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Flowering phases and UV-reflectance properties of Crocus species. (A) Flower of the saffron crocus C. sativus in the early flowering phase with a syrphid fly, Episyrphus balteatus, targeting at the stigma. (B) The same flower in the subsequent flowering phase with a syrphid fly feeding on pollen. (C) Western honeybee, Apis mellifera, landing on a Crocus flower and targeting at the stigma. (D–G) Colour photograph and UV-photograph of violet and yellow garden crocuses.
Source publication
Most flowers display distinct colour patterns comprising two different areas. The peripheral large-area component of floral colour patterns attracts flower visitors from some distance and the central small-area component guides flower visitors towards landing sites. Whereas the peripheral colour is largely variable among species, the central colour...
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Saffron selections of Jammu and Kashmir are heterogeneous for floral characteristics which are mainly attributed to the environmental factors, though genetic factors may have role with regard to its differential characteristics across various selections found in the area. Identification of high yielding selections using the existing gene pool of sa...
Citations
... The ultraviolet bull's eye is a common and spectacular kind of anther mimicry. The UV bull's eye occurs in flowers or inflorescences with a UV-absorbing centre and a UVreflecting periphery, whilst the same flowers appear uniformly yellow to the human eye (Utech and Kawano, 1975;Lunau et al., 2016). However, the key feature eliciting bumblebee response to flowers is the bee-subjective colour contrast between the UV-absorbing centre and UV-reflecting periphery along with the higher spectral purity of the flower related to the surrounding. ...
Background and aims:
Colour pattern is a key cue of bee attraction selectively driving the appeal of pollinators. It comprises the main colour of the flower with extra fine patterns indicating a reward focal point such as nectar, nectaries, pollen, stamens, and floral guides. Such definition of floral traits' advertisement guides visitation by the insects, assuring precision in pollen gathering and deposition. The study, focused in Southwest Australian Floristic Region (SWAFR), aimed to spot bee colour patterns that are usual and unusual, missing, accomplished by mimicry of pollen and anthers; and overlapped between mimic-model species in floral mimicry cases.
Methods:
Floral colour patterns were examined by false colour photography in 55 flower species of multiple highly diverse natural plant communities in southwest Australia. False colour photography is a method to transform a UV-photo and a colour photo into a false colour photo based on trichromatic vision of bees. This method results particularly effective for rapid screening of large numbers of flowers for the presence of fine-scale bee-sensitive structures and surface roughage that are not detectable using standard spectrophotometry.
Key results:
Bee-, and bird-pollinated flowers showed expected but also some remarkable and unusual previously undetected floral colour pattern syndromes. Typical colour patterns include cases of pollen and flower mimicry and ultraviolet-absorbing targets. Among the atypical floral colour patterns are unusual white and UV-reflecting flowers of bee-pollinated plants, bicoloured floral guides, consistently occurring in Fabaceae spp., and flowers displaying a selective attractiveness to birds only. In orchids' genera (Diuris and Thelymitra) that employ floral mimicry of model species we revealed a surprising mimicry phenomenon of anthers mimicked in turn by models species.
Conclusion:
The study demonstrates the applicability of 'bee view' colour imaging for deciphering pollinator cues in a biodiverse flora with potential to be applied to other eco regions. The technique provides an exciting opportunity for indexing floral traits on a biome-scale to establish pollination drivers of ecological and evolutionary relevance.
... The ultraviolet bull's eye is a common and spectacular kind of anther mimicry. The UV bull's eye occurs in flowers or inflorescences with a UV-absorbing centre and a UVreflecting periphery, whilst the same flowers appear uniformly yellow to the human eye (Utech and Kawano, 1975;Lunau et al., 2016). However, the key feature eliciting bumblebee response to flowers is the bee-subjective colour contrast between the UV-absorbing centre and UV-reflecting periphery along with the higher spectral purity of the flower related to the surrounding. ...
