Search

The R2R3-MYB gene family represents a widely distributed class of plant transcription factors. This gene family plays an important role in many aspects of plant growth and development. However, the characterization of R2R3-MYB genes present in the genome of Coptis teeta has not been reported. Here, we describe the bioinformatic identification and characterization of 88 R2R3-MYB genes in this species, and the identification of members of the R2R3-MYB gene family in species within the order Ranales most closely related to Coptis teeta. The CteR2R3-MYB genes were shown to exhibit a higher degree of conservation compared to those of A. thaliana, as evidenced by phylogeny, conserved motifs, gene structure, and replication event analyses. Cis-acting element analysis confirmed the involvement of CteR2R3-MYB genes in a variety of developmental processes, including growth, cell differentiation, and reproduction mediated by hormone synthesis. In addition, through homology comparisons with the equivalent gene family in A. thaliana, protein regulatory network prediction and transcriptome data analysis of floral organs across three time periods of flower development, 17 candidate genes were shown to exhibit biased expression in two floral phenotypes of C. teeta. This suggests their potential involvement in floral development (anther development) in this species. [ABSTRACT FROM AUTHOR]

Trapping trichomes, a common trait found in protogynous trap flowers, are thought to enable interaction with pollinators, promoting both pollen removal and fruit set. However, this hypothesis has yet to be empirically confirmed. In this study, we experimentally tested whether trapping trichomes favour male and female functions in trap flowers. Using protogynous South American Aristolochia esperanzae trap flowers, we observed the temporal variation in both sexual functions and associated them with the wilting of the flower and trapping trichomes. Next, we described the trapping trichomes features associated with the capture, entrapment and release of pollinators. Finally, we used manipulative experiments involving trapping trichome removal to quantify their influence on pollinator entrapment, pollen removal and fruit set. While flowers wilted after the end of the female phase, the trapping trichomes only wilted some hours after pollen presentation, promoting a delay in the exit of pollinators, so they carried pollen. Trapping trichomes features, such as a density gradient towards the interior of the tube, unidirectional orientation and epicuticular waxes, may be important in the capture and entrapment of pollinators. Trapping trichome removal decreased drastically the probability of pollinator entrapment and pollen removal, leading to no fruit set. These results indicate that the evolution and maintenance of trapping trichomes in trap flowers probably occurred through selective pressures from both sexual functions and highlight their role in the functioning of this highly phenotypically specialized pollination system. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

• Pollination is essential for both fruit production as well as genetic variations. • Dichogamous nature of walnut is hindering pollination, fruit set and breeding. • Inter-specific hybrids offer considerable variations and genetic diversity. • Better understanding of pollination mechanisms can reduce PFA in walnuts. Pollination promotes both fruit production as well as genetic variations in fruit crops. Walnut belongs to the deciduous, monoecious, anemophilous and self-compatible fruit tree. Regardless of self-compatibility, due to dichogamous nature of crop it is hindering pollination, fruit set and breeding in walnut. Pollination mechanisms in walnut are not completely understood, and this unusually complex pollination behavior necessitates that we improve our mechanistic understanding of cytology, flower and pollen morphology, pollen collection, storage and germination and pollination process in walnut. A deeper understanding of pollination mechanisms is vital for fruit production as well as to reduce pistillate flower abortion (PFA) and to speed up future walnut breeding and varietal improvement by enhancing genetic diversity and developing hybrid verities targeted for having desirable traits like lateral bearing, precocity, batter fruit quality, high productivity, earlier harvest and resistance to late-spring frost, cherry leaf roll virus (CLRV), blight and pistillate flower abortion. A comprehensive grasp of walnut pollination mechanisms enables experts to offer more effective technical guidance to walnut growers. This article presents recent advancements in our understanding, consolidating pertinent and up-to-date information on walnut pollination mechanisms into a single resource for the first time. It serves as a valuable reference for researchers engaged in horticultural research, particularly in the domains of pollination, fruit production, and walnut tree breeding. [ABSTRACT FROM AUTHOR]

Spathiphyllum is a Neotropical aroid genus whose inflorescences are composed of protogynous bisexual flowers that emit strong perfumes. These scents serve as both attractants and rewards for male euglossine pollinators. We investigated the inflorescence scent of S. cannifolium, asking whether inflorescence at female and male phases differ in scent traits. For this, we collected scent samples from inflorescence at the two phases using dynamic headspace methods and analyzed them by a gas chromatograph coupled to a mass spectrometer (GC‐MS). The inflorescence scent of S. cannifolium consisted of 26 compounds, with benzyl acetate as major component (ca. 80% of the scent bouquet). We found no quantitative or qualitative differences between scents of inflorescences at female and male phases, nor in the emission time. However, when considering the timing of scent emission among individuals, we observed two general plant groups. Some individuals emitted more scent at 06:00, while others emitted more scent at 09:00, independent of the sexual phase. The similarity of floral scents between the sexes might promote floral constancy by male euglossine pollinators and consequently alternate pollinator flow between inflorescences at female and male phases. The occurrence of the two general patterns of scent emission can be interpreted as a way to ensure the pollination service. Since plants emit scents in the morning, even outside the peak emission period, this would enable these plants to attract pollinators that are active at different times than the peak emission of floral scents. This way, it would ensure the flow of pollen, even if it occurs at a low frequency. [ABSTRACT FROM AUTHOR]

Most Aristolochiaceae species studied so far are from temperate regions, bearing self‐compatible protogynous trap flowers. Although self‐incompatibility has been suggested for tropical species, the causes of self‐sterility in this family remain unknown. To fill this gap, we studied the pollination of the tropical Aristolochia esperanzae, including the physical and physiological anti‐selfing mechanisms.Floral visitors trapped inside flowers were collected to determine the pollinators. Protogyny was characterized by observing the temporal expression of sexual phases and stigmatic receptivity tests. The breeding system was investigated using hand‐pollination treatments. Pollen tube growth was observed using epifluorescence to identify the self‐incompatibility mechanism.Flies were the most frequent visitors found inside A. esperanzae trap flowers, with individuals from the family Ulidiidae being potential pollinators since they carried pollen. The characteristic flower odour and presence of larvae indicate that A. esperanzae deceives flies through oviposition‐site mimicry. Although this species showed incomplete protogyny, stigmatic receptivity decreased during the male phase, avoiding self‐pollination. Fruits developed only after cross‐ and open pollination, indicating that the population is non‐autonomous, non‐apomictic, and self‐sterile. This occurred through a delay in the growth of geitonogamous pollen tubes to the ovary and lower ovule penetration, indicating a late‐acting self‐incompatibility mechanism.Our findings expand the number of families in which late‐acting self‐incompatibility has been reported, demonstrating that it is more widespread than previously thought, especially when considering less‐studied tropical species among the basal angiosperms. [ABSTRACT FROM AUTHOR]

