The role of genes influencing the corolla in pollination of Antirrhinum majus

Studies of pollination ecology have been hindered by an absence of biochemical information about the basis of polymorphism. Using model plants and mutant lines described by molecular genetics may circumvent this difficulty. Mutation of genes controlling petal colour and petal epidermal cell shape in Antirrhinum majus was previously shown to influence fruit set. White flowers set less fruit than magenta flowers and mutants with flat petal epidermal cells set less fruit than flowers with conical cells. Here we analyse the causal pathway underlying this phenomenon through a study of floral characteristics and bee behaviour. Results indicate that bees recognized plants with magenta conical‐celled flowers at a distance and did not approach white flowers or magenta flat‐celled flowers so frequently. Petal cell shape interacted with colour in determining whether an approaching bee landed on a flower within a plot and whether a bee landing on a flower would probe it. The intrafloral temperature of flowers with conical petal cells was shown to increase with solar irradiance, unlike the intrafloral temperature of flowers with flat petal cells. The difference in fruit set may reflect pollinator discrimination between genotypes as a consequence of the effect of intrafloral temperature on nectar quality and quantity.     

Why do so many petals have conical epidermal cells?

Background

The conical epidermal cells found on the petals of most Angiosperm species are so widespread that they have been used as markers of petal identity, but their function has only been analysed in recent years. This review brings together diverse data on the role of these cells in pollination biology.

Scope

The published effects of conical cells on petal colour, petal reflexing, scent production, petal wettability and pollinator grip on the flower surface are considered. Of these factors, pollinator grip has been shown to be of most significance in the well-studied Antirrhinum majus/bumble-bee system. Published data on the relationship between epidermal cell morphology and floral temperature were limited, so an analysis of the effects of cell shape on floral temperature in Antirrhinum is presented here. Statistically significant warming by conical cells was not detected, although insignificant trends towards faster warming at dawn were found, and it was also found that flat-celled flowers could be warmer on warm days. The warming observed is less significant than that achieved by varying pigment content. However, the possibility that the effect of conical cells on temperature might be biologically significant in certain specific instances such as marginal habitats or weather conditions cannot be ruled out.

Conclusions

Conical epidermal cells can influence a diverse set of petal properties. The fitness benefits they provide to plants are likely to vary with pollinator and habitat, and models are now required to understand how these different factors interact.     

Evolution of petal epidermal micromorphology in Leguminosae and its use as a marker of petal identity

Background and Aims

The legume flower is highly variable in symmetry and differentiation of petal types. Most papilionoid flowers are zygomorphic with three types of petals: one dorsal, two lateral and two ventral petals. Mimosoids have radial flowers with reduced petals while caesalpinioids display a range from strongly zygomorphic to nearly radial symmetry. The aims are to characterize the petal micromorphology relative to flower morphology and evolution within the family and assess its use as a marker of petal identity (whether dorsal, lateral or ventral) as determined by the expression of developmental genes.

Methods

Petals were analysed using the scanning electron microscope and light microscope. A total of 175 species were studied representing 26 tribes and 89 genera in all three subfamilies of the Leguminosae.

Key Results

The papilionoids have the highest degree of variation of epidermal types along the dorsiventral axis within the flower. In Loteae and genistoids, in particular, it is common for each petal type to have a different major epidermal micromorphology. Papillose conical cells are mainly found on dorsal and lateral petals. Tabular rugose cells are mainly found on lateral petals and tabular flat cells are found only in ventral petals. Caesalpinioids lack strong micromorphological variation along this axis and usually have only a single major epidermal type within a flower, although the type maybe either tabular rugose cells, papillose conical cells or papillose knobby rugose cells, depending on the species.

Conclusions

Strong micromorphological variation between different petals in the flower is exclusive to the subfamily Papilionoideae. Both major and minor epidermal types can be used as micromorphological markers of petal identity, at least in papilionoids, and they are important characters of flower evolution in the whole family. The molecular developmental pathway between specific epidermal micromorphology and the expression of petal identity genes has yet to be established.Key words: Epidermis, Fabaceae, Papilionoideae, Caesalpinioideae, Mimosoideae, petal surface, scanning electron microscopy, papillose conical cells, tabular rugose cells, tabular flat cells, organ identity     

Determining the contribution of epidermal cell shape to petal wettability using isogenic Antirrhinum lines

The petal epidermis acts not only as a barrier to the outside world but also as a point of interaction between the flower and potential pollinators. The presence of conical petal epidermal cells has previously been shown to influence the attractiveness of the flower to pollinating insects. Using Antirrhinum isogenic lines differing only in the presence of a single epidermal structure, conical cells, we were able to investigate how the structure of the epidermis influences petal wettability by measuring the surface contact angle of water drops. Conical cells have a significant impact on how water is retained on the flower surface, which may have indirect consequences for pollinator behaviour. We discuss how the petal epidermis is a highly multifunctional one and how a battery of methods, including the use of isogenic lines, is required to untangle the impacts of specific epidermal properties in an ecological context.     

