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Simple Summary: Many plants depend on pollination by bees, whereas bees depend on flowers as food sources. Bees use a variety of floral cues such as the color, scent, or shape of the flower to find host plants. The preferred cues of honeybees and bumblebees are well studied, but the preferences of other bee species are almost unknown. Thus, we have performed behavioral experiments with artificial flowers to test whether three common bee species of the genera Lasioglossum, Bombus, and Osmia are attracted by the same or different floral cues. Our experiments showed consistent behaviors across species in experiments testing flower sizes and scent mixtures that differed in compound richness and identities. The color hue experiments, however, revealed different preferences that were probably influenced by previous foraging experience. Within colors, bee species preferred mostly intense colors that formed a high contrast to background colors. A high attractiveness of floral cues enables bees to effectively find foraging plants. With this study, we learned more about flower choice in bee species that are not used as model organisms but are important for pollination. 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. [ABSTRACT FROM AUTHOR]

Flower traits, such as flower size or color changes, can act as honest signals indicating greater rewards such as nectar; however, nothing is known about shelter-rewarding systems. Large flowers of Royal irises offer overnight shelter as a reward to Eucera bees. A black patch might signal the entrance to the tunnel (shelter) and, together with the flower size, these might act as honest signals. We hypothesize that larger flowers and black patches indicate larger tunnels, and larger tunnels will increase pollinator visits, enhancing the plants' reproductive success. We measured seven species in a controlled environment and two species from three natural populations varying in flower size. Fruit and seed sets were assessed in these natural populations. We found a positive correlation between the flower, patch size, and tunnel volume, suggesting that the flowers and patch size act as honest signals, both under controlled conditions and in the wild. However, in natural populations, this positive relationship and its effect on fitness was population-specific. Flower size increased the fitness in YER I. petrana, and interactions between flower/patch size and tunnel size increased the fitness in YER and I. atropurpurea NET populations. This suggests that the honesty of the signal is positively selected in these two populations. This study supports the hypothesis that pollinator-mediated selection leads to the honest signaling of flower advertisement. [ABSTRACT FROM AUTHOR]

The orchid market is a dynamic horticultural business in which novelty and beauty command high prices. The two main interests are the development of flowers, from the miniature to the large and showy, and their fragrance. Overall organ size might be modified by doubling the chromosome number, which can be accomplished by careful study of meiotic chromosome disjunction in hybrids or species. Meiosis is the process in which diploid (2n) pollen mother cells recombine their DNA sequences and then undergo two rounds of division to give rise to four haploid (n) cells. Thus, by interfering in chromosome segregation, one can induce the development of diploid recombinant cells, called unreduced gametes. These unreduced gametes may be used for breeding polyploid progenies with enhanced fertility and large flower size. This review provides an overview of developments in orchid polyploidy breeding placed in the large context of meiotic chromosome segregation in the model plants Arabidopsis thaliana and Brassica napus to facilitate molecular translational research and horticultural innovation. [ABSTRACT FROM AUTHOR]

Plant pathogens evade basal defense systems and attack different organs and tissues of plants. Genetic engineering of plants with genes that confer resistance against pathogens is very effective in pathogen control. Conventional breeding for disease resistance in ornamental crops is difficult and lagging relative to that in non-ornamental crops due to an inadequate number of disease-resistant genes. Therefore, genetic engineering of these plants with defense-conferring genes is a practical approach. We used rice BSR2 encoding CYP78A15 for developing transgenic Torenia fournieri Lind. lines. The overexpression of BSR2 conferred resistance against two devastating fungal pathogens, Rhizoctonia solani and Botrytis cinerea. In addition, BSR2 overexpression resulted in enlarged flowers with enlarged floral organs. Histological observation of the petal cells suggested that the enlargement in the floral organs could be due to the elongation and expansion of the cells. Therefore, the overexpression of BSR2 confers broad-spectrum disease resistance and induces the production of enlarged flowers simultaneously. Therefore, this could be an effective strategy for developing ornamental crops that are disease-resistant and economically more valuable. [ABSTRACT FROM AUTHOR]

The flower is the main organ that produces essential oils in many plants. The yield of raw flowers and the number of secretory epidermal cells are the main factors for essential oil production. The cultivated rose species "Pingyin 1" in China was used to study the effect of RrANT1 on floral organ development. Eighteen AP2 transcription factors with dual AP2 domains were identified from Rosa rugosa genome. RrANT1 belonged to euANT. The subcellular localization results showed that RrANT1 protein is localized in the nucleus. The relative expression level of RrANT1 in the receptacle is higher than that in petals in the developmental stages, and both decreased from the initial phase to senescence. Compared with the RrANT1 expression level in petals in the blooming stage, RrANT1 expression level was significant in petals (~48.8) and highest in the receptacle (~102.5) in the large bud stage. It was only highly expressed in the receptacle (~39.4) in the blooming period. RrANT1 overexpression significantly increased petunia flower and leaf sizes (~1.2), as well as flower fresh weight (~30%). The total number of epidermis cells in the petals of overexpressing plants significantly increased (>40%). This study concluded that RrANT1 overexpression can increase the size and weight of flowers by promoting cell proliferation, providing a basis for creating new rose germplasm to increase rose and essential oil yield. [ABSTRACT FROM AUTHOR]

