RESUMEN
Rosa rugosa is limited in landscaping applications due to its monotonous color, especially the lack of red-flowered varieties. Comprehensive assessment of petal color diversity in R. rugosa could promote to explore the mechanism of flower color formation. In this study, the variation and diversity of petal coloring of 193 R. rugosa germplasms were assessed by chromatic values (L∗, a∗, and b∗), and then divided into seven clusters belonging to three groups with pinkish-purple (185 individuals), white (6), and red (2) petals, respectively. Total anthocyanin content was the most important factor affecting flower color diversity and red hue formation of R. rugosa petals. There were significant correlations between petal color chromatic indexes and the sum content and the ratio of two major anthocyanin, namely cyanidin 3,5-O-diglucoside (Cy3G5G), peonidin 3,5-O-diglucoside (Pn3G5G). Both high levels of Cy3G5G + Pn3G5G and Cy3G5G/Pn3G5G were necessary conditions for red phenotype formation. Five cyanidin up-stream structural genes (RrF3'H1, RrDFR1, RrANS1, RrUF3GT1, RrUF35GT1) and one cyanidin down-stream structural gene (RrCCoAOMT1) were the key indicators which contributed to Cy3G5G + Pn3G5G and Cy3G5G/Pn3G5G, respectively. Functional verification showed that overexpression of RrDFR1, combined with silent expression of RrCCoAOMT1, could make R. rugosa petals redder by increasing the levels of Cy3G5G + Pn3G5G and Cy3G5G/Pn3G5G. These results provided a robust theoretical basis for further revealing the molecular mechanism of red petals coloration in R. rugosa.
RESUMEN
PREMISE: Flower color is a primary pollinator attractant and generally adjusted to the cognitive system of the pollinators. The perception of flower color depends on the visual system of pollinators and also on environmental factors such as light conditions and the background against which flowers are displayed. METHODS: Using bee-pollinated Fabaceae species as a model, we analyzed flower color diversity and compared flower color signals considering both the standard green and the natural leaf background of two tropical seasonally dry vegetations-a mountain rupestrian grassland (campo rupestre) and a woody savanna (cerrado)-compared to a nontropical Mediterranean shrubland. RESULTS: By using natural background, bees discriminated color for 58% of the flowers in the campo rupestre and for only 43% in cerrado. Both vegetations were surpassed by 75% of bee color discrimination in Mediterranean vegetation. Chromatic contrast and purity were similar among the three vegetation types. Green contrast and brightness were similar between the tropical vegetations but differed from the Mediterranean shrubland. Green contrast differences were lost when using a standard green background, and most variables (purity, green contrast, and brightness) differed according to the background (natural or standard green) in all vegetations. CONCLUSIONS: The natural background influenced bee perception of flower color regardless of vegetation. The background of the campo rupestre promoted green contrast for flowers, ensuring flower detection by pollinators and, along with bees, may also act as a selective pressure driving the diversity of flower colors in Fabaceae species. We highlight the importance of considering the natural background coloration when analyzing flower color signals.
Asunto(s)
Flores , Polinización , Animales , Abejas , Color , Hojas de la PlantaRESUMEN
Flowering patterns are crucial to understand the dynamics of plant reproduction and resource availability for pollinators. Seasonal climate constrains flower and leaf phenology, where leaf and flower colors likely differ between seasons. Color is the main floral trait attracting pollinators; however, seasonal changes in the leaf-background coloration affect the perception of flower color contrasts by pollinators. For a seasonally dry woody cerrado community (Brazilian savanna) mainly pollinated by bees, we verified whether seasonality affects flower color diversity over time and if flower color contrasts of bee-pollinated species differ between seasons due to changes in the leaf-background coloration. For 140 species, we classified flower colors based on human-color vision, and for 99 species, we classified flower colors based on bee-color vision (spectral measurements). We described the community's flowering pattern according to the flower colors using a unique 11 years phenological database. For the 43 bee-pollinated species in which reflectance data were also available, we compared flower color diversity and contrasts against the background between seasons, considering the background coloration of each season. Flowering was markedly seasonal, peaking at the end of the dry season (September), when the highest diversity of flower colors was observed. Yellow flowers were observed all year round, whereas white flowers were seasonal, peaking during the dry season, and pink flowers predominated in the wet season, peaking in March. Bee-bluegreen flowers peaked between September and October. Flowers from the wet and dry seasons were similarly conspicuous against their corresponding background. Regardless of flowering season, the yellowish background of the dry season promoted higher flower color contrast for all flower species, whereas the greener background of the wet season promoted a higher green contrast. Temporal patterns of flower colors and color contrasts were related to the cerrado seasonality, but also to bee's activity, visual system, and behavior. Background coloration affected flower contrasts, favoring flower conspicuousness to bees according to the season. Thus, our results provide new insights regarding the temporal patterns of plant-pollinator interactions.