Gloss,Colour and Grip: Multifunctional Epidermal Cell Shapes in Bee- and Bird-Pollinated Flowers

Flowers bear the function of filters supporting the attraction of pollinators as well as the deterrence of floral antagonists. The effect of epidermal cell shape on the visual display and tactile properties of flowers has been evaluated only recently. In this study we quantitatively measured epidermal cell shape, gloss and spectral reflectance of flowers pollinated by either bees or birds testing three hypotheses: The first two hypotheses imply that bee-pollinated flowers might benefit from rough surfaces on visually-active parts produced by conical epidermal cells, as they may enhance the colour signal of flowers as well as the grip on flowers for bees. In contrast, bird-pollinated flowers might benefit from flat surfaces produced by flat epidermal cells, by avoiding frequent visitation from non-pollinating bees due to a reduced colour signal, as birds do not rely on specific colour parameters while foraging. Moreover, flat petal surfaces in bird-pollinated flowers may hamper grip for bees that do not touch anthers and stigmas while consuming nectar and thus, are considered as nectar thieves. Beside this, the third hypothesis implies that those flower parts which are vulnerable to nectar robbing of bee- as well as bird-pollinated flowers benefit from flat epidermal cells, hampering grip for nectar robbing bees. Our comparative data show in fact that conical epidermal cells are restricted to visually-active parts of bee-pollinated flowers, whereas robbing-sensitive parts of bee-pollinated as well as the entire floral surface of bird-pollinated flowers possess on average flat epidermal cells. However, direct correlations between epidermal cell shape and colour parameters have not been found. Our results together with published experimental studies show that epidermal cell shape as a largely neglected flower trait might act as an important feature in pollinator attraction and avoidance of antagonists, and thus may contribute to the partitioning of flower-visitors.     

Sexual dimorphism in nuclear DNA content and floral morphology in populations of Silene latifolia (Caryophyllaceae)

The evolution of flower size has become a major focus of plant population biology. In order to gain insight into the causal basis for flower-size variation, we have explored the relationship between nuclear DNA content, flower size, and cell size within and among populations of the dioecious plant Silene latifolia. We found significant variation among populations for both DNA content and flower size, with a consistent sexual dimorphism within all populations (males have a bigger genome, but smaller flowers). The overall correlation between DNA content and flower size was negative, especially within males. The cell dimensions of calyx and petal cells were not significantly different between the sexes, indicating that females have bigger flowers because they contain more cells. These findings are discussed in the context of nucleotype theory, which predicts a slower growth rate (division rate) for cells with greater DNA content. This leads to the suggestion that males have smaller flowers because of the relatively slow rate of cell division due to their larger genome. It would be of great interest to know whether associated effects on flower size of changes in genome size of the type investigated in the present study can be generalized to other species.     

Petal micromorphology and its relationship to pollination

• The characteristics of petal epidermal conical cells affect the quality of the signals perceived by various pollinators. This study aimed to identify variations in micromorphological characteristics of flower petals and their relationship to melittophily, ornithophily and chiropterophily pollination systems.
• The petals of 11 species were analysed using scanning electron microscopy and optical microscopy and the micromorphological traits were described, measured and compared using Tukey's test, PCA and cluster analysis.
• Unlike chiropterophily, all melittophilous and some ornithophilous species possessed adaxial epidermal conical cells. Cluster grouping separated chiropterophilous flowers from melittophilous and ornithophilous. PCA analysis showed that the two morphometric profile of conical cells was the attribute that most strongly influenced the grouping of species. When considering the data set of the three pollination systems, melittophilous and ornithophilous plants were more similar to each other than they were to chriopterophilous species. The distance between conical cell apices is an important parameter in interactions with pollinators.
• This study facilitated recognition of smoothing pollinator resource access through petal micromorphological characteristics. Further research regarding the biometry of micromorphological traits related to pollination is required.

