Fig 1 - uploaded by Casper J Van der Kooi
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Diagram of light reflection in a flower. Part of the incident light (I) is reflected by the surface (R surface ) or by the interior (R interior ), part of the light is transmitted (T) through the flower, and light of a specific wavelength range is absorbed by pigments. The light that is reflected by the surface is largely unmodulated by pigments, whereas light that is reflected by the petal interior or transmitted through the flower will be modulated by pigments inside the flower (for visualization purposes the light rays inside the flower are shown in grey).
Source publication
Background:
Flower coloration is a key enabler for pollinator attraction. Floral visual signals comprise several components that are generated by specific anatomical structures and pigmentation, and often have different functions in pollinator attraction. Anatomical studies have advanced our understanding of the optical properties of flowers, and...
Contexts in source publication
Context 1
... by floral structures and wavelength-selective absorption by pigments (Kay et al., 1981;Kevan and Backhaus, 1998;van der Kooi et al., 2016a). Backscattering of light occurs at boundaries of media with different refractive indices, such as air/cell wall or water/cell wall interfaces and cellular inhomogeneities such as (pigment) granules ( Fig. 1) (van der Kooi et al., 2016a). Flower interiors are commonly stratified, with different layers having specific scattering and pigmentation properties. For example, floral interior layers can vary in shape, size and type (e.g. mesophyll or starch cells), and pigments can be distributed throughout the flower or in specific layers (e.g. ...
Context 2
... size and type (e.g. mesophyll or starch cells), and pigments can be distributed throughout the flower or in specific layers (e.g. Kay et al., 1981;Koes et al., 1994;Kevan and Backhaus, 1998;Vignolini et al., 2012;van der Kooi et al., 2016a). Light that is not backscattered by the flower's interior or surface is transmitted through the flower (Fig. 1); transmitted light may under specific circumstances contribute to the visual signal (van der Kooi et al., ...
Context 3
... anatomy of flowers and how this shapes the visual signal is relatively little studied, leaving many questions on the evolution of the optical properties of flowers unanswered. Formation of the visual signal of a flower is always an interaction of different aspects, including scattering structures, stratification, pigment localization and pigment concentration, which each have their own level of (dis)order (Figs 1 and 3). Recent studies have started to explore how these properties contribute to the visual signal (Stavenga and van der van der Kooi et al., 2016a), but whether there are systematic differences between pollination guilds or taxonomic groups and phylogenetic constraints is virtually unstudied. ...
Citations
... Traits of animal-pollinated plant populations should respond in evolutionary time to intrinsic variation in pollinators and pollination success (Newman et al., 2014;van der Kooi et al., 2019). ...
Plant‐pollinator interactions are constrained by floral traits and available pollinators, both of which can vary across environmental gradients, with consequences for the stability of the interaction. Here, we quantified how the pollination ecology of a high‐mountain hummingbird‐pollinated plant changes across a progressively more stressful environmental gradient of the Venezuelan Andes. We compared pollination ecology between two populations of this plant: Piedras Blancas (PB) and Gavidia (GV), 4450 and 3600 m asl, respectively. We hypothesised that self‐compatibility might be higher at the higher altitude site, however we found that flowers showed similar capacities for self‐compatibility in both localities. Seed production by flowers exposed to natural pollinators was significantly higher in the lower locality, where we also found higher nectar quality, larger flowers and increased frequencies of pollinator visitations. Interestingly, the population energy offered in the nectar was the same for both localities due to the higher density and floral aggregation found in the higher altitude population. Our study demonstrates how two plant populations in different environmental conditions have different pollination ecology strategies. Pollinator visitations or their absence result in trait associations in one population that are independent in the other. These population differences are not explained by differences in pollinator assembly, but by environmental heterogeneity.
... The approximately 600 bee species in Germany [2] markedly differ regarding their phenology, nutritional needs, behavioral preferences, and lifestyles. Bee species forage on a variety of plant species and restrict their foraging based mainly on nectar and pollen properties, morphological barriers, and the abundance of plants [3]. Many bee species are specialized to specific plant taxa, whereas others are generalist flower visitors and collect pollen from a broad plant range [4]. ...