A c c e p t e d M a n u s c r i p t 2 Background and Aims Colour pattern is a key cue of bee attraction selectively driving the appeal of pollinators. It comprises the main colour of the flower with extra fine patterns indicating a reward focal point such as nectar, nectaries, pollen, stamens, and floral guides. Such definition of floral traits' advertisement guides visitation by the insects, assuring precision in pollen gathering and deposition. The study, focused in Southwest Australian Floristic Region (SWAFR), aimed to spot bee colour patterns that are usual and unusual, missing, accomplished by mimicry of pollen and anthers; and overlapped between mimic-model species in floral mimicry cases. Methods Floral colour patterns were examined by false colour photography in 55 flower species of multiple highly diverse natural plant communities in southwest Australia. False colour photography is a method to transform a UV-photo and a colour photo into a false colour photo based on trichromatic vision of bees. This method results particularly effective for rapid screening of large numbers of flowers for the presence of fine-scale bee-sensitive structures and surface roughage that are not detectable using standard spectrophotometry. Key Results Bee-, and bird-pollinated flowers showed expected but also some remarkable and unusual previously undetected floral colour pattern syndromes. Typical colour patterns include cases of pollen and flower mimicry and ultraviolet-absorbing targets. Among the atypical floral colour patterns are unusual white and UV-reflecting flowers of bee-pollinated plants, bicoloured floral guides, consistently occurring in Fabaceae spp., and flowers displaying a selective attractiveness to birds only. In orchids' genera (Diuris and Thelymitra) that employ floral mimicry of model species we revealed a surprising mimicry phenomenon of anthers mimicked in turn by models species. Conclusion The study demonstrates the applicability of 'bee view' colour imaging for deciphering pollinator cues in a biodiverse flora with potential to be applied to other eco regions. The technique provides an exciting opportunity for indexing floral traits on a biome-scale to establish pollination drivers of ecological and evolutionary relevance.
... Compared to purple and white crocuses, which have bright contrasts between the corolla and stigma, most yellow saffrons have this feature. This may be an exclusive characteristic that was obtained during the evolution of the species to ensure the production of offspring (Lunau et al., 2016). With sufficient pollination, the petals of Desmodium setigerum will change from purple to white or green, and the upper petals will slowly fold down, covering the stigma and stamens. ...
Stigma color plays an important role in pollination. In nature, melon (Cucumis melo L.) stigmas are either yellow or green; however, a review of the literature found no report on how stigma color affects pollination and fruit development in melon. Here, we used an F2 melon population derived from a cross between ‘MR-1’ (P1, with green stigmas) and ‘M1-32’ (P2, with yellow stigmas), and performed genetic analysis and mapping. The results of bulked segregant analysis allowed the identification of genetic loci controlling stigma color on chromosomes 6 and 8. An F2 population consisting of 150 individuals was used for initial mapping. A genetic map of 304.17 cM was constructed using 37 cleaved amplified polymorphism sequence (CAPS) markers. We identified one major quantitative trait locus (QTL) and one minor QTL for stigma color. The major QTL GS8.1 was further mapped to a 4.13 cM interval between CAPS markers 8C-10 and 8C-16, which explained 27.04% of the phenotypic variation. In addition, GS6.1 was mapped between E-49 and 6A-7, explaining 18.6% of the phenotypic variation. This study provides a theoretical basis for the fine mapping and cloning of melon genes controlling stigma color.
... The major pollinators of Crocus spp. are bees and syrphid flies (Totland and Matthews, 1998;Lunau et al., 2016), which collect pollen and nectar (Weryszko-Chmielewska and Chwil, 2011). Floral longevity of C. discolor is ∼ 5 days (P. ...
... The flowers that are marginally covered by a tunica, consist in six tepals perigone, whose color is varying according to the genetic variability (Lunau, Konzmann, Bossems, & Harpke, 2016), three yellow stamens, and a tripartite style with three stigmas of 2-3 cm connected at the base. Stigmas, being the most valuable spice, appear as filaments of intense red color with fimbriate apical margins. ...
Crocus sativus L. (Saffron) has long been known for multiple target therapeutic uses. The plant metabolism is well investigated and the main metabolites related to saffron organoleptic qualities are crocin, crocetin, picrocrocin, and safranal. Particularly, the most abundant of them, such as crocin and safranal, are investigated for their multiple biological activities and known as potential drugs. We aimed to review the constituent features of the plant, along with its potential therapeutic effects in depression, neurodegenerative diseases, diabetes mellitus, atherosclerosis, cancer, and sexual dysfunction. A systematic literature search was conducted in PubMed, Medline, Scopus, and EMBASE, with particular attention to preclinical and clinical studies. Although saffron and its components showed potential clinical applications, further investigations are necessary to confirm the effective use of “Red Gold” and its real applications in clinical practice.