Key message: A relationship between vertical acropetal inflorescences with protandrous flowers and bee pollination was hypothesized by Darwin back in 1877. Here we provide empirical evidence supporting this association across the angiosperms. Plant reproduction is not only determined by flower traits but also by the arrangement of flowers within inflorescences. Based on his observations of the orchid Spiranthes autumnalis, Darwin proposed in 1877 that bee-pollinated plants presenting protandrous flowers on vertical acropetal inflorescences, where proximal flowers open first, can exploit the stereotypical foraging behavior of their pollinators (i.e., upward movement through the inflorescence) to promote pollen exportation and reduce self-pollination. In these inflorescences, male-phase flowers lie spatially above female-phase flowers. To examine this untested hypothesis, we compiled literature information from 718 angiosperms species and evaluated the association between vertical acropetal inflorescences with protandrous flowers and bee pollination within a phylogenetic comparative framework. Results reveal that this type of inflorescence is indeed more common in species pollinated by bees. Moreover, this association does not seem to be weakened by the presence of alternative self-pollination avoidance mechanisms, like self-incompatibility, suggesting that this inflorescence type benefits mainly male rather than female fitness. Other inflorescence types placing male-phase flowers above female-phase flowers, e.g., vertical basipetal inflorescences with protogynous flowers, do not provide strong evidence of a differential association with pollination by bees. Female-biased nectar production in vertical acropetal inflorescences with protandrous flowers may reinforce the behavior of bees to fly upwards, rendering Darwin's configuration more adaptive than other inflorescence configurations. [ABSTRACT FROM AUTHOR]

The article "Mechanical stimulation of the stigmas triggers switch from female to male phase in the protogynous trap flower of Aristolochia rotunda (Aristolochiaceae)" discusses the phenomenon of floral longevity and the plasticity of the female phase in dichogamous flowers. The study focuses on Aristolochia rotunda and investigates the hypothesis that the female phase is shortened after pollen deposition on the stigma. The researchers conducted experiments using hand pollination, presence of pollinators with or without pollen load, and mechanical stimulation of the stigmas. The results showed that the duration of the female phase depended on the presence of pollinators, regardless of whether they carried pollen, and that mechanical stimulation of the stigmas triggered the switch from female to male phase. The study suggests that this mechanical signal is adaptive when pollinators are limited, as it ensures the fulfillment of the flower's male function. [Extracted from the article]

The R2R3-MYB gene family represents a widely distributed class of plant transcription factors. This gene family plays an important role in many aspects of plant growth and development. However, the characterization of R2R3-MYB genes present in the genome of Coptis teeta has not been reported. Here, we describe the bioinformatic identification and characterization of 88 R2R3-MYB genes in this species, and the identification of members of the R2R3-MYB gene family in species within the order Ranales most closely related to Coptis teeta. The CteR2R3-MYB genes were shown to exhibit a higher degree of conservation compared to those of A. thaliana, as evidenced by phylogeny, conserved motifs, gene structure, and replication event analyses. Cis-acting element analysis confirmed the involvement of CteR2R3-MYB genes in a variety of developmental processes, including growth, cell differentiation, and reproduction mediated by hormone synthesis. In addition, through homology comparisons with the equivalent gene family in A. thaliana, protein regulatory network prediction and transcriptome data analysis of floral organs across three time periods of flower development, 17 candidate genes were shown to exhibit biased expression in two floral phenotypes of C. teeta. This suggests their potential involvement in floral development (anther development) in this species.

In dioecious populations, males and females may evolve different trait values to increase fitness through their respective sexual functions. Because hermaphrodites express both sexual functions, resolving sexual conflict is potentially more difficult for them. Here, we show that hermaphrodite plants can partially resolve sexual conflict by expressing different trait values in different male and female modules (e.g. different flowers, inflorescences, branches etc.). We analysed the flowering phenology, sex allocation and selection gradients on floral traits of flowers of the andromonoecious plant Pulsatilla alpina, which produces both bisexual and male flowers. Our results indicate that strong protogyny prevents early bisexual flowers from profiting from high siring opportunities early in the reproductive season at a time when male flowers could achieve high siring success. The production of unisexual male flowers thus resolves this sexual conflict because it allows the flowers to express their male function without waiting until after the female function has been performed. Our study illustrates the resolution of sexual conflict arising from phenological constraints via modular divergence in sex allocation. We discuss the extent to which modular variation in sex allocation in the context of other sexual systems may be similarly explained. [ABSTRACT FROM AUTHOR]

Floral longevity is a selected trait that shows plasticity, allowing plants to balance resource allocation and reproduction. In dichogamous flowers—in which female and male functions are decoupled in time—the duration of the female phase is expected to vary according to pollination status. We used Aristolochia rotunda as a model to test the hypothesis that the female phase should be shortened following pollen deposition on the stigma, and to identify the signal for phase switching. Aristolochia flowers are protogynous (female phase first) and trap pollinators for several days (trap flowers). The four experimental treatments we applied to flowers, i.e. hand pollination, presence of pollinators with or without pollen load in the flower, and deposition of a nylon thread on the stigma, shortened the female phase to a similar extent, demonstrating that the duration of the female phase depended on the presence of pollinators, independently of whether or not they carried pollen, and that mechanical stimulation of the stigmas was the signal for phase switching. Temperature was also shown to shorten the female stage. This mechanism of post-anthesis floral changes is original because usually such changes are triggered by chemical interactions between pollen and stigmas. We interpret the mechanical signal used in A. rotunda for phase switching to be adaptive when pollinators are limiting, because switching to the male phase even if the trapped pollinator does not bring pollen would ensure fulfilling the flower’s male function.

Many plants express their female and male sex roles at different times (dichogamy), with important consequences for mating. Dichogamy can yield mate limitation via biased floral sex ratios, particularly at the beginning and end of the flowering season when many plants simultaneously function as the same sex. This form of mate limitation should be reduced if plants adjust their allocations to female versus male sex functions in a manner that tracks seasonal variability in mating opportunities. For example, under protogyny (i.e. dichogamy with female function expressed first) plants with male-biased sex expression should have enhanced mating opportunities early in the flowering season as other plants begin to flower (in female sex phase). We quantified seasonal changes in sex allocation, patterns of mate availability and realized siring success in a population of protogynous Sagittaria latifolia. Our results were consistent with previous findings that seasonal changes in sex allocation should compensate for lost mating opportunities under the temporally variable mating environments caused by dichogamy. However, patterns of siring success in the population were inconsistent with this interpretation. We suggest that realized siring success might depend more strongly on spatial than on temporal aspects of mate availability.

In hermaphroditic dichogamous species, sporophylls are separated in time. However, the separation of sporophylls can lead to pollination inaccuracy, especially in movement-assisted dichogamy, where sporophylls alter their position over time. Is pollination inaccuracy minimised by the second sporophyll taking the exact position of the first? We address this question in Clerodendrum infortunatum, a movement-assisted dichogamous species. We made predictions from optimality arguments, and tested these by measuring sporophyll angles over time, by experimentally manipulating flowers, and by estimating correlates of the resultant fitness, taking into account pollen export, pollination inaccuracy and the resultant total pollen delivered. Contrary to expectation, anthers do not have a fixed position in the male phase, and pollination inaccuracy is high. Further, when the number of pollen grains on anthers is highest, anthers are paradoxically not positioned at the pollen export peak. Also, pollen export and pollen deposition peaks do not align. Despite this seeming maladaptiveness, the starting position of the anthers is, in fact, very close to the theoretical optimum, which results in the highest overall male fitness, measured as the total pollen delivered over the entire male phase. Instead of a simple positional exchange of sporophylls, stamens display a more complicated dynamic strategy that appears close to optimal even though naive measures of pollination inaccuracy are high. [ABSTRACT FROM AUTHOR]

