial and two large abaxial petals. The timing of IaTCP1 expression differs from that of its Arabidopsis homolog TCP1 and other CYC homologs. IaTCP1 lacks an asymmetric early expression but displays a very strong differential expression in the corolla at later floral stages, when the strongest unequal petal growth occurs. Analysis of occasionally occurring peloric Iberis flower variants and comparative functional studies of TCP homologs in Arabidopsis demonstrate the importance of an altered temporal IaTCP1 expression within the Brassicaceae to govern the formation of a monosymmetric corolla.

Floral Ontogeny of Cercis (Leguminosae: Caesalpinioideae: Cercideae): Does It Show Convergence with Papilionoids?

To determine whether convergence has occurred between Cercis and papilionoid flowers, floral ontogeny of Cercis canadensis and Cercis siliquastrum was studied using scanning electron microscopy and light microscopy. In racemes, the helically arranged, acropetally initiated bracts subtend individual flowers. Paired bracteoles are initiated successively by the floral apex. Sepals are helically initiated, beginning with a single sepal in a nonmedian abaxial position. The petals initiate unidirectionally from the abaxial side, and there is overlap in time between the last sepal and the first petal. The two stamen whorls initiate unidirectionally, starting from the abaxial side. Unusual features of organ enlargement include the two abaxial petals persistently larger during development than the other three and a late‐forming hypanthium that elevates the 10 stamens attached to its rim. During receptacle expansion the two stamen whorls merge into one. Adaxially, the filament bases arch around two fenestrations, o...

Evolution and Development of Floral Diversity of Melianthaceae, an Enigmatic Southern African Family

Melianthus has strongly modified and monosymmetric (zygomorphic) flowers, and the ontogenetic derivation and evolutionary origins of these highly modified flowers are sought in a comparative study of the floral ontogeny and anatomy of two species of Melianthus and one species of Bersama. The development of monosymmetry in the family can be observed as a stepwise process linked with displacements of organ primordia and selective losses of petals and stamens. Flowers are weakly (Bersama) to strongly (Melianthus) monosymmetric. Sepal initiation is divided into two time sequences: the three outer sepals arise simultaneously with the anterior sepals behaving as a shielding unit before the two inner sepals emerge. Similarities and differences between the two genera are shown to be related to the trend to monosymmetry and are linked to specific pollination strategies. In Melianthus, an abaxial petal primordium is initiated, but it aborts at an early stage of development; in Bersama, all petals are present, but the incipient monosymmetry is visible at the onset of initiation. In Bersama, four stamens are the rule, but flowers pentamerous in all whorls are occasionally found. The nectary develops in a pouch formed between the adaxial sepal and the androecium. There is little ontogenetic evidence for a staminodial nature of the “beak” formed between the posterior stamens; it develops as a protective extension of the filament tube. A reduction sequence in the number of ovules can be seen by the progressive size limitation of the placentas. In Bersama, only one ovule arises on a marginal placenta and becomes displaced in a central position during development. The vasculature of different species is compared. The development of vascular traces is strictly linked with the initiation and external development of the floral organs. In both Melianthus and Bersama, the nectary is partly supplied by an odd adaxial trace. Our data support a relationship of Melianthaceae with Greyiaceae and Francoaceae, concordant with macromolecular results. It may be suggested that polysymmetric flowers of Bersama are secondarily derived from monosymmetric ones.

KRAMERIA (KRAMERIACEAE) FLOWERS: ORIENTATION AND ELAIOPHORE MORPHOLOGY

SummaryThe flowers of Krameria have been misunderstood since they were first described by Loefling in 1758. Some of the misconceptions about the flowers stemmed from the failure of authors to recognize the organography of the two fleshy structures which flank the ovary. Other misinterpretations resulted from confusion about the orientation of the flowers. Twice the controversy as to whether or not the flowers of Krameria species are resupinate was raised and laid to rest, but doubts still linger. Recent morphological and anatomical studies have unequivocably shown that the flowers are not resupinate and that the three small petals are adaxial. The two abaxial petals are highly modified into the two fleshy structures that have only recently been explained. Within the last five years it has been shown that these petals are glandular and play an intricate role in the pollination biology of Krameria by secreting lipids that are collected by female bees of the genus Centris (Anthophoridae). A survey of the anatomy and morphology of the glandular petals, or elaiophores, has yielded a suite of characters that are useful in showing branching patterns within the genus because they show a sequence of specializations of the outer elaiophore surface from elongate, irregular patches of secretory cells over the entire surface covered by a cuticle that separates smoothly from the cells as oils accumulate beneath it, to either small, round or polygonal patches of secretory cells over the entire surface, or to restrictions of the secretory tissue to the distal portion of the fleshy petal. The trends in specializations of the secretory surfaces of the glandular petals show correlations with trends based on sepal arrangement, degree of fusion of the superior petals, and pollen morphology.

The Genus Caylusea St. Hil. in Tropical Africa

Seeds minutely and densely tuberculate: Adaxial petals [51 7-9-lobed; abaxial petals 3-lobed; stems puberulous to pubescent; leaves linear to linear-lanceolate, acute; margin undulate, usually shortly ciliate; midrib beneath puberulous; seeds o09-1-I mm. long, pale brown when ripe, the minute tubercles not very prominent and often scarcely visible at magnifications of less than x 50 I. C. hexagyna Adaxial petals 2-3-lobed; abaxial petals simple or 2-lobed; stems pubescent; leaves lanceolate-elliptic, acute or acuminate; margin plane, glabrous; midrib beneath glabrous or sparsely puberulous; seeds