Major Flower Pigments Originate Different Colour Signals to Pollinators

Flower colour is mainly due to the presence and type of pigments. Pollinator preferences impose selection on flower colour that ultimately acts on flower pigments. Knowing how pollinators perceive flowers with different pigments becomes crucial for a comprehensive understanding of plant-pollinator communication and flower colour evolution. Based on colour space models, we studied whether main groups of pollinators, specifically hymenopterans, dipterans, lepidopterans and birds, differentially perceive flower colours generated by major pigment groups. We obtain reflectance data and conspicuousness to pollinators of flowers containing one of the pigment groups more frequent in flowers: chlorophylls, carotenoids and flavonoids. Flavonoids were subsequently classified in UV-absorbing flavonoids, aurones-chalcones and the anthocyanins cyanidin, pelargonidin, delphinidin, and malvidin derivatives. We found that flower colour loci of chlorophylls, carotenoids, UV-absorbing flavonoids, aurones-chalcones, and anthocyanins occupied different regions of the colour space models of these pollinators. The four groups of anthocyanins produced a unique cluster of colour loci. Interestingly, differences in colour conspicuousness among the pigment groups were almost similar in the bee, fly, butterfly, and bird visual space models. Aurones-chalcones showed the highest chromatic contrast values, carotenoids displayed intermediate values, and chlorophylls, UV-absorbing flavonoids and anthocyanins presented the lowest values. In the visual model of bees, flowers with UV-absorbing flavonoids (i.e., white flowers) generated the highest achromatic contrasts. Ours findings suggest that in spite of the almost omnipresence of floral anthocyanins in angiosperms, carotenoids and aurones-chalcones generates higher colour conspicuousness for main functional groups of pollinators.

Could the Three Be Edible and Natural Sources of Levodopa? Morphological Characterization of Three Taxa of Mucuna (Fabaceae) in Ebonyi State, Southeastern Nigeria

Background: There were reports that M. pruriens was edible and natural source of Levodopa used in the treatment of Parkinson’s disease, but the identity of the variety used for the treatment is uncertain. Hence, the present study is important to provide their diagnostic characters for further studies by prospective researchers. Methods: The qualitative study was carried out by observing and recording the features of the taxa while the quantitative was obtained as the leaflet length and width were measured using a metre rule. From each specimen, leaves were randomly selected and measured using metre rule. Standard methods were used in this study. Result: The three taxa possess trifoliate leaves in common and the flower colours are as follows: Yellow in M. flagellipes, purple in M. puriens var. pruriens and white in M. pruriens var. utilis. Testa colours are black, black and white in the M. flagellipes, M. pruriens var. pruriens and M. pruriens var. utilis, respectively. The highest average leaflet length was 17.5 recorded in M. pruriens var. pruriens while the lowest average leaflet length of 8.4 was recorded in M. pruriens var. utilis. The three taxa could be eaten based on review. Petal and testa colour could be used to distinguish the taxa studied.

Congenial in Vitro γ-Ray Induced Mutagenesis Underlying the Varied Array of Petal Colours in Chrysanthemum (Dendranthemum Grandiflorum Kitam). ‘Candid’

Chrysanthemum (Dendranthemum grandiflorum kitam.) is amongst the top ten cut flowers globally. The flower colour of ancestral species is restricted to white, yellow, and pink and is acquired from anthocyanins, carotenoids, and the dearth of both pigments, respectively. An extensive array of flower colours, like orange, dark red, purplish-red, and red, has been bred by enhancing the variety of pigments or the amalgamation of both pigments. In recent times, green-flowered cultivars having chlorophylls in their ray petals have been produced and have grown a reputation. Furthermore, violet /blue flowers have been bred via transgenic interventions. Flower colour is considered as critically acclaimed feature of any flower cultivar especially chrysanthemum. Creating newer chrysanthemum cultivars with novel features, for instance, new flower colours in a time and input optimised approach, is the eventual ambition for breeders. Exploring the molecular mechanisms that control flower pigmentation may present imperative suggestions for the rational manoeuvring of flower colour. To generate a diverse array of flower colour mutants in chrysanthemum cv. “Candid” through mutagenesis, in vitro grown micro shoots were exposed to 10, 20, 30, and 40 Gy gamma irradiation at 100 Gy per minute and were evaluated for different parameters. The rhizogenesis parameters declined with the increase in irradiation dose from 0 Gy to 40 Gy, while as, 10 Gy dose proved to record minimum decline in contrast to the control. Survival, leaf size, and the number of leaves plant− 1 after the 8th -week interval also decreased with the increasing trend of gamma irradiation dose but recorded a minimum decline in plants raised from shoots irradiated with 10 Gy gamma irradiation dose with respect to the control. Apparently, the minimum delay in the number of days to floral bud appearance took under 10 Gy compared to control. The highest number of flower colour mutants were recorded under 10 Gy (light pink, orange-pink, white and yellow). Demountable mutation frequency based on flower colour was desirable in plants irradiated with the slightest dose of 10 Gy

Painting the green canvas: how pigments produce flower colours

Flowering plants are characterized by the production of striking flower colours and these colours are primarily caused by the accumulation of pigments in cells of the floral organs. The extraordinary array of colours displayed in flowers relies on four main pigment groups: chlorophylls, carotenoids, flavonoids and betalains. With thousands of different compounds, flavonoids are the most diverse and widespread pigment group. They include coloured anthocyanins, aurones and chalcones, as well as many flavonoid compounds such as flavones and flavonols that are invisible to humans, but visible to most pollinators since they absorb ultraviolet light (UV). Flowers may exhibit homogenous colours produced by only one type of pigment or extremely complex colour patterns caused by the accumulation of several types of pigments in the same or in different floral organs. Here, we review the ecological biochemistry of pigments affecting flower colour. We also present data of flower colour variation and provide future research directions guided by the physiological functions of floral pigments.

