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Main conclusionPetal developmental characteristics in Fumarioideae were similar at early stages, and the specialized nectar holder/pollen container formed by the outer/inner petals. The micro-morphology of these two structures, however, shows diversity in seven species.Elaborate petals have been modified to form different types, including petal lobes, ridges, protuberances, and spurs, each with specialized functions. Nectar holder and pollen container presumably have a function in plant–pollinator interactions. In Fumarioideae, four elaborate petals of the disymmetric/zygomorphic flower present architecture forming the “nectar holder” and “pollen container” structure at the bottom and top separately. In the present study, the petals of seven species in Fumarioideae were investigated by scanning electron microscopy, light microscope, and transmission electron microscopes. The results show that petal development could divided into six stages: initiation, enlargement, adaxial/abaxial differentiation, elaborate specializations (sacs, spurs, and lobes formed), extension, and maturation, while the specialized “nectar holder” and “pollen container” structures mainly formed in stage 4. “Nectar holder” is developed from the shallow sac/spur differentiated at the base of the outer petal, eventually forming a multi-organized complex structure, together with staminal nectaries (1–2) with individual sizes. A semi-closed ellipsoidal “pollen container” is developed from the apical part of the 3-lobed inner petals fused by middle lobes and attain different sizes. The adaxial epidermis cells are specialized, with more distinct punctate/dense columnar protrusions or wavy cuticles presented on obviously thickening cell walls. In addition, a large and well-developed cavity appears between the inner and outer epidermis of the petals. As an exception, Hypecoum erectum middle lobes present stamen mimicry. Elaborate petal structure is crucial for comprehending the petal diversity in Fumarioideae and provides more evidence for further exploration of the reproductive study in Papaveraceae.

In a previous paper (Woltering and van Doorn, 1988, Journal of Experimental Botany39: 1605–1616) we identified three types of flower life cessation: by petal wilting or withering, which was either ethylene-sensitive or insensitive, and by abscission of turgid petals, which was ethylene-sensitive. These categories tended to be consistent within families. Here we re-examine these relationships by testing a further 200 species, and a number of other families. As previously, flowering shoots were exposed to 3ppm ethylene for 24h at 20°C, in darkness. Most monocotyledonous species tested showed ethylene-insensitive petal wilting, although ethylene-sensitive wilting occurred in the Alismataceae and Commelinaceae. Petals of the dicotyledonous species tested were generally sensitive to ethylene, except for a few groups showing wilting (Crassulaceae, Gentianaceae and Fumariaceae, and one subfamily in both the Ericaceae and Saxifragaceae). Petal abscission was generally ethylene-sensitive, but ethylene insensitivity was found in some Tulipa cultivars and three Saxifraga species. In most tulip cultivars tested, the petals wilted and then fell. It is concluded that (a) the response to ethylene is often consistent within either families or subfamilies; and (b) a fourth category, ethylene-insensitive petal abscission, exists both in monocotyledons and dicotyledons.

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. Mainstream views consider ancestors of Caryophyllaceae as apetalous and interpret petals as centrifugally derived staminodial appendages. This hypothesis, based on morphological similarities of petals with stamens and previous ancestral state reconstruction, is tested here. A floral developmental investigation of five species was carried out using scanning electron microscopy, combined with character optimization of the presence or absence of second-whorl petaloids. The calyx is always well developed with a quincuncial aestivation. Petaloids either develop by fractionation of common stamen-petal primordia, as in Spergularia, or petaloid development is independent and precedes alternisepalous stamens in Saponaria and Sagina. In Sagina the petaloid whorl is always fully formed but alternisepalous stamens are often reduced or missing. Petaloids are absent in Gymnocarpos and the investigated Cerastium. Developmental evidence and character mapping reject the hypothesis that petaloids represent a staminodial whorl and suggest that they are independent structures equivalent to second-whorl petals of most Pentapetalae and present in the basal Caryophyllaceae. Heterochronic shifts, including a delay in petal development and acceleration of androecial growth, are responsible for the amalgamation of petals with the androecium as common stamen-petal primordia and their appearance as stamen-derived appendages. Selective pollinator pressure in Caryophyllaceae led to variable petal expansion or reduction and loss. This trend corresponds largely with the general tendency in the core Caryophyllales for petal loss and perianth reorganization.