     

Surprising absence of association between flower surface microstructure and pollination system

• The epidermal cells of flowers come in different shapes and have different functions, but how they evolved remains largely unknown. Floral micro‐texture can provide tactile cues to insects, and increases in surface roughness by means of conical (papillose) epidermal cells may facilitate flower handling by landing insect pollinators. Whether flower microstructure correlates with pollination system remains unknown.
• Here, we investigate the floral epidermal microstructure in 29 (congeneric) species pairs with contrasting pollination system. We test whether flowers pollinated by bees and/or flies feature more structured, rougher surfaces than flowers pollinated by non‐landing moths or birds and flowers that self‐pollinate.
• In contrast with earlier studies, we find no correlation between epidermal microstructure and pollination system. The shape, cell height and roughness of floral epidermal cells varies among species, but is not correlated with pollinators at large. Intriguingly, however, we find that the upper (adaxial) flower surface that surrounds the reproductive organs and often constitutes the floral display is markedly more structured than the lower (abaxial) surface.
• We thus conclude that conical epidermal cells probably play a role in plant reproduction other than providing grip or tactile cues, such as increasing hydrophobicity or enhancing the visual signal.

     

Pollination and reproductive success of two colour variants of a deceptive orchid, Dactylorhiza maculata (Orchidaceae)

Polymorphism in petal colour is common in deceptively pollinated plant species. Most of the deceptively pollinated orchids are food frauds, and in most of them, the deception is not mimetic. These plants have conspicuously coloured flowers which they use as the main attractant of naive pollinators. In a field experiment, we studied the response of bumblebees and other types of flower visitors to colour differences between experimentally paired plants of Dactylorhiza maculata , a nectarless food-deceptive species. In addition, pollen removal, an estimate of male fitness, and fruit production, an estimate of female fitness, were measured in the two colour variants. We found a trend of bumblebee preference for the dark-coloured flowers, but other flower visitors (as a group) showed no preference for any colour variant. No difference was found in the reproductive success between the two colour variants of D. maculata. The lack of a difference in reproductive success between plants with pale and dark inflorescences, despite the observed trend of bumblebee preference for dark inflorescences, suggests that there is some balancing factor in the pollination of the pale inflorescences. An excess of visits by some nocturnal species (or a group of species) which favours the pale colour of D. maculata inflorescences or an excess of visits during day time by some flower visitors other than bumblebees preferring the pale inflorescences over dark ones may form such a balancing factor.     

Hummingbird color preference within a natural hybrid population of Mimulus aurantiacus (Phrymaceae)

Hummingbird flowers are typically red in color but the reasons for this are not well understood. Relatively few studies have examined hummingbird flower color preferences under natural conditions in which flower color varies within a species. We recorded hummingbird visitation rates to flowers that vary in color from yellow to red in a natural hybrid population between red‐ and yellow‐flowered Mimulus aurantiacus subspecies. We also examined whether there were any correlations between color and flower size or nectar content. Finally, we reviewed the literature on hummingbird color choice tests using feeders and flowers. There were no correlations in this population between flower color and flower size, nectar volume, or sugar concentration. Nevertheless, hummingbirds undervisited the two most yellow color classes, overvisited orange flowers, and visited the two most red color classes in proportion to their frequency in the population. While Hummingbirds preferred flowers expressing red pigments to those that did not, the flowers with the most red hue were not the most attractive, as has been observed in similar studies with other species of Mimulus. While feeder studies generally fail to show hummingbird preference for red, all studies using flowers, including those that control all floral traits other than color, find consistent preference for red. Experiments are suggested that might help disentangle hypotheses for why hummingbirds exhibit this preference.     

福建山樱花天然居群表型变异研究

以闽、赣、粤三省天然分布的福建山樱花(Cerasus campanulata Maxim.)为研究对象,调查了11个居群226个单株的17个表型性状指标,运用变异系数和单因子方差分析研究了居群间和居群内的表型变异;应用相关分析揭示了表型性状间及其与地理、气候因子间的相关性以及表型变异的地理格局;并且运用聚类分析进行了居群分类.结果表明,福建山樱花天然居群内的变异远大于居群间的变异,居群分化较小;花色、花量与经度、纬度间显著或极显著相关,花瓣宽与纬度、海拔显著或极显著相关,花色、花量与年降雨量极显著相关,花量、花瓣宽、开花习性与年日照时数显著相关,花瓣宽与年均温、无霜期显著或极显著相关,存在较明显的地理变异趋势.而居群间马氏距离聚类分析结果与参试居群分布地域性呈现高度一致,二者之间相关显著.     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica北大核心CSCD

Aims: Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development. Methods: We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods. Important findings: Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.     