●Many angiosperms are hermaphroditic and produce bisexual flowers in which male (pollen export) and female (stigma receptivity) functions are separated temporally. This sequential hermaphroditism may be associated with variation in flower size, color, or pattern, all of which may influence pollinator attraction. In this study, we describe variation in these traits across discrete functional sex stages within and between 225 greenhouse-grown individuals of Clarkia unguiculata (Onagraceae). In addition, to identify the effects of floral phenotype on pollinator attraction in this species, we examine the effects of these floral traits on pollen receipt in ~180 individuals in an experimental field array.●Petal area, ultraviolet (UV)-absorbing nectar guide area, and blue and green mean petal reflectance differ significantly across the functional sex stages of C. unguiculata. Male- and female-phase flowers display significantly different pollinator attraction traits. Petal and UV nectar guide area increase as flowers progress from male phase to female phase, while blue reflectance and green reflectance peak during anther maturation.●In field arrays of C. unguiculata, female-phase flowers with large UV nectar guides receive more pollen than those with small nectar guides, and female-phase flowers with high mean blue reflectance values are more likely to receive pollen than those with low blue reflectance. Female-phase flowers with green mean reflectance values that differ most from background foliage also receive more pollen than those that are more similar to foliage. These findings indicate that components of flower color and pattern influence pollen receipt, independent of other plant attributes that may covary with floral traits. We discuss these results in the context of hypotheses that have been proposed to explain sex-specific floral attraction traits, and we suggest future research that could improve our understanding of sexual dimorphism in sequentially hermaphroditic species and the evolution of features that promote outcrossing.

The article presents the discussion on Zuni being a new pecan (Carya illinoinensis) cultivar released and patented by the U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS). Topics include expected to perform well across all growing regions performing best in the central and western growing regions; and conducting a national pecan breeding program and releasing superior control-crossed pecan cultivars.

The article presents the discussion on Seneca being a new pecan (Carya illinoinensis) cultivar released and patented by the U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS). Topics include ‘Seneca' having a determinate pattern of growth showing a late budbreak in the spring and ceasing growth early in the autumn, indicating possible freeze tolerance and adaption in northern regions; and cold hardy trait being inherited from the two parents.

This study was carried out in the Khatam, Yazd province, Iran from the beginning of 2014 to the end of 2015. Phenological traits and pollen properties of some male pistachio genotypes ‘A1’, ‘A2’, ‘A3’, ‘A4’, ‘A5’, ‘A6’, ‘A7’, ‘A8’, ‘A9’, ‘N1’, ‘Mh1’, ‘G1’, ‘M1’, ‘M2’, and ‘F1’ were surveyed. To find the effect of pollen source on the nut traits of the resulting seeds as well as the initial fruit set, Xenia and Metaxenia were evaluated. Moreover, pistillate flowers of the ‘Akbari’ cultivar were crossed with different pollen sources. Results showed that pollen germination of male pistachio genotypes was various. Among all of the pistachio male genotypes, the highest pollen germination percentage was obtained from ‘M1’ (92.66%) followed by ‘Mh1’ (86.66%) and ‘G1’ (86.00%). There were also significant differences between cluster and pollen weight of different pollen sources. Based on our findings, among the studied genotypes, ‘M1’ had the longest pollen tube 391.6 (μm), as well as the maximum pollen tube growth rate of 39 (μm h-1). The longest flowering periods were recorded to be 10 days in ‘M1’ and 7 days in ‘Mh1’, while the shortest period was 4 days in genotype ‘A5’ and ‘A3’. A significant correlation was found between pollen grain characteristics and initial fruit set, pistachio ounce, nut blanking, and as well malformed fruits. Based on the results pollens of genotype ‘M1’ decreased the nut blanking and malformed fruits in ‘Akbari’ cultivar, pollens of genotype ‘Mh1’ improved the pistachio ounce, and genotype ‘G1’ increased the initial fruit set.

The herbaceous vine Tropaeolum pentaphyllum Lam. is a geophyte. The species presents potential use as an ornamental, food and medicinal plant. In this study, we aim to understand the reproductive biology of T. pentaphyllum in Brazilian Mixed Ombrophilous Forest, Southern Brazil. Floral structures, duration of the staminate and pistillate phases, interval between phases, overlapping of phases, breeding system were studied. Nectar volume and sugar concentration were evaluated throughout floral longevity. The floral visitor's behaviour was observed for four years, 6 am to 8 pm, totalling 100 hours of observation each year. Tropaeolum pentaphyllum is protandrous. The mean floral longevity was of 13.6 days. The duration of the staminate ( x ¯ = 6.7 days) and pistillate ( x ¯ = 6.1 days) phases did not differ. However, all flowers produced nectar in the staminate phase while just 23.3% produced in the pistillate phase. Sugar concentration remained constant over the floral longevity. Tropaeolum pentaphyllum presents mixed pollination by hummingbirds, bees and ants. Protandry, floral longevity and nectar production for up to ten days are strategies to obtain pollination and promote cross-pollination in T. pentaphyllum. The overlapping of phases (21.4%) also allows self-fertilization if cross-fertilization does not occur. These strategies can be advantageous to obtain crossbreeding and success in sexual reproduction. The longevity of flowers and standing crop of nectar show real food availability for pollinators. [ABSTRACT FROM AUTHOR]

The separation of male and female phases in hermaphroditic flowers, dichogamy, is a common occurrence that can benefit the plant through either reproductive assurance or the avoidance of selfing. When the female phase comes first, this is referred to as protogyny. One extreme form of protogyny, precocious protogyny, occurs when the stigma is presented above the apex of the bud. If such stigmas are receptive to pollen and have pollen deposited on them prior to the opening of the flower, then the precocious protogyny can be considered functional. Functional precocious protogyny was investigated in four species of sun hebes (Veronica sect. Hebe) in natural populations and in the glasshouse via observations and experiments. Three species (Veronica lavaudiana, V. maccaskillii, and V. raoulii) exhibited functional precocious protogyny, with 7–17% of deposited pollen being received and germinating while flowers were still in bud. In V. lavaudiana, both precocious stylar exsertion and a delay in the dehiscence of anthers after flower opening contributed to flowers being solely in the female phase for much of their lifespan. Sun hebes are visited by soft-wing flower beetles (Melyridae). Those with functional precocious protogyny exhibit compact inflorescences that the beetles use as walking platforms, resulting in imprecise pollination. Overall, the timing and amount of pollen deposited on stigmas within this group of sun hebes suggest that this form of pollination may have contributed to the evolution of precocious protogyny via an increase in the amount of time during which stigmas were available to receive pollen, while simultaneously reducing the amount of selfing. [ABSTRACT FROM AUTHOR]