Visibility and attractiveness of Fritillaria (Liliaceae) flowers to potential pollinators

Visual floral characters play an important role in shaping plant-pollinator interactions. The genus Fritillaria L. (Liliaceae), comprising approximately 140 species, is described as displaying a remarkable variety of flower colours and sizes. Despite this variation in visual floral traits of fritillaries, little is known about the potential role of these features in shaping plant-pollinator interactions. Here, we seek to clarify the role of visual attraction in species offering a robust food reward for pollinators early in the spring, which is the case for Fritillaria. We also searched for potential tendencies in the evolution of floral traits crucial for plant-pollinator communication. The generality of species with green and purple flowers may indicate an influence of environmental factors other than pollinators. The flowers of the studied species seem to be visible but not very visually attractive to potential pollinators. The food rewards are hidden within the nodding perianth, and both traits are conserved among fritillaries. Additionally, visual floral traits are not good predictors of nectar properties. When in the flowers, pollinators are navigated by nectar guides in the form of contrasting nectary area colouration. Flower colour does not serve as a phenotypic filter against illegitimate pollinators—red and orange bird-pollinated fritillaries are visible to bees.

Salvage of floral resources through re-absorption before flower abscission

Plants invest floral resources, including nectar and pigment, with likely consequent reproductive costs. We hypothesized that plants, whose flowers abscise with age, reabsorb nectar and pigment before abscission. This was tested with flowers of Rhododendron decorum, which has large, conspicuous white flowers that increasingly abscise corollas as flowers age. As this species is pollinated by bees, we also hypothesized that nectar concentration would be relatively high (i.e., > 30% wt/vol) and petals would contain UV-absorbing pigment. Floral nectar volume and concentration were sampled on successive days until abscission (up to ten days old, peak at five days) and for sub-sample of four-day-old flowers. Flowers just abscised were similarly sampled. Flower colours were measured using a modified camera, with recordings of spectral reflectance for abscised and open non-abscised flowers. Pigment content was summed values of red, green, blue channels of false color photos. As expected, flowers reabsorbed almost all nectar before abscission, separately reabsorbing nectar-sugar and nectar-water, and petals contained UV-absorbing pigment. However, flowers did not reabsorb pigment and nectar-concentration was < 30% wt/vol. That flowers reabsorb nectar, not pigment, remains unexplained, though possibly pigment reabsorption is uneconomical. Understanding floral resource reabsorption therefore requires determination of biochemical mechanisms, plus costs/benefits for individual plants.

Effects of viewing flowering plants on employees' wellbeing in an office-like environment

Despite the existence of plentiful studies on how plants can positively affect human wellbeing, few have focused on the potential effects of flower colours on stressed people. The present study was designed to illustrate the psychophysiological relaxation impacts of seeing purple and blue hydrangea flowers among finance workers. Thirty employees were asked to view purple, blue flowers or an empty table for 3-min, during which we measured the participants' brain activity, heart rate variability and skin conductance. We also assessed their emotions and mood states. Findings suggest that, compared with viewing the control, viewing blue and purple flowers resulted in a significant increase in alpha relative waves in the prefrontal and occipital lobes, and a significant increase in parasympathetic nervous activity. A significant increase in the sensation vote for ‘comfort', ‘relaxation' and ‘cheerfulness', as well as a dramatic improvement in the mood state was observed. The results show clear evidence for the support of the use of blue and purple flowering plants in places where comfort and calmness are required. In addition, blue flowers were more favoured and had the greatest positive effects. Results indicate that viewing flowering plants would be a promising therapeutic approach for enhancing physiological functions and improving psychological relaxation for office workers.

Australian native flower colours: does nectar reward drive bee pollinator flower preferences?

Colour is an important signal that flowering plants use to attract insect pollinators like bees. Previous research in Germany has shown that nectar volume is higher for flower colours that are innately preferred by European bees, suggesting an important link between colour signals, bee preferences and floral rewards. In Australia, flower colour signals have evolved in parallel to the Northern hemisphere to enable easy discrimination and detection by the phylogenetically ancient trichromatic visual system of bees, and native Australian bees also possess similar innate colour preferences to European bees. We measured 59 spectral signatures from flowers present at two preserved native habitats in South Eastern Australia and tested whether there were any significant differences in the frequency of flowers presenting higher nectar rewards depending upon the colour category of the flower signals, as perceived by bees. We also tested if there was a significant correlation between chromatic contrast and the frequency of flowers presenting higher nectar rewards. For the entire sample, and for subsets excluding species in the Asteraceae and Orchidaceae, we found no significant difference among colour categories in the frequency of high nectar reward. This suggests that whilst such relationships between flower colour signals and nectar volume rewards have been observed at a field site in Germany, the effect is likely to be specific at a community level rather than a broad general principle that has resulted in the common signalling of bee flower colours around the world.

Innate colour preferences of a hawkmoth depend on visual context

Solitary insects that feed on floral nectar must use innate knowledge to find their first flower. While innate preferences for flower colours are often described as fixed, species-specific traits, the nature and persistence of these preferences have been debated, particularly in relation to ontogenetic processes such as learning. Here we present evidence for a strong context-dependence of innate colour preferences in the crepuscular hawkmoth Manduca sexta . Contrary to expectations, our results show that innate colour biases shift with changes in the visual environment, namely illuminance and background. This finding reveals that innate responses might emerge from a contextual integration of sensory inputs involved in object class recognition rather than from the deterministic matching of such inputs with a fixed internal representation.