The chrysanthemum is widely used as a cut flower, potted flower, and garden flower worldwide and has high ornamental, edible, and medicinal value. The flower heads, composed of ray florets and disc florets, are the most diverse in terms of morphology among ornamental plants. Here, we compared and analyzed the developmental processes of different capitulum types as well as ray florets and disc florets. Morphological differentiation of the two florets occurred on the dorsal domain of the petals at stage Ⅳ of flower development, and differences in stamen development occurred at stage Ⅴ. The dorsal domain of the ray florets and the early stage of flower development were also an essential site and period, respectively, for the differences among capitulum types. In situ hybridization revealed that CmCYC2c, whose homologs are involved in the specification of floret identity in Asteraceae, was expressed in both the dorsal and ventral domains of the ray petals in the tubular-type chrysanthemum, whereas, it was differentially transcribed in the ray petals of flat- and spoon-type chrysanthemum cultivars and had lower or no expression in the dorsal domain and higher expression in the ventral domain at stage Ⅳ. Our study indicates that the expression pattern of CmCYC2c on the dorsal domain of the ray floret at stage Ⅳ contributes to the formation of diverse flower head types in chrysanthemums.

Petals are typified by their conical epidermal cells that play a predominant role for the attraction and interaction with pollinators. However, cell identities in the petal can be very diverse, with different cell types in subdomains of the petal, in different cell layers, and depending on their adaxial-abaxial or proximo-distal position in the petal. In this mini-review, we give an overview of the main cell types that can be found in the petal and describe some of their functions. We review what is known about the genetic basis for the establishment of these cellular identities and their possible relation with petal identity and polarity specifiers expressed earlier during petal development, in an attempt to bridge the gap between organ identity and cell identity in the petal.

Camellia japonica petals are colorful, rich in anthocyanins, and possess important ornamental, edible, and medicinal value. However, the regulatory mechanism of anthocyanin accumulation in C. japonica is still unclear. In this study, an integrative analysis of the metabolome and transcriptome was conducted in five C. japonica cultivars with different petal colors. Overall, a total of 187 flavonoids were identified (including 25 anthocyanins), and 11 anthocyanins were markedly differentially accumulated among these petals, contributing to the different petal colors in C. japonica . Moreover, cyanidin-3- O- (6 ″ - O- malonyl) glucoside was confirmed as the main contributor to the red petal phenotype, while cyanidin-3- O- rutinoside, peonidin-3- O- glucoside, cyanidin-3- O- glucoside, and pelargonidin-3- O- glucoside were responsible for the deep coloration of the C. japonica petals. Furthermore, a total of 12,531 differentially expressed genes (DEGs) and overlapping DEGs (634 DEGs) were identified by RNA sequencing, and the correlation between the expression level of the DEGs and the anthocyanin content was explored. The candidate genes regulating anthocyanin accumulation in the C. japonica petals were identified and included 37 structural genes (especially CjANS and Cj4CL ), 18 keys differentially expressed transcription factors (such as GATA , MYB , bHLH , WRKY , and NAC ), and 16 other regulators (mainly including transporter proteins, zinc-finger proteins, and others). Our results provide new insights for elucidating the function of anthocyanins in C. japonica petal color expression.

The wetting of rough surfaces remains a subject of active investigation by scientists. The contact angle (CA) is a traditional parameter used to characterize the hydrophobicity/philicity of a solid surface. However, it was found recently that high CAs can coexist with strong adhesion between water and a solid surface in the case of the so-called 'rose petal effect'. Several additional parameters have been proposed to characterize the interaction of water with a rough solid surface, including the CA hysteresis, the ability of water droplets to bounce off a solid surface, the tilt angle needed to initiate the flow of a droplet, and the normal and shear adhesion. It is clear now that wetting is not characterized by a single parameter, since several modes or regimes of wetting of a rough surface can exist, including the Wenzel, Cassie, lotus and petal. Understanding the wetting of rough surfaces is important in order to design non-adhesive surfaces for various applications.