Premise: Morphological and developmental changes as flowers age can impact patterns of mating. At the same time, direct or indirect costs of floral longevity can alter their fitness outcomes. This influence has been less appreciated, particularly with respect to the timing of selfing. We investigated changes in stigma events, autonomous selfing, outcross seed set capacity, and autofertility—a measure representing the potential for reproductive assurance—across floral lifespan in the mixed‐mating biennial Sabatia angularis. Methods: We examined stigma morphology and receptivity, autonomous self‐pollen deposition, and seed number and size under autonomous self‐pollination and hand outcross‐pollination for flowers of different ages, from 1 d of female phase until 14 d. We compared autonomous seed production to maximal outcross seed production at each flower age to calculate an index of autofertility. Results: The stigmatic lobes begin to untwist 1 d post anthesis. They progressively open, sextend, coil, and increase in receptivity, peaking or saturating at 8–11 d, depending on the measure. Autonomous seed production can occur early, but on average remains low until 6 d, when it doubles. In contrast, outcross seed number and size start out high, then decline precipitously. Consequently, autofertility increases steeply across floral lifespan. Conclusions: Changes in stigma morphology and receptivity, timing of autonomous self‐pollen deposition, and floral senescence can interact to influence the relative benefit of autonomous selfing across floral lifespan. Our work highlights the interplay between evolution of floral longevity and the mating system, with implications for the maintenance of mixed mating in S. angularis. [ABSTRACT FROM AUTHOR]

It is promising to grow the long-vegetating annual halophytes Gamanthus Bunge and Halimocnemis C.A. Mey. (Chenopodiaceae Vent.) in arid locations since they are important grazing plants for Karakol sheep and camels. These species’ xerothermic periods are when they flower and bear fruit. Research on reproductive biology must first examine how certain traits of plant reproductive organs in harsh environments relate to environmental influences. Identification of reproductive organ adaptation to air temperature and water stress in desert plants is an issue that has not received much attention from Chenopodiaceae family members. Such knowledge is crucial for developing perennial agrophytocenoses and boosting the production of pastures in need. The study of Halimocnemis species is particularly interesting since this genus is thought to be confined to the Iran-Turonian floristic zones, with the Central Asian (Turonian) plains being its center of origin. In the studied species, there are signs that ensure the xenogamous type of pollination by entomophilia. These are proterandria in flowers, brightly colored outgrowths of pollen which are secondary attractants, morning type of flowering when insects are in high flight, and autogamous type of pollination by anemophily. Similar conditions eventually lead to funneling of Halimocnemis and G. gamocarpus.

Hermaphroditism is cost‐effective because a common investment in reward and attractive structures yields benefits through both male and female reproductive success. However, the advantage is accompanied by an increased risk of self‐pollen deposition, which is generally disadvantageous. Hermaphroditic plants reduce self‐pollen deposition by separating sporophylls (a term applied to the stamens and carpels) either spatially (herkogamy) or temporally (dichogamy). In movement‐assisted dichogamy, both sporophylls show coordinated motion in opposite directions. However, the effectiveness of this movement in reducing self‐pollen deposition may be compromised at the point when the sporophylls cross each other and are close enough to interfere, resulting in a transition phase problem. The solution to this problem lies in the details of the spatiotemporal dynamics of the sporophylls in relation to their reproductive maturity. We studied these details across the floral lifetime of a protandrous shrub, Clerodendrum infortunatum (Lamiaceae), in rainforest fragments of the Western Ghats, India. We took photos of flowers at regular time intervals and measured sporophyll angles from the images. We also carried out a field experiment to determine stigma receptivity. We found that the stigma lobes remained narrowly opened at transition, and the stigma surfaces remained non‐receptive. Our findings suggest that the effectiveness of dichogamy is maximized through two properties of the transition phase: physical resistance to self‐pollen deposition by narrow stigma lobe opening and chemical non‐receptivity of the stigma during this phase. This study emphasizes the importance of accessory adaptations in movement‐assisted dichogamy to tackle the transition phase problem. [ABSTRACT FROM AUTHOR]

An increasing interest in the cultivation of (European) hazelnut (Corylus avellana) is driving a demand to breed cultivars adapted to non-conventional environments, particularly in the context of incipient climate change. Given that plant phenology is so strongly determined by genotype, a rational approach to support these breeding efforts will be to identify quantitative trait loci (QTLs) and the genes underlying the basis for adaptation. The present study was designed to map QTLs for phenology-related traits, such as the timing of both male and female flowering, dichogamy, and the period required for nuts to reach maturity. The analysis took advantage of an existing linkage map developed from a population of F1 progeny bred from the cross "Tonda Gentile delle Langhe" × "Merveille de Bollwiller," consisting in 11 LG. A total of 42 QTL-harboring regions were identified. Overall, 71 QTLs were detected, 49 on the TGdL map and 22 on the MB map; among these, 21 were classified as major; 13 were detected in at least two of the seasons (stable-major QTL). In detail, 20 QTLs were identified as contributing to the time of male flowering, 15 to time of female flowering, 25 to dichogamy, and 11 to time of nut maturity. LG02 was found to harbor 16 QTLs, while 15 QTLs mapped to LG10 and 14 to LG03. Many of the QTLs were clustered with one another. The major cluster was located on TGdL_02 and consisted of mainly major QTLs governing all the analyzed traits. A search of the key genomic regions revealed 22 candidate genes underlying the set of traits being investigated. Many of them have been described in the literature as involved in processes related to flowering, control of dormancy, budburst, the switch from vegetative to reproductive growth, or the morphogenesis of flowers and seeds. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract ●Many angiosperms are hermaphroditic and produce bisexual flowers in which male (pollen export) and female (stigma receptivity) functions are separated temporally. This sequential hermaphroditism may be associated with variation in flower size, color, or pattern, all of which may influence pollinator attraction. In this study, we describe variation in these traits across discrete functional sex stages within and between 225 greenhouse‐grown individuals of Clarkia unguiculata (Onagraceae). In addition, to identify the effects of floral phenotype on pollinator attraction in this species, we examine the effects of these floral traits on pollen receipt in ~180 individuals in an experimental field array. ●Petal area, ultraviolet (UV)‐absorbing nectar guide area, and blue and green mean petal reflectance differ significantly across the functional sex stages of C. unguiculata. Male‐ and female‐phase flowers display significantly different pollinator attraction traits. Petal and UV nectar guide area increase as flowers progress from male phase to female phase, while blue reflectance and green reflectance peak during anther maturation. ●In field arrays of C. unguiculata, female‐phase flowers with large UV nectar guides receive more pollen than those with small nectar guides, and female‐phase flowers with high mean blue reflectance values are more likely to receive pollen than those with low blue reflectance. Female‐phase flowers with green mean reflectance values that differ most from background foliage also receive more pollen than those that are more similar to foliage. These findings indicate that components of flower color and pattern influence pollen receipt, independent of other plant attributes that may covary with floral traits. We discuss these results in the context of hypotheses that have been proposed to explain sex‐specific floral attraction traits, and we suggest future research that could improve our understanding of sexual dimorphism in sequentially hermaphroditic species and the evolution of features that promote outcrossing.