Floral colours represent a highly diverse communication signal mainly involved in flower visitors' attraction and guidance, but also flower discrimination, filtering non‐pollinators and discouraging floral antagonists. The divergent visual systems and colour preferences of flower visitors, as well as the necessity of cues for flower detection and discrimination, foster the diversity of floral colours and colour patterns. Despite the bewildering diversity of floral colour patterns, a recurrent component is a yellow UV‐absorbing floral centre, and it is still not clear why this pattern is so frequent in angiosperms. The pollen, anther, stamen, and androecium mimicry (PASAM) hypothesis suggests that the system composed of the flowers possessing such yellow UV‐absorbing floral reproductive structures, the flowers displaying central yellow UV‐absorbing structures as floral guides, and the pollen‐collecting, as well as pollen‐eating, flower visitors responding to such signals constitute the world's most speciose mimicry system. In this review, we call the attention of researchers to some hypothetical PASAM systems around the globe, presenting some fascinating examples that illustrate their huge diversity. We will also present new and published data on pollen‐eating and pollen‐collecting pollinators' responses to PASAM structures supporting the PASAM hypothesis and will discuss how widespread these systems are around the globe. Ultimately, our goal is to promote the idea that PASAM is a plausible first approach to understanding floral colour patterns in angiosperms.
Zusammenfassung: Das Farbensehen von Bienen unterscheidet sich von dem des Menschen dadurch, dass Bienen ultraviolettes Licht sehen können, aber unempfi ndlich für rotes Licht sind. Blumenfarben, die in Anpassung an Bienen als Bestäuber entstanden sind, sind nicht für das Farben-sehen des Menschen, sondern für das der Bienen gemacht. Für Bienen ist es bei der Orientierung an Blütenfarben zunächst wichtig, Blüten aus der Entfernung zu detektieren; das geschieht farbenblind vermittelt durch einen Grünkontrast der Blütenfarbe zum Hintergrund. Erst beim Näherkommen wird der Farbkontrast zum Hintergrund wichtig für Bienen. Beim Suchen einer erlernten Blütenfarbe orientieren sich Bienen vorwiegend nach dem Farbton, beim Finden neuer Blüten orientieren sich naive Bienen angeborenermaßen nach der spektralen Reinheit. Blütenfarbmuster weisen den Bie-nen den Weg zur Blütenbelohnung aus Nektar oder Pollen. Farbänderungen der Blütenkrone, der Blütenmale oder der Staubgefäße enthalten Informationen über die Belohnungsmenge. Spektrofoto-metrische Messungen von sehr kleinen Farbmusterkomponenten, Staubgefäßen oder gar einzelnen Pollenkörnern sind wegen der geringen Größe und den ungewöhnlichen Oberfl ächeneigenschaften meist nicht möglich. Mittels Falschfarbenfotografi e werden solche für Bienen sichtbare, für den Menschen unauffällige Blütensignale visualisiert. Bei der Falschfarbenfotografi e werden Ultraviolett als Blau, Blau als Grün und Grün als Rot dargestellt und Rot verworfen, sodass ein für Menschen gut interpretierbares Bild in Falschfarben entsteht, dass alle für Bienen sichtbaren Farbkomponenten enthält, aber keine Informationen, die nicht relevant sind. Durch Falschfarbenfotografi e konnte der Nachweis erbracht werden, dass für den Menschen farblich ähnliche Vogel-und Bienenblumen für Bienen gut unterscheidbar sein können, dass Glanzmuster auf Blüten als Nektarimitation dienen können, Blütenmale durch farbliche Einrahmungen für Bienen besser sichtbar sein können und dass Farb-und UV-Muster auf Blüten durch unterschiedliche Pigmente erzeugt werden. Schlüsselwörter: Blütenfarbe, Blütenfarbmuster, Bienen, Apidae, Farbensehen Summary: Colour vision in bees is different from that in humans, since bees are sensitive to ultraviolet light, but insensitive to red light. Flower colours that evolved in adaptation to bees as pollinators do not fi t colour vision in humans rather than colour vision in bees. For bees, the detection of fl owers from a distance is achieved by green contrast between fl ower and background colour, a colour-blind visual task. At close range the colour contrast against the background is important for bees. If searching for a learnt fl ower colour bees mainly orientate by means of colour hue, if searching for new fl owers naïve bees innately orientate by means of spectral purity. Floral colour patterns guide bees towards the fl oral reward, nectar or pollen. Colour changes of fl oral guides or stamens provide information about the amount of reward. Spectrophotometric measurements of very small coloured structures of fl owers like single pollen grains are not possible due to its small size and its rough surface properties. Using false colour photography small structures on fl owers that are visible for bees can be visualized. False colour photography visualizes ultraviolet as blue, blue as green, and green as red, while red is discarded. By this means, a well interpretable false colour photo can be produced that contains all relevant colour information for bees, but no additional information. By means of false colour photography evidence could be provided that bird-pollinated and bee-2 KLAUS LUNAU