... However, in our experiments, O. bicornis clearly preferred only high contrasting colors. The results of the behavioral experiment agree with those in the literature describing the greater attraction of more highly contrasting colors for bees [3,39] Lasioglossum villosulum is described as a polylectic species, visiting different plant taxa, but the bees show strong preferences for Asteraceae and are considered to be broadly oligolectic [66,67]. When our experiments were performed, the host plant Crepis biennis (Asteraceae) was in bloom, and we observed bees visiting these flowers. ...
The interaction between bees and flowering plants is mediated by floral cues that enable bees to find foraging plants. We tested floral cue preferences among three common wild bee species: Lasioglossum villosulum, Osmia bicornis, and Bombus terrestris. Preferences are well studied in eusocial bees but almost unknown in solitary or non-eusocial generalist bee species. Using standardized artificial flowers altered in single cues, we tested preferences for color hue, achromatic contrast, scent complexity, corolla size, and flower depth. We found common attractive cues among all tested bees. Intensively colored flowers and large floral displays were highly attractive. No preferences were observed in scent complexity experiments, and the number of volatiles did not influence the behavior of bees. Differing preferences were found for color hue. The specific behaviors were probably influenced by foraging experience and depended on the flower choice preferences of the tested bee species. In experiments testing different flower depths of reward presentation, the bees chose flat flowers that afforded low energy costs. The results reveal that generalist wild bee species other than well-studied honeybees and bumblebees show strong preferences for distinct floral cues to find potential host plants. The diverse preferences of wild bees ensure the pollination of various flowering plants.
... However, few people have studied the different flower colors of I. uliginosa. Studies have shown that flowers color is mainly due to the presence of pigments (Kanehisa et al., 2008;Zhao et al., 2011;Van Der Kooi et al., 2019), and the study of impatiens color mainly focused on the anthocyanins. Therefore, we wanted to explore whether anthocyanins are the main factors affecting the formation of the four different flower colors of I. uliginosa, and whether there are other influencing factors besides anthocyanins. ...
Introduction
Flower color is one of the important ornamental traits in the plants, which plays an active role in attracting pollinators to pollinate plants and reproduce their offspring. The flower color of Impatiens uliginosa is rich, there are four main flower colors in nature: deep red, red, pink, and white. However, it remains unclear whether on four different flower colors mechanism of I. uliginosa.
Methods
We investigate colorimetric measurement, observation of epidermal cells, cellular pH determination, extraction and determination of total anthocyanins and flavonoid, semi-quantitative determination of pigment components, and gene cloning and qRT-PCR of CHS genes to study four flower colors of I. uliginosa.
Results
The L* and b* values were the highest in white flower, while the a* values were the highest in pink flower. The same shape of epidermal cells was observed in different flower colors, which was all irregular flat polygons, and there were partial lignification. Their cellular pH values were weakly acidic, while the pH values of the deep red flower was the highest and the white flower was the lowest. The highest pigment content of the four flower colors was total anthocyanin content. And malvidin-3-galactosidechloride (C23H25ClO12), cyanidin-3-O-glucoside (C21H21O11) and delphinidin (C15H11O7) were the main pigment components affecting the color of four different flower colors. The anthocyanin synthesis gene IuCHS was expressed in four flowers, and all three copies of it had the highest expression level in pink flower and the lowest expression level in white flower.
Discussion
These results revealed the influence of main internal factors on four different flower colors of I. uliginosa, and provided a basis for further understanding of the intracellular and molecular regulatory mechanisms of flower color variation, and laid a foundation for the improvement of flower color breeding of Impatiens.
... Interactions between bees and flowers are mediated by floral cues, such as colors, odors, shape, and symmetry (Faegri and van der Pijl 1979;Giurfa and Lehrer 2001;van der Kooi et al. 2016van der Kooi et al. , 2019Barragán-Fonseca et al. 2020). Among the different floral cues used by bees to locate and recognize flowers, color and odors are the most studied ones; both can be used alone or in combination (Giurfa et al. 1994;Srinivasan et al. 1998;Chittka and Raine 2006;Milet-Pinheiro et al. 2012;Dötterl and Vereecken 2010;Lawson et al. 2018;Rachersberg et al. 2019;Koethe et al. 2020). During foraging, bees frequently use visual cues to discriminate flowers with different amounts of floral resources (Wertlen et al. 2008). ...