An increasing interest in the cultivation of (European) hazelnut (Corylus avellana) is driving a demand to breed cultivars adapted to non-conventional environments, particularly in the context of incipient climate change. Given that plant phenology is so strongly determined by genotype, a rational approach to support these breeding efforts will be to identify quantitative trait loci (QTLs) and the genes underlying the basis for adaptation. The present study was designed to map QTLs for phenology-related traits, such as the timing of both male and female flowering, dichogamy, and the period required for nuts to reach maturity. The analysis took advantage of an existing linkage map developed from a population of F1 progeny bred from the cross “Tonda Gentile delle Langhe” × “Merveille de Bollwiller,” consisting in 11 LG. A total of 42 QTL-harboring regions were identified. Overall, 71 QTLs were detected, 49 on the TGdL map and 22 on the MB map; among these, 21 were classified as major; 13 were detected in at least two of the seasons (stable-major QTL). In detail, 20 QTLs were identified as contributing to the time of male flowering, 15 to time of female flowering, 25 to dichogamy, and 11 to time of nut maturity. LG02 was found to harbor 16 QTLs, while 15 QTLs mapped to LG10 and 14 to LG03. Many of the QTLs were clustered with one another. The major cluster was located on TGdL_02 and consisted of mainly major QTLs governing all the analyzed traits. A search of the key genomic regions revealed 22 candidate genes underlying the set of traits being investigated. Many of them have been described in the literature as involved in processes related to flowering, control of dormancy, budburst, the switch from vegetative to reproductive growth, or the morphogenesis of flowers and seeds.

The evolutionary transition from outcross- to self-fertilization is one of the most common in angiosperms and is often associated with a parallel shift in floral morphological and developmental traits, such as reduced flower size and pollen to ovule ratios, known as the "selfing syndrome." How these convergent phenotypes arise, the extent to which they are shaped by selection, and the nature of their underlying genetic basis are unsettled questions in evolutionary biology. The genus Collinsia (Plantaginaceae) includes seven independent transitions from outcrossing or mixed mating to high selfing rates accompanied by selfing syndrome traits. Accordingly, Collinsia represents an ideal system for investigating this parallelism, but requires genomic resource development. We present a high quality de novo genome assembly for the highly selfing species Collinsia rattanii. To begin addressing the basis of selfing syndrome developmental shifts, we evaluate and contrast patterns of gene expression from floral transcriptomes across three stages of bud development for C. rattanii and its outcrossing sister species Collinsia linearis. Relative to C. linearis, total gene expression is less variable among individuals and bud stages in C. rattanii. In addition, there is a common pattern among differentially expressed genes: lower expression levels that are more constant across bud development in C. rattanii relative to C. linearis. Transcriptional regulation of enzymes involved in pollen formation specifically in early bud development may influence floral traits that distinguish selfing and outcrossing Collinsia species through pleiotropic functions. Future work will include additional Collinsia outcrossing-selfing species pairs to identify genomic signatures of parallel evolution. [ABSTRACT FROM AUTHOR]

Pollen and nectar are the primary rewards offered by flowers to pollinators. In floral visitors of some plant species, pollen thieves and nectar robbers cause the reduction in pollen grain number and nectar volume, respectively. However, it remains unclear whether the absence of either of the two rewards in a given flower reduces its attraction to nectar- and pollen-collecting pollinators. We hypothesized that flowers removed of either nectar or pollen would attract fewer pollinators. We studied protandrous Impatiens oxyanthera , whose flowers provide bumblebee pollinators with both nectar and pollen in the male phase. We conducted floral reward manipulation experiments to explore how the removal of either nectar or pollen from flowers influences pollinator behaviour by comparing their visitation rates and visit duration. Compared with the control flowers, the flowers removed of pollen attracted significantly more bumblebee pollinators per 30 min, but the flowers removed of nectar or those removed of both pollen and nectar attracted significantly fewer bumblebee pollinators per 30 min. Moreover, the visit duration of bumblebee pollinators to control flowers or flowers removed of pollen was longer than that to flowers removed of nectar or those removed of both pollen and nectar. Our investigations indicated that compared with control flowers, the flowers removed of nectar attracted fewer bumblebee pollinators, supporting our hypothesis. However, our other hypothesis that pollen removal would reduce pollinator visits was not supported by our results. Instead, compared with control flowers, the flowers that contained only nectar attracted more bumblebee pollinators. Nectar seems to be the main reward, and bumblebee pollinators mainly used the absence of pollen as a visual signal to locate I. oxyanthera flowers with a potentially higher amount of nectar. [ABSTRACT FROM AUTHOR]

Duodichogamy and multi-cycle dichogamy are rare forms of temporal separation of staminate and pistillate reproductive functions in angiosperms. We studied the floral phenology, breeding system and pollination of Bridelia retusa (L.) A.Juss. and Bridelia moonii Thwaites, with a particular focus on the alternation of sexual phases to determine variation in their dichogamy. Three dichogamy patterns were identified in B. retusa, including one-cycle dichogamy (staminate ? pistillate or pistillate ? staminate), duodichogamy (staminate ? pistillate ? staminate), multi-cycle dichogamy (repeated flowering cycles alternating between staminate and pistillate) and pure staminates. Except for multi-cycle dichogamy, the other dichogamy patterns were prevalent in B. moonii. This study speculated floral mimicry system in Bridelia associated with blowflies. [ABSTRACT FROM AUTHOR]

Sexual interference between male and female function in hermaphrodite plants is reduced by protandry. In environments with insufficient pollinator service, prolongation of male function owing to limited pollen removal could restrict the duration of female function and lower seed production. We provide evidence that this form of sexual conflict has played a role in the spread of females in gynodioecious populations of Cyananthus delavayi in the pollen‐limited environments in which this subalpine species occurs. Using field experiments involving artificial pollen removal from the strongly protandrous flowers of hermaphrodites, we demonstrated a trade‐off between male‐ and female‐phase duration with no influence on overall floral longevity. Pollen removal at the beginning of anthesis resulted in hermaphrodite seed production matching that of females. In contrast, restricted pollen removal increased the duration of male function at the expense of female function lowering maternal fertility compared to females. This pattern was evident in five populations with females experiencing a twofold average seed fertility advantage compared to hermaphrodites. Gynodioecy often appears to evolve from protandrous ancestors and pollen limitation is widespread in flowering plants suggesting that sexual conflict may play an unappreciated role in the evolution of this form of sexual dimorphism. [ABSTRACT FROM AUTHOR]

Abstract Cimicifuga simplex has three genetically and ecologically distinct pollination morphs with different flowering phenology, flower sex expressions, and selfing rates. A previous study showed that strong protandry in hermaphroditic flowers of C. simplex causes there to be seasonal minority sexes; for example, unisexual female ramets are advantageous in the first half of the flowering season and bloom then (minority sex hypothesis). That study, however, did not distinguish among the three pollination morphs of C. simplex. We investigated seasonal sex ratio changes and pollinator environments of the three morphs to verify and expand the minority sex hypothesis. We investigated flowering phenology, pollinator quantity and quality, seasonal population sex ratio dynamics, and stamen/ovule ratios in hermaphroditic flowers. We also examined the seasonal female reproductive success of hermaphroditic flowers, and the effect of male flower excision on fruit set by morph II hermaphroditic flowers. Morph I (mainly hermaphroditic and female ramets) had high pollinator quality and quantity. Fruit set of hermaphroditic ramets was high throughout the flowering season. Morph II (hermaphroditic and andromonoecious ramets) had low pollinator quality, and few pollinators visited near the beginning and end of the season. Removal of male flowers led to a pollen limitation. Morph III (hermaphroditic ramets and a high selfing rate) had very low pollinator abundance throughout the flowering season, and male and female phases largely overlapped. The scarcity of male flowers in morph I is likely a result of the high pollinator quantity and quality. The high fruit set suggests that no pollen limitation existed. The low pollinator quality and quantity of the morph II population caused it to suffer from pollen limitation and may explain the absence of unisexual female ramets in this morph. The high selfing rate of morph III may be due to the extremely low pollinator abundance. Theoretical studies have indicated that the optimal investment allocation to male and female functions depends on whether a pollen limitation exists. In C. simplex, the observed relationships between pollinator environment and reproductive systems are consistent with these theoretical models.