Wild roses store and emit a large array of fragrant monoterpenes from their petals. Maximisation of fragrance coincides with floral maturation in many angiosperms, which enhances pollination efficiency, reduces floral predation, and improves plant fitness. We hypothesized that petal monoterpenes serve additional lifelong functions such as limiting metabolic damage from reactive oxygen species (ROS), and altering isoprenoid hormonal abundance to increase floral lifespan. Petal monoterpenes were quantified at three floral life-stages (unopened bud, open mature, and senescent) in 57 rose species and 16 subspecies originating from Asia, America, and Europe, and relationships among monoterpene richness, petal colour, ROS, hormones, and floral lifespan were analysed within a phylogenetic context. Three distinct types of petal monoterpene profiles, revealing significant developmental and functional differences, were identified: Type A, species where monoterpene abundance peaked in open mature flowers depleting thereafter; Type B, where monoterpenes peaked in senescing flowers increasing from bud stage, and a rare Type C (8 species) where monoterpenes depleted from bud stage to senescence. Cyclic monoterpenes peaked during early floral development, whereas acyclic monoterpenes (dominated by geraniol and its derivatives, often 100-fold more abundant than other monoterpenes) peaked during floral maturation in Type A and B roses. Early-diverging roses were geraniol-poor (often Type C) and white-petalled. Lifetime changes in hydrogen peroxide (H₂O₂) revealed a significant negative regression with the levels of petal geraniol at all floral life-stages. Geraniol-poor Type C roses also showed higher cytokinins (in buds) and abscisic acid (in mature petals), and significantly shorter floral lifespan compared with geraniolrich Type A and B roses. We conclude that geraniol enrichment, intensification of petal colour, and lower potential for H₂O₂-related oxidative damage characterise and likely contribute to longer floral lifespan in monoterpene-rich wild roses.

Petal color is one of the key characteristics determining the attractiveness and therefore the commercial value of an ornamental crop. Here, we present the first genome-wide association study for the important ornamental crop rose, focusing on the anthocyanin and carotenoid contents in petals of 96 diverse tetraploid garden rose genotypes. Cultivated roses display a vast phenotypic and genetic diversity and are therefore ideal targets for association genetics. For marker analysis, we used a recently designed Axiom SNP chip comprising 68,000 SNPs with additionally 281 SSRs, 400 AFLPs and 246 markers from candidate genes. An analysis of the structure of the rose population revealed three subpopulations with most of the genetic variation between individual genotypes rather than between clusters and with a high average proportion of heterozygous loci. The mapping of markers significantly associated with anthocyanin and carotenoid content to the related and genomes revealed clusters of associated markers indicating five genomic regions associated with the total anthocyanin content and two large clusters associated with the carotenoid content. Among the marker clusters associated with the phenotypes, we found several candidate genes with known functions in either the anthocyanin or the carotenoid biosynthesis pathways. Among others, we identified a glutathione-S-transferase, 4CL, an auxin response factor and F3'H as candidate genes affecting anthocyanin concentration, and CCD4 and Zeaxanthine epoxidase as candidates affecting the concentration of carotenoids. These markers are starting points for future validation experiments in independent populations as well as for functional genomic studies to identify the causal factors for the observed color phenotypes. Furthermore, validated markers may be interesting tools for marker-assisted selection in commercial breeding programmes in that they provide the tools to identify superior parental combinations that combine several associated markers in higher dosages.

Bauhinia purpurea L. is regarded as a superior plant because of the phytochemical components found in its bark, seed, leaves, and flowers. As a winter-flowering tree, B. purpurea requires the petals to be stored with intact phytochemicals in order to be available all year round. Various drying techniques were employed, such as solar drying, oven drying, and freeze drying. The dried petals was then packaged in glass bottles, plastic bags, aluminium foil bags, and plastic bottles. Fresh petals have higher concentrations of Mn, Zn), and Cu compared to N, P, K, and Mg. The oil obtained from fresh petals contained the highest concentrations of methyl cis-8,11,14-eicosatrienoate, methyl palmitoleate, and methyl arachidate, The lowest percentage peak area is seen for methyl heneicosanoate, methyl linoleate, and methyl myristoleate, which have relative peak areas of 0.91, 1.44, and 1.52%, respectively. The ethanolic extract of B. purpurea petals demonstrated greater antimicrobial activity at 20 mg concentration against S. typhi , Proteus sp., Enterobacter sp., Pseudomonas sp., and Klebsiella sp. than hexane and acetonitrile extracts. The solar-dried had greater concentrations of protein, carbohydrates, reducing sugar, carotenoid, phenol, flavonoids, antioxidants, oxalate, and tannic acid. Alkaloids and phytic acid, which are regarded as anti-nutritional, have been demonstrated to have lower values when oven-dried at 50 °C and freeze-dried at 50 °C, respectively. While the phenol, flavonoid, and carotenoid contents appeared to be higher in all dried samples, the anthocyanin concentration decreased dramatically ( p  < 0.05) in all dry samples. After analysing the stored sample for three months, it was found that most of the parameters showed a negative connection with the increased months of storage. However, solar dry sample with three months of storage showed to preserve maximum metabolite compare to all other methods. Aluminum bag packaging retained maximum content of anthocyanin, carotenoid and antioxidants.