Blue is a favored color of many humans. While blue skies and oceans are a common visual experience, this color is less frequently observed in flowers. We first review how blue has been important in human culture, and thus how our perception of blue has likely influenced the way of scientifically evaluating signals produced in nature, including approaches as disparate as Goethe’s Farbenlehre, Linneaus’ plant taxonomy, and current studies of plant-pollinator networks. We discuss the fact that most animals, however, have different vision to humans; for example, bee pollinators have trichromatic vision based on UV-, Blue-, and Green-sensitive photoreceptors with innate preferences for predominantly short-wavelength reflecting colors, including what we perceive as blue. The subsequent evolution of blue flowers may be driven by increased competition for pollinators, both because of a harsher environment (as at high altitude) or from high diversity and density of flowering plants (as in nutrient-rich meadows). The adaptive value of blue flowers should also be reinforced by nutrient richness or other factors, abiotic and biotic, that may reduce extra costs of blue-pigments synthesis. We thus provide new perspectives emphasizing that, while humans view blue as a less frequently evolved color in nature, to understand signaling, it is essential to employ models of biologically relevant observers. By doing so, we conclude that short wavelength reflecting blue flowers are indeed frequent in nature when considering the color vision and preferences of bees.
The colour vision system of bees and humans differs mainly in that, contrary to humans, bees are sensitive to ultraviolet light and insensitive to red light. The synopsis of a colour picture and a UV picture is inappropriate to illustrate the bee view of flowers, since the colour picture does not exclude red light. In this study false-colour pictures in bee view are assembled from digital photos taken through a UV, a blue, and a green filter matching the spectral sensitivity of the bees' photoreceptors. False-colour pictures demonstrate small-sized colour patterns in flowers, e.g. based on pollen grains, anthers, filamental hairs, and other tiny structures that are inaccessible to spectrophotometry. Moreover, false-colour pictures are suited to demonstrate flowers and floral parts that are conspicuous or inconspicuous to bees. False-colour pictures also direct the attention to other ranges of wavelength besides ultraviolet demonstrating for example blue and yellow bulls' eyes in addition to UV bulls' eyes which previously have been overlooked. False-colour photography is a robust method that can be used under field conditions, with various equipment and with simple colour editing.
Many melittophilous flowers display yellow and UV-absorbing floral guides that resemble the most common colour of pollen and anthers. The yellow coloured anthers and pollen and the similarly coloured flower guides are described as key features of a pollen and stamen mimicry system. In this study, we investigated the entire angiosperm flora of the Alps with regard to visually displayed pollen and floral guides. All species were checked for the presence of pollen- and stamen-imitating structures using colour photographs. Most flowering plants of the Alps display yellow pollen and at least 28% of the species display pollen- or stamen-imitating structures. The most frequent types of pollen and stamen imitations were (mostly yellow and UV-absorbing) colour patches on petals (65% of species displaying imitations), patterns of inflorescences (18%), stamen-like pistils (10%), and staminodes (6%), as well as three-dimensional structures such as convex lower lips and filamental hairs (<5%). Dichogamous and diclinous species display pollen- and stamen-imitating structures more often than non-dichogamous and non-diclinous species, respectively. The visual similarity between the androecium and other floral organs is attributed to mimicry, i.e. deception caused by the flower visitor’s inability to discriminate between model and mimic, sensory exploitation, and signal standardisation among floral morphs, flowering phases, and co-flowering species. We critically discuss deviant pollen and stamen mimicry concepts and evaluate the frequent evolution of pollen-imitating structures in view of the conflicting use of pollen for pollination in flowering plants and provision of pollen for offspring in bees.