Cimicifuga simplex has three genetically and ecologically distinct pollination morphs with different flowering phenology, flower sex expressions, and selfing rates. A previous study showed that strong protandry in hermaphroditic flowers of C. simplex causes there to be seasonal minority sexes; for example, unisexual female ramets are advantageous in the first half of the flowering season and bloom then (minority sex hypothesis). That study, however, did not distinguish among the three pollination morphs of C. simplex. We investigated seasonal sex ratio changes and pollinator environments of the three morphs to verify and expand the minority sex hypothesis. We investigated flowering phenology, pollinator quantity and quality, seasonal population sex ratio dynamics, and stamen/ovule ratios in hermaphroditic flowers. We also examined the seasonal female reproductive success of hermaphroditic flowers, and the effect of male flower excision on fruit set by morph II hermaphroditic flowers. Morph I (mainly hermaphroditic and female ramets) had high pollinator quality and quantity. Fruit set of hermaphroditic ramets was high throughout the flowering season. Morph II (hermaphroditic and andromonoecious ramets) had low pollinator quality, and few pollinators visited near the beginning and end of the season. Removal of male flowers led to a pollen limitation. Morph III (hermaphroditic ramets and a high selfing rate) had very low pollinator abundance throughout the flowering season, and male and female phases largely overlapped. The scarcity of male flowers in morph I is likely a result of the high pollinator quantity and quality. The high fruit set suggests that no pollen limitation existed. The low pollinator quality and quantity of the morph II population caused it to suffer from pollen limitation and may explain the absence of unisexual female ramets in this morph. The high selfing rate of morph III may be due to the extremely low pollinator abundance. Theoretical studies have indicated that the optimal investment allocation to male and female functions depends on whether a pollen limitation exists. In C. simplex, the observed relationships between pollinator environment and reproductive systems are consistent with these theoretical models. [ABSTRACT FROM AUTHOR]

The timing and lowering type of walnut genotypes (Juglans regia L.) is one of the important factors that lead to high and constant production. Therefore, the selection of homogame and spring frost tolerant genotypes has been among the most important priorities in breeding programs of walnut. The present paper analyzed the degree of dichogamy and the flowering time of 19 promising genotypes in walnuts from the sandy area, the S-V Oltenia region, Romania. Observations made over two calendar years have shown that the flowering period is influenced by environmental factors, especially temperature. The flowering time has changed from one year to the other, the high temperatures in spring accelerate the evolution of the male flowers,but the female flowers are not greatly influenced by these temperatures. Thus the type of flowering was not constantly, changing according to the climatic conditions of the two years. Knowing the type and timing of flowering of walnut genotypes is very important for pollination, because homogamy types are quite rare in the analyzed population.

Background and Aims To predict the evolutionary consequences of pollinator declines, we need to understand the evolution of delayed autonomous self-pollination, which is expected to evolve as a mechanism of reproductive assurance when cross-pollination becomes unreliable. This involves estimating the costs of increased levels of selfing as well as those associated with floral senescence. Methods We studied the mechanisms and costs of delayed self-pollination in the mixed-mating vine Dalechampia scandens (Euphorbiaceae) by first assessing among-population variation in herkogamy and dichogamy, which together determine the rate and timing of autonomous self-pollination. We then tested whether floral longevity responds plastically to delayed pollination. Finally, we assessed the costs of delayed self-pollination in terms of seed number and size, explicitly separating inbreeding depression from effects of floral senescence. Key Results Herkogamy varied extensively, while variation in dichogamy was more limited. Unpollinated blossoms increased their longevity, but seed quantity and quality decreased with increasing delays in pollination, independently of inbreeding depression. Conclusions In D. scandens , earlier autonomous selfing is facilitated by reduced herkogamy rather than reduced protogyny, providing reproductive assurance while maintaining the possibility for outcrossing events. Effective early autonomous self-pollination may evolve under reduced cross-pollination reliability in response to costs associated with floral senescence. [ABSTRACT FROM AUTHOR]

Heterodichogamous reproduction in plants involves two flowering morphs, reciprocal in their timing of male and female sexual functions. The degree of synchrony in floral sex phase, within and between individuals of each morph, determines the flowers’ potential fertilization partners. Complete within-morph synchrony enables across-morph mating alone, whereas unsynchronized floral sex phases may allow fertilization within a plant individual (geitonogamy) or within a morph. We documented the disruption of flowering synchrony in the heterodichogamous Ziziphus spina-christi towards the end of its seven-month flowering season. This desert tree has self-incompatible, protandrous, short-lived (2-day) flowers that open before dawn (‘Early’ morph) or around noon (‘Late’ morph). We counted flowers in the male and female phase on flowering branches that were sampled monthly during the 2016–2018 flowering seasons. In 2018, we also tagged flowers and followed their sex-phase distributions over two days at the start, middle, and end of the season. The switch to the female phase was delayed at the end-season (November-December), and 74% of the flowers did not develop beyond their male phase. Differences in male-phase duration resulted in asynchrony among flowers within each tree and among trees of both flowering morphs. Consequently, fertilization between trees of the same morph becomes potentially possible during the end-season. In controlled hand-pollination assays, some within-morph fertilizations set fruit. The end-season breakdown of synchronous flowering generates variability within morphs and populations. We suggest that this variability may potentially enable new mating combinations in a population and enhance its genetic diversity.

The flowering, nectar production and sugar content were examined in 2012–2013 seasons for three Campanula species (C. persicifolia L., C. glomerata L., C. trachelium L.). The flowers of all studied Campanula spp. are distinctly protandrous; most of them opened between 10.00 and 14.00; only the flowers of C. glomerata continued the opening process until 16.00 (GMT + 2 h). The flower life-span differed between species and was the longest for C. persicifolia – ca. 5.5 days and lasted 3.0–3.5 days in C. glomerata and C. trachelium. The duration of the male phase was 2–3 fold shorter (C. persicifolia and C. glomerata) than the female phase or was equal (C. trachelium). Irrespective of the year of study and the species, the female-biased nectar production pattern was evidenced. The amount of nectar accumulated at the female phase reached 70–87% of the maximum nectar produced by a flower. The total sugar yield (0.4– 12.2 g/10 m2) established for the studied species is low compared to other herbaceous meadow species. However, due to diverse insect visitors groups, the Campanula flowers can be recommended to support pollinators in home gardens or on idle lands.