A theoretical approach to the relationship between wettability and surface microstructures of epidermal cells and structured cuticles of flower petals

Background and Aims The epidermal surface of a flower petal is composed of convex cells covered with a structured cuticle, and the roughness of the surface is related to the wettability of the petal. If the surface remains wet for an excessive amount of time the attractiveness of the petal to floral visitors may be impaired, and adhesion of pathogens may be promoted. However, it remains unclear how the epidermal cells and structured cuticle contribute to surface wettability of a petal.Methods By considering the additive effects of the epidermal cells and structured cuticle on petal wettability, a thermodynamic model was developed to predict the wetting mode and contact angle of a water droplet at a minimum free energy. Quantitative relationships between petal wettability and the geometries of the epidermal cells and the structured cuticle were then estimated. Measurements of contact angles and anatomical traits of petals were made on seven herbaceous species commonly found in alpine habitats in eastern Nepal, and the measured wettability values were compared with those predicted by the model using the measured geometries of the epidermal cells and structured cuticles.Key Results The model indicated that surface wettability depends on the height and interval between cuticular steps, and on a height-to-width ratio for epidermal cells if a thick hydrophobic cuticle layer covers the surface. For a petal epidermis consisting of lenticular cells, a repellent surface results when the cuticular step height is greater than 0·85 µm and the height-to-width ratio of the epidermal cells is greater than 0·3. For an epidermis consisting of papillate cells, a height-to-width ratio of greater than 1·1 produces a repellent surface. In contrast, if the surface is covered with a thin cuticle layer, the petal is highly wettable (hydrophilic) irrespective of the roughness of the surface. These predictions were supported by the measurements of petal wettability made on flowers of alpine species.Conclusions The results indicate that surface roughness caused by epidermal cells and a structured cuticle produces a wide range of petal wettability, and that this can be successfully modelled using a thermodynamic approach.     

Factors affecting floral herbivory in a limestone grassland

The amount of herbivore damage to the petals of 41 species of herbaceous plant was surveyed from April to September in a limestone grassland in central England. Damage was recorded as the percentage of the petal area removed. Most damage was caused by invertebrates, particularly slugs. The amount of invertebrate damage differed significantly between plant species and with time of year. The mean damage across all species was only 2 %, ranging from an average of 0 % in Galium sterneri to 8 % in Primula vulgaris. In most species, less than a quarter of flowers received any damage, so those that were damaged were often severely affected. Species flowering early or late in the season received more damage, possibly because of greater slug activity. Hypotheses to explain the inter-specific variation in the amount of herbivory were examined by testing for correlations with a range of plant variables. No correlations with flower-stem length, flower-stem thickness or the longevity of flowers were apparent. The amount of petal damage correlated strongly with flower size and petal thickness. This appeared to result from the prevalence of large-flowered species early and late in the season rather than from a preference for flower size and petal thickness per se. The evolutionary significance of floral herbivory is discussed.     

Stigma development and receptivity in almond (Prunus dulcis)

BACKGROUND AND AIMS: Fertilization is essential in almond production, and pollination can be limiting in production areas. This study investigated stigma receptivity under defined developmental stages to clarify the relationship between stigma morphology, pollen germination, tube growth and fruit set. METHODS: Light and scanning electron microscopy were employed to examine stigma development at seven stages of flower development ranging from buds that were swollen to flowers in which petals were abscising. Flowers at different stages were hand pollinated and pollen germination and tube growth assessed. Artificial pollinations in the field were conducted to determine the effect of flower age on fruit set. KEY RESULTS: Later stages of flower development exhibited greater stigma receptivity, i.e. higher percentages of pollen germination and more extensive tube growth occurred in older (those opened to the flat petal stage or exhibiting petal fall) than younger flowers. Enhanced stigma receptivity was associated with elongation of stigmatic papillae and increased amounts of stigmatic exudate that inundated papillae at later developmental stages. Field pollinations indicated that the stigma was still receptive and nut set was maintained in older flowers. CONCLUSIONS: Stigma receptivity in almond does not become optimal until flowers are past the fully open stage. The stigma is still receptive and fruit set is maintained in flowers even at the stage when petals are abscising. Strategies to enhance pollination and crop yield, including the timing and placement of honey bees, should consider the effectiveness of developmentally advanced flowers.     