Bees of Ptiloglossa and Xylocopa explore the chiropterophilous flowers of Pseudobombax longiflorum at twilight, but how the bees find the flowers in low light is unclear. In field experiments, we investigated if visual and olfactory floral cues are used by these bees to find P. longiflorum flowers, and which behaviors are triggered by these cues. While the crepuscular Ptiloglossa bees were more attracted to flowers with a combination of visual and olfactory cues than to isolated cues, the diurnal Xylocopa bees were equally attracted to the combination of visual and olfactory cues and to flowers with visual cues alone. Ptiloglossa bees visit the flowers under lower light intensity than Xylocopa bees. This indicates that the synergy between visual-olfactory cues facilitates flower detection in crepuscular bees. However, in higher light intensities, the large size of flowers with their broad spectrum reflectance may be enough to produce a reliable visual signal for the Xylocopa bees. Olfactory stimuli alone trigger only floral approaches in bees, while visual ones frequently trigger approaches followed by landings on flowers. This suggests that olfactory cues guide the bees to the flowers in twilight, but the presence of a visual cue is necessary to trigger landings and collection of floral resources.
Significance statement
Crepuscular and some large diurnal bees fly in the twilight and collect pollen and nectar from flowers with nocturnal anthesis. However, finding food in a dimly lit environment is not an easy task! In this study, we used a combination of visual and chemical approaches to describe, for the first time, how bees do it. We showed that although bees use olfactory and visual floral stimuli as cues, they have different strategies for finding flowers. Furthermore, olfactory and visual cues play different roles during bee foraging. Floral odors are responsible for guiding bees toward flowers in the dark, and the visual cues are responsible not only for guiding bees but also for triggering landings and floral resource collection.
... Many factors affect the optical properties of flowers for signalling(van der Kooi et al., 2019). Colour interpretation, which depends on the sensory capabilities of the visitors, may be modified by context(Garcia et al., 2020). ...
Bat pollination of Dillenia in Fiji, a genus that was presumed to be pollinated by bees, posits that other Dillenia species may be bat‐pollinated, with implications for conservation and the understanding of angiosperm evolution. Botanical descriptions of some corolla behaviours (‘falling as a whole’) suggest bat removal of permanently closed corollas, as in D. biflora. Considering the remoteness of species of interest, we reviewed some Dillenia floral traits to hypothesise what they may mean for bat pollination of the genus. We investigated D. biflora pollen grains apertures and reviewed Dillenia literature concerning corolla behaviour and colour, and pollen apertures and presentation, including pores and staminodes. Our samples had dramatically different ratios of tricolpate to tetracolpate pollen grains, a trait that does not exclude pollination by bees. Petal colour polymorphism occurs, with mixed colours proportionately less common in flowers with corollas that open. The proportion of species with staminodes did not differ between those presumed to be pollinated by bats and others, but anthers of the former were significantly more likely to have apical pores, and stamens all had similar length or were slightly longer in the middle, whereas stamens in two distinct groups occurred in 55% of bee‐pollinated species. Pollen heteromorphy may facilitate pollination by different taxa in tropical environments. However, anther apical pores and stamen uniformity are more likely to be associated with bat‐pollinated species than are other morphologies. Dillenia could be a useful model to examine evolutionary aspects of colour, heteranthery, staminodes and pollen heteromorphy. Only field work will verify bat pollination and the implications of bat dependence for Dillenia species.
... As spore propagation in myxomycetes is airflow-based [58,75], it seems unlikely that the structural coloration of the peridium serves a direct biological purpose. In contrast to flowers, where the visual appearance of petals is key for attracting pollinating insects [14,76], myxomycetes do not depend on the visual perception of peridium colors by a distributing species. Therefore, the colors more likely arise as a by-product during sporothecae maturation. ...