Simple Summary: In the context of climate warming, modifications in plant pollination and reproductive success constitute a crucial issue. Modifications of both floral signals (display, size of flowers) and rewards (nectar and pollen) due to increased air temperatures may affect plant–pollinator interactions. However, relationships between modifications in floral traits and rewards caused by increased air temperatures and the associated effects on pollinator visitation rate and foraging behavior have not been thoroughly investigated. To explore the effects of temperature increase on plant–pollinator interactions, we chose the highly attractive bee-pollinated Borago officinalis and one of its pollinators, Bombus terrestris. We measured visual floral signals and rewards for plants cultivated at 21 °C or 26 °C and we investigated bumblebee behavior by tracking insect visits on plants in an indoor flight arena. Our results show that exposure to higher temperature during the flowering stages of B. officinalis negatively affects visual floral traits (e.g., by reducing the number of flowers) as well as floral rewards, affecting bumblebee visitation and foraging behavior. Bumblebees visited flowers from plants grown at 26 °C four times less frequently than they visited those from plants grown at 21 °C. Thus, the global increases in temperature caused by climate change could reduce plant pollination rates and reproductive success by reducing flower visitation. (1) Background: Plants attract pollinators using several visual signals, mainly involving the display, size, shape, and color of flowers. Each signal is relevant for pollinators foraging for floral rewards, pollen, and nectar. Changes in floral signals and rewards can be induced by an increase in temperature, drought, or other abiotic stresses and are expected to increase as global temperatures rise. In this study, we explored how pollinators respond to modified floral signals and rewards following an increase in temperature; (2) Methods: We tested the effects of warmer temperatures on bee-pollinated starflower (Borago officinalis, Boraginaceae) and determined the behavior of one of its main pollinators, the buff-tailed bumblebee (Bombus terrestris). We measured visual floral traits (display and size) and rewards (nectar and pollen) for plants cultivated at 21 °C or 26 °C. We investigated bumblebee behavior by tracking insect visits in a binary choice experiment in an indoor flight arena; (3) Results: Plants cultivated at 26 °C exhibited a smaller floral area (i.e., corolla sizes summed for all flowers per plant, 34.4 ± 2.3 cm2 versus 71.2 ± 2.7 cm2) and a greater flower height (i.e., height of the last inflorescence on the stem, 87 ± 1 cm versus 75 ± 1 cm) compared to plants grown at 21 °C. Nectar production per flower was lower in plants grown at 26 °C than in plants grown at 21 °C (2.67 ± 0.37 µL versus 4.15 ± 0.22 µL), and bumblebees visited flowers from plants grown at 26 °C four times less frequently than they visited those from plants grown at 21 °C; (4) Conclusions: These results show that warmer temperatures affect floral signals and reduce overall floral resources accessible to pollinators. Thus, the global increases in temperature caused by climate change could reduce plant pollination rates and reproductive success by reducing flower visitation. [ABSTRACT FROM AUTHOR]

Floral organ size, especially the size of the corolla, plays an important role in plant reproduction by facilitating pollination efficiency. Previous studies have outlined a hypothesized organ size pathway. However, the expression and function of many of the genes in the pathway have only been investigated in model diploid species; therefore, it is unknown how these genes interact in polyploid species. Although correlations between ploidy and cell size have been shown in many systems, it is unclear whether there is a difference in cell size between naturally occurring and synthetic polyploids. To address these questions comparing floral organ size and cell size across ploidy, we use natural and synthetic polyploids of Nicotiana tabacum (Solanaceae) as well as their known diploid progenitors. We employ a comparative transcriptomics approach to perform analyses of differential gene expression, focusing on candidate genes that may be involved in floral organ size, both across developmental stages and across accessions. We see differential expression of several known floral organ candidate genes including ARF2, BIG BROTHER, and GASA/GAST1. Results from linear models show that ploidy, cell width, and cell number positively influence corolla tube circumference; however, the effect of cell width varies by ploidy, and diploids have a significantly steeper slope than both natural and synthetic polyploids. These results demonstrate that polyploids have wider cells and that polyploidy significantly increases corolla tube circumference. [ABSTRACT FROM AUTHOR]