Where have all the blue flowers gone: pollinator responses and selection on flower colour in New Zealand Wahlenbergia albomarginata

Although pollinators are thought to select on flower colour, few studies have experimentally decoupled effects of colour from correlated traits on pollinator visitation and pollen transfer. We combined selection analysis and phenotypic manipulations to measure the effect of petal colour on visitation and pollen export at two spatial scales in Wahlenbergia albomarginata. This species is representative of many New Zealand alpine herbs that have secondarily evolved white or pale flowers. The major pollinators, solitary bees, exerted phenotypic selection on flower size but not colour, quantified by bee vision. When presented with manipulated flowers, bees visited flowers painted blue to resemble a congener over white flowers in large, but not small, experimental arrays. Pollen export was higher for blue flowers in large arrays. Pollinator preference does not explain the pale colouration of W. albomarginata, as commonly hypothesized. Absence of bright blue could be driven instead by indirect selection of correlated characters.     

SEX ALLOCATION IN THE MONOECIOUS HERB BEGONIA SEMIOVATA

Sex-allocation models predict that the evolution of self-fertilization should result in a reduced allocation to male function and pollinator attraction in plants. The evolution of sex allocation may be constrained by both functional and genetic factors, however. We studied sex allocation and genetic variation for floral sex ratio and other reproductive traits in a Costa Rica population of the monoecious, highly selfing annual Begonia semiovata. Data on biomass of floral structures, flower sex ratios, and fruit set in the source population were used to calculate the average proportion of reproductive allocation invested in male function. Genetic variation and genetic correlations for floral sex ratio and for floral traits related to male and female function were estimated from the greenhouse-grown progeny of field-collected maternal families. The proportion of reproductive biomass invested in male function was low (0.34 at flowering, and 0.07 for total reproductive allocation). Significant among-family variation was detected in the size (mass) of individual male and female flowers, in the proportion of male flowers produced, and in the proportion of total flower mass invested in male flowers. Significant among-family variation was also found in flower number per inflorescence, petal length of male and female flowers, and petal number of female flowers. Except for female petal length, we found no difference in the mean value of these characters between selfed and outcrossed progeny, indicating that, with the possible exception of female petal length, the among-family variation detected was not the result of variation among families in the level of inbreeding. Significant positive phenotypic and broad-sense genetic correlations were detected between the mass of individual male and female flowers, between male and female petal length, and between number of male and number of female flowers per inflorescence. The ratio of stamen-to-pistil mass (0.33) was low compared to published data for autogamous species with hermaphroditic flowers, suggesting that highly efficient selfing mechanisms may evolve in monoecious species. Our results indicate that the study population harbors substantial genetic variation for reproductive characters. The positive genetic correlation between investment in male and female flowers may reflect selection for maximum pollination efficiency, because in this self-pollinating species, each female flower requires a neighboring male flower to provide pollen.     

Temporal,but not spatial,changes in expression patterns of petal identity genes are associated with loss of papillate conical cells and the shift to bird pollination in Macaronesian Lotus (Leguminosae)

• In the generally bee‐pollinated genus Lotus a group of four species have evolved bird‐pollinated flowers. The floral changes in these species include altered petal orientation, shape and texture. In Lotus these characters are associated with dorsiventral petal identity, suggesting that shifts in the expression of dorsal identity genes may be involved in the evolution of bird pollination. Of particular interest is Lotus japonicus CYCLOIDEA 2 (LjCYC2), known to determine the presence of papillate conical cells on the dorsal petal in L. japonicus. Bird‐pollinated species are unusual in not having papillate conical cells on the dorsal petal.
• Using RT‐PCR at various stages of flower development, we determined the timing of expression in all petal types for the three putative petal identity genes (CYC‐like genes) in different species with contrasting floral morphology and pollination syndromes.
• In bird‐pollinated species the dorsal identity gene, LjCYC2, is not expressed at the floral stage when papillate conical cells are normally differentiating in bee‐pollinated species. In contrast, in bee‐pollinated species, LjCYC2 is expressed during conical cell development.
• Changes in the timing of expression of the above two genes are associated with modifications in petal growth and lateralisation of the dorsal and ventral petals in the bird‐pollinated species. This study indicates that changes in the timing, rather than spatial distribution, of expression likely contribute to the modifications of petal micromorphology and petal size during the transition from bee to bird pollination in Macaronesian Lotus species.

     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica

Aims Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development.Methods We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods.Important findings Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.