Nectar secretion was noted both in the male and female floral phases of the protandrous flowers of Campanula patula (Campanulaceae). Female-biased sugar accumulation was evidenced and plasticity in the duration of sexual phases observed. Flowers in the male phase produced twofold less nectar with lower sugar concentrations compared to female-phase flowers. The sugar mass content averaged 0.6 mg ±0.45 SD per flower in the male phase and 1.4 ±0.5 SD per flower in the female phase. The pollen mass averaged 0.16 mg ±0.10 SD per flower. An understanding of the evolution of functional relationships between floral sexes requires consideration of the compensation of the reproductive costs, including the plastic response to interdependent factors, i.e., photosynthesis and growth, the effect of pollinators, pollen robbers, and external environmental forces.

The data of literary sources concerning the bloom of angiosperm plants and deviation in the development of a flower and inflorescence, in particular untimely flowering, was generalized; our observation results of some peculiarities of re-bloom of woody plants in the National Dendrological Park “Sofiyivka” of NAS of Ukraine (NDP “Sofiyivka”) were discussed. The flowering process was formed during a long-term evolution of a propagation system of angiosperm plants as a basis of fertilization and further fruit and seed development. As a result of vernalization and photoperiodism reactions, flowering (under regular conditions) occurs in the most favorable period for pollination and fertilization of every plant. However, various deviations, in particular, the untimely (most frequently double, sometimes three- and four-fold) flowering occurs in this perfect process of generative organ formation of angiosperm plants. An increased number of reports about re-bloom (at the end of summer – at the beginning of fall) of the representatives of various woody plant species whose flowers usually blossom in May-June prompts the analysis of the available information concerning the mechanisms of flowering and the causes which lead to deviation of flowering processes. Flowering of the woody plant representatives of the collection fund of the NDP “Sofiyivka” was studied; statistics about re-bloom in different cities of Ukraine were monitored. The classification of re-bloom facts was carried out according to V.L. Vitkovskiy (1984). Although this classification has mostly a stated nature, it was good enough when being formulated and, with certain conditions, it can be applied nowadays. Accordingly, using this classification, abnormal cases can include facts of early summer-fall flowering and early winter flowering. A late spring flowering can be adaptive response of damaged plants to exogenous stresses, due to which the probability of sexual propagation remains. Early spring-early summer flowering is a dual-natured category which, under certain conditions, may have adaptive meaning and facilitate seminal propagation. Most cases of untimely flowering registered in NDP “Sofiyivka” represent a group of early summer-fall flowering, in some cases late spring flowering occurred though. Secondary flowering is usually connected with meteorological peculiarities of the year. Most frequently it is seen in very dry years, first of all, after hot and dry spring. The rebloom can have an adaptive nature in case of development seeds with full germination, moreover the immature germs of underdeveloped seeds formed from the flowers of early summer-fall flowering can be used in breeding programs.

Many plants express their female and male sex roles at different times (dichogamy), with important consequences for mating. Dichogamy can yield mate limitation via biased floral sex ratios, particularly at the beginning and end of the flowering season when many plants simultaneously function as the same sex. This form of mate limitation should be reduced if plants adjust their allocations to female versus male sex functions in a manner that tracks seasonal variability in mating opportunities. For example, under protogyny (i.e. dichogamy with female function expressed first) plants with male-biased sex expression should have enhanced mating opportunities early in the flowering season as other plants begin to flower (in female sex phase). We quantified seasonal changes in sex allocation, patterns of mate availability and realized siring success in a population of protogynous Sagittaria latifolia . Our results were consistent with previous findings that seasonal changes in sex allocation should compensate for lost mating opportunities under the temporally variable mating environments caused by dichogamy. However, patterns of siring success in the population were inconsistent with this interpretation. We suggest that realized siring success might depend more strongly on spatial than on temporal aspects of mate availability., Competing Interests: We declare no competing interests., (© 2023 The Authors.)

The benefits of self-fertilization can vary across environments, leading to selection for different reproductive strategies and influencing the evolution of floral traits. Although stressful conditions have been suggested to favour self-pollination, the role of climate as a driver of mating-system variation is generally not well understood. Here, we investigate the contributions of local climate to intraspecific differences in mating-system traits in Clarkia pulchella Pursh in a common-garden growth chamber experiment. We also tested for plastic responses to soil moisture with watering treatments. Herkogamy (anther-stigma spacing) correlated positively with dichogamy (timing of anther-stigma receptivity) and date of first flower, and northern populations had smaller petals and flowered earlier in response to experimental drought. Watering treatment alone had little effect on traits, and dichogamy unexpectedly decreased with annual precipitation. Populations also differed in phenological response to watering treatment, based on precipitation and winter temperature of their origin, indicating that populations from cool and dry sites have greater plasticity under different levels of moisture stress. While some variation in floral traits is attributable to climate, further investigation into variation in pollinator communities and the indirect effects of climate on mating system can improve our understanding of the evolution of plant mating. [ABSTRACT FROM AUTHOR]

Abstract: Mixed mating and variation in outcrossing rate among populations of the same species are common. Outcrossing can be affected by pollinator activity and floral traits that facilitate or impede autonomous self‐fertilization. However, the relative contribution of pollen limitation and evolved differences in the ability to self‐fertilize to variation in the mating system is poorly understood and can only be disentangled using an experimental approach. We placed arrays of plants from eight Campanula americana populations that varied in autonomous selfing ability (hereafter “autonomy”) in sun and shade habitats to create high‐ and low‐pollination environments. Floral visitors were observed and pollen limitation, dichogamy, herkogamy and pollen persistence within the flower were measured. Outcrossing rate was estimated for a subset of the arrays. Pollen limitation was over three times higher in the shade than the sun due to differences in pollinator visitation. Populations with high levels of autonomy displayed greater pollen persistence and dichogamy in the more pollen‐limited environments than in the high‐pollination environments. In these high‐autonomy populations, outcrossing rates were tightly associated with pollen limitation, with reduced outcrossing under strong pollen limitation. In contrast, populations with intermediate autonomy levels had less plastic floral traits and their outcrossing rates changed little with pollen limitation. Mating system was shaped by both the pollination environment and the magnitude of plasticity in floral traits. The experimental approach used here revealed that plasticity in floral traits provides the ability to adjust mating system in response to limited potential for outcrossing. The lack of plasticity in some populations could explain mismatches between pollinator activity and mating system in natural populations. Finally, flexibility in the mating system may help explain the prevalence of mixed mating. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Background: Autonomous selfing can be favoured by reduced floral herkogamy, dichogamy and pollinator visitation. Autonomous selfing diminishes as pollinator abundance increases; however, the ways pollinators contribute to such result have not been tested. Pollinators can reduce the occurrence of autonomous selfing by two not mutually exclusive mechanisms: successful pollen deposition on stigmas and pollen removal from anthers. Aims: We tested the role of herkogamy and protandry on autonomous selfing and the role of pollinators to reduce it via pollen removal. Methods: We studied Lepechinia floribunda (Lamiaceae) in two natural populations in the Chaco Serrano forest, Argentina. Pollination treatments were conducted to test if floral herkogamy and pollen removal by one pollinator visitation decreased seed set by autonomous selfing. Results: Seed set in pollinator exclusion and emasculation treatments were higher in flowers with lack of herkogamy and selfing increased seed set only in these flowers. Pollen removal during the male phase decreased by 72% the probability of autonomous self-pollination. Conclusions: Flowers with lack of herkogamy are reproductively more advantageous than flowers with approach herkogamy independently of pollinator abundance. We demonstrated for the first time that only one pollinator visitation during the male phase can strongly decrease autonomous selfing by pollen removal. [ABSTRACT FROM AUTHOR]