Brilliant colors in nature arise from the interference of light with periodic nanostructures resulting in structural color. While such biological photonic structures have long attracted interest in insects and plants, they are little known in other groups of organisms. Unexpected in the kingdom of Amoebozoa, which assembles unicellular organisms, structural colors were observed in myxomycetes, an evolutionary group of amoebae forming macroscopic, fungal-like structures. Previous work related the sparkling appearance of Diachea leucopodia to thin film interference. Using optical and ultrastructural characterization, we here investigated the occurrence of structural color across 22 species representing two major evolutionary clades of myxomycetes including 14 genera. All investigated species showed thin film interference at the peridium, producing colors with hues distributed throughout the visible range that were altered by pigmentary absorption. A white reflective layer of densely packed calcium-rich shells is observed in a compound peridium in Metatrichia vesparium, whose formation and function are still unknown. These results raise interesting questions on the biological relevance of thin film structural colors in myxomycetes, suggesting they may be a by-product of their reproductive cycle.
... The color of owers is a prominent characteristic that is highly valued by customers and also holds ecological signi cance. The composition of oral color is in uenced by various elements such as secondary metabolites in cell pigments, the shape of epidermal cells [37], the pH of cell sap [38], and mineral content [39]. The most in uential factor among them is the buildup of a certain type of pigments [40]. ...
Rose ( Rosa sp. ) is one of the most important ornamentals which is commercialize for its aesthetic values, essential oils, cosmetic, perfume, pharmaceuticals and food industries in the world. It has wide range of variations that is mostly distinguished by petal color differences which is interlinked with the phytochemicals, secondary metabolites and antinutrient properties. Here, we explored the color, bioactive compounds and antinutritional profiling and their association to sort out the most promising rose genotypes. For this purpose, we employed both quantitative and qualitative evaluation by colorimetric, spectrophotometric and visual analyses following standard protocols. The experiment was laid out in randomized complete block design (RCBD) with three replications where ten rose accessions labelled R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 were used as plant materials. Results revealed in quantitative assessment, the maximum L*, a* and b* value was recorded from rose accessions R4, R6 and R10, respectively which is further confirmed with the visually observed color of the respective rose petals. Proximate composition analyses showed that the highest amount of carotenoid and β-carotene was found in R10 rose accession, anthocyanin and betacyanin in R7. Among the bioactive compounds, maximum tocopherol, phenolic and flavonoid content was recorded in R8, R6 and R3 while R1 showed the highest free radical scavenging potentiality with the lowest IC 50 (82.60 µg/ mL FW) compared to the others. Meanwhile, the enormous variation was observed among the studied rose genotypes regarding the antinutrient contents of tannin, alkaloid, saponin and phytate whereas some other antinutrient like steroids, coumarines, quinones, anthraquinone and phlobatanin were also figured out with their presence or absence following qualitative visualization strategies. Furthermore, according to the Principal Component Analysis (PCA), correlation matrix and heatmap dendogram and cluster analysis, the ten rose accessions were grouped into three clusters where, cluster-I composed of R3, R4, R5, R8, cluster-II: R9, R10 and cluster-III: R1, R2, R6, R7 where the rose accessions under cluster III and cluster II were mostly contributed in the total variations by the studied variables. Therefore, the rose accessions R9, R10 and R1, R2, R6, R7 might be potential valuable resources of bioactive compounds for utilization in cosmetics, food coloration, and drugs synthesis which have considerable health impact.
... Flower color, size, and shape are visual cues used by pollinators to detect flowers during foraging (Dafni and Kevan 1997;van der Kooi et al. 2019). In Erodium paularense, even current ozone levels are apparently high enough to reduce petal size, modify petal reflectance, and alter the anthocyanin reflectance index therein (Prieto-Benitez et al. 2021). ...