Abstract: Explosive pollen release is a mechanism used by some angiosperms that serves to attach pollen to a pollinator's body. It is usually adopted by species with zygomorphic tubular flowers and pollinated by birds and bees. The tree genus Meliosma (Sabiaceae, Proteales) has unique disc‐like flowers that are externally actinomorphic, but internally zygomorphic, and release pollen explosively. To elucidate the adaptive significance of explosive pollen release, we observed flowering behaviour, the breeding system and pollinator visits to flowers of the Japanese species Meliosma tenuis in a temperate forest. Flowers bloomed in June and were nectariferous and protandrous. Explosive pollen release was triggered by slight tactile stimuli to anther filaments or staminodes in male‐stage flowers. Because pollen cannot come into contact with the pistils enclosed by staminodes, M. tenuis is functionally protandrous. Artificial pollination treatments revealed that M. tenuis is allogamous. The dominant flower visitors were nectar‐seeking drones of the bumblebee species Bombus ardens (Apidae). The drones’ behaviour, pollen attachment on their bodies and fruit set of visit‐restricted flowers suggest that they are the only agent triggering the explosive pollen release mechanism, and are the main pollinator of M. tenuis. The finding that bumblebee workers rarely visit these flowers suggests that the explosive pollen release has another function, namely to discourage pollen‐harvesting bumblebee workers. [ABSTRACT FROM AUTHOR]

Premise of Study: In a seminal body of theory, Lloyd showed that the fitness consequences of selfing will depend on its timing in anthesis. Selfing that occurs after opportunities for outcrossing or pollen dispersal can provide reproductive assurance when pollinators are limited and is expected to incur little cost, even when inbreeding depression is high. As a result, delayed selfing is often interpreted as a “best‐of‐both‐worlds” mating system that combines the advantages of selfing and outcrossing. Methods: We surveyed 65 empirical studies of delayed selfing, recording floral mechanisms and examining information on inbreeding depression, autofertility, and other parameters to test the support for delayed selfing as a best‐of‐both‐worlds strategy. Key Results: Phylogenetic distribution of the diverse floral mechanisms suggests that some basic floral structures may predispose plant taxa to evolve delayed selfing. Delayed selfing appears to serve as a best‐of‐both‐worlds strategy in some but not all species. While the capacity for autonomous selfing is often high, it is lower, in some cases, than in related species with earlier modes of selfing. In other delayed‐selfers, low inbreeding depression and reduced investment in corollas and pollen suggest limited benefits from outcrossing. Conclusions: Despite a growing literature on the subject, experimental evidence for delayed selfing is limited and major gaps in knowledge remain, particularly with respect to the stability of delayed selfing and the conditions that may favor transitions between delayed and earlier selfing. Finally, we suggest a potential role of delayed selfing in facilitating transitions from self‐incompatibility to selfing. [ABSTRACT FROM AUTHOR]

Nectar secretion was noted both in the male and female floral phases of the protandrous flowers of Campanula patula (Campanulaceae). Female-biased sugar accumulation was evidenced and plasticity in the duration of sexual phases observed. Flowers in the male phase produced twofold less nectar with lower sugar concentrations compared to female-phase flowers. The sugar mass content averaged 0.6 mg ±0.45 SD per flower in the male phase and 1.4 ±0.5 SD per flower in the female phase. The pollen mass averaged 0.16 mg ±0.10 SD per flower. An understanding of the evolution of functional relationships between floral sexes requires consideration of the compensation of the reproductive costs, including the plastic response to interdependent factors, i.e., photosynthesis and growth, the effect of pollinators, pollen robbers, and external environmental forces. [ABSTRACT FROM AUTHOR]

•Variation in flowering phenology is common in natural populations, and is expected to be, together with inter-mate distance, an important driver of effective pollen dispersal. In populations composed of plants with temporally separated sexual phases (i.e. dichogamous or heterodichogamous populations), pollen-mediated gene flow is assumed to reflect phenological overlap between complementary sexual phases. In this study, we conducted paternity analyses to test this hypothesis in the temporally dimorphic tree Acer opalus. •We performed spatially explicit analyses based on categorical and fractional paternity assignment, and included tree size, pair-wise genetic relatedness and morph type as additional predictors. Because differences between morphs in flowering phenology may also influence pollination distances, we modelled separate pollen dispersal kernels for the two morphs. •Extended phenological overlap between male and female phases (mainly associated with inter-morph crosses) resulted in higher siring success after accounting for the effects of genetic relatedness, morph type and tree size, while reduced phenological overlap (mainly associated with intra-morph crosses) resulted in longer pollination distances achieved. Siring success also increased in larger trees. •Mating patterns could not be predicted by phenology alone. However, as heterogeneity in flowering phenology was the single morph-specific predictor of siring success, it is expected to be key in maintaining the temporal dimorphism in A. opalus, by promoting not only a prevalent pattern of inter-morph mating, but also long-distance pollination resulting from intra-morph mating events. [ABSTRACT FROM AUTHOR]

Clerodendrum indicum (Lamiaceae) is a medicinally important shrub. We have studied the details of its pollination ecology which was hitherto unknown. The work was done during three consecutive years 2012-2014, based on 118 plants occurring in three widely separated wild populations in West Bengal, India, together with 25 individuals grown in an experimental plot. Details of flower structure and dynamics of floral events, pollen production and pollen dispersal, visitors and pollinators, floral attractants and floral rewards and pollen transfer mechanism have been worked out by standard methodologies with a 10x high resolution hand lens (IRL), a Leica WILD M3B Stereo-binocular microscope (Switzerland) and a Leica DMLB compound bright field light microscope (Germany). The tubular flower of four-day longevity attracts its visitors by visual cues. Flowers are visited regularly by ten species of insects. On the basis of the visitor behaviour, these can be classified into three distinct categories, viz., visitors belonging to Category-I act on cushion and trichome nectaries of calyx and corolla respectively, those of Category-II act on the dehisced anthers and trichome nectaries of corolla while those of Category-III act on dehisced anthers as well as receptive stigma. Majority of the visitors belong to either Category-I or Category-II. They visit only the 2nd day flowers and never visit a 3rd day flower when the stigma assumes receptivity. Therefore, they are not regarded as pollinators but, act as pollen and/or nectar robbers. Those are discriminated by offering secretions from extra-nuptial nectaries of the flower. Visitor species of Category-III, represented by a species of Trigona, constitute the legitimate pollinator of the plant and thereby, making the plant monophilic. Pollen presentation from the bisexual, dichogamous and protandrous flower takes place on the 2nd day, while the stigma assumes its receptivity on the 3rd day of flower opening. Pollen transfer to the body of the pollinator by a 2nd day flower in its male phase is achieved by offering edible pollen grains. On the other hand, a 3rd day flower at its female phase is devoid of the reward (pollen grain). The yellow shiny receptive stigma of such a flower strikingly mimics the freshly dehisced anthers and the pollinators being lured by such a stigma inadvertently transfer pollen onto it. C. indicum is so far the only known species of flowering plants where deceit pollination occurs by anther-mimicking stigma in a bisexual flower. [ABSTRACT FROM AUTHOR]