Entomophilous plants rely on insects for pollination and consequently for reproduction. However, insect pollinators are facing multiple human‐driven pressures, from climate change to habitat loss to increased pesticide application. Anthropogenic activities have also led to critical increases in air pollution. A recent body of research focusing on the effects of air pollution on plant–pollinator interactions shows that air pollution might join the list of factors threatening insect pollination. Here, we examine the ways in which air pollution is thought to influence insect pollination, from potential mismatches between flowering and pollinator activity, to changes in pollinator attraction to flowers, to extensions in foraging periods. We consider the implications of these changes for plant reproduction and pollinator fitness and discuss how air pollutants are imperiling plant and pollinator communities. Finally, we define the questions that need to be addressed to better understand the impact of air pollution as a major driver of global change.
... F luorescence is widespread among extant plants, primarily due to the commonality of aromatic rings within organic matter, which act as fluorophores that absorb and emit light across the visible spectrum [1][2][3] . It is also believed that fluorescence in plants is also used as a visual signal to communicate with animals 4,5 . Although the importance of fluorescence in visual signaling is still under debate 2,5,6 , a number of possible roles have been suggested and are supported by empirical or experimental studies 1,7 : fluorescence signaling by flowers or pollen to attract pollinators; fluorescence signaling by ripe fruit or seeds to attract seed-dispersing mammals; fluorescence signaling by carnivorous plants to attract arthropod prey; and fluorescence signaling in senescent leaves to warn insects of chemical defenses and prevent egg-laying. ...
Fluorescence emission is common in plants. While fluorescence microscopy has been widely used to study living plants, its application in quantifying the fluorescence of fossil plants has been limited. Fossil plant fluorescence, from original fluorophores or formed during fossilization, can offer valuable insights into fluorescence in ancient plants and fossilization processes. In this work, we utilize two-photon fluorescence microspectroscopy to spatially and spectrally resolve the fluorescence emitted by amber-embedded plants, leaf compressions, and silicified wood. The advanced micro-spectroscope utilized, with its pixel-level spectral resolution and line-scan excitation capabilities, allows us to collect comprehensive excitation and emission spectra with high sensitivity and minimal laser damage to the specimens. By applying linear spectral unmixing to the spectrally resolved fluorescence images, we can differentiate between (a) the matrix and (b) the materials that comprise the fossil. Our analysis suggests that the latter correspond to durable tissues such as lignin and cellulose. Additionally, we observe potential signals from chlorophyll derivatives/tannins, although minerals may have contributed to this. This research opens doors to exploring ancient ecosystems and understanding the ecological roles of fluorescence in plants throughout time. Furthermore, the protocols developed herein can also be applied to analyze non-plant fossils and biological specimens.
... Frequency of UV reflection among categories of basic visible petal colors is shown in Figure 1. In arrangement with previously reports findings, yellow and violet flowers exhibited a particularly high probability of reflecting, while white and green flowers generally did not reflect UV [10,11]. Pollination guides usually absorbed UV regardless of their visible color. ...
... Some circumstantial evidence suggests this will prove to be true. The data of Thomphson et al. [11] show a dip at 360 nm in the absorption spectrum of the methanolic extract of the brightly reflecting petal tips of Rudbeckia hirta. By observing petals before and after extraction with methanol, we noted several brightly reflecting species which exhibited a marked decrease in reflection as a result of the extraction. ...
In addition to the floral shape and colors seen by the human eye, ultraviolet (UV) reflectance serves as a significant visual advertisement for pollinators of many blooming plant species. The interaction between flowers and pollinators is significantly influenced by plant UV patterns. It is common knowledge that many flowers have vacuolated pigments that are UV-absorbing in their petal cells. Nevertheless, the impact of UV reflection and absorption on pollinators to particular plant species hasn't been properly investigated. In this paper, the degree and pattern of UV light reflection in flowers of 240 plant species from 55 families were examined. Four levels of UV absorption and reflection were used to rank the flowers. While white and green flowers often reflect UV weakly, yellow and violet flowers have the highest likelihood of doing so. In general, pollination aids were nonreflective and independent of hue. UV reflection seems to be positively connected with flower size even though it is unrelated to floral symmetry. UV reflection is certainly present in all plant families; however, it seems to be more prevalent in some taxonomic groups. UV reflection and absorption appear to be influenced by the physical features and chemical make-up of the petals, just like other floral petals.
