Floral Whorls Research Articles

A single dominant GLOBOSA allele accounts for repeated origins of hose-in-hose flowers in Sinningia (Gesneriaceae).

Plants bearing double flowers have long been cultivated as ornamental plants. Hose-in-hose flowers, bearing 2-whorled corolla tubes in whorls 1 and 2, are uncommon but recur in Sinningia (Gesnerioideae, Gesneriaceae). In this study, we selected 15 hose-in-hose cultivars as materials to explore the underlying molecular and genetic mechanisms of this floral architecture. We found that they originated from different hybridization events within the Dircaea clade. Three B-class MADS-box genes were globally expressed in all floral whorls, but only GLOBOSA1 (GLO1) has accumulated a dominant mutation, i.e., the insertion of a hAT-like miniature inverted-repeat transposable element (MITE) into its promoter, that co-segregated with the hose-in-hose phenotype. In addition, all 15 hose-in-hose cultivars contained the same dominant GLO1 allele. Transient gene expression assays confirmed the role of this MITE insertion in up-regulating the promoter activity of GLO1 by providing several cis-regulatory elements. Genetic transformation in heterologous Chirita pumila (Didymocarpoideae, Gesneriaceae) verified that this dominant GLO1 allele is sufficient to confer the hose-in-hose phenotype. We further demonstrated that both the GLO1 allele and the hAT-like MITE descended from wild S. cardinalis with single flowers. This study highlights the significance of wide hybridization in frequent gains of the dominant GLO1 allele and thereafter repeated occurrence of hose-in-hose flowers in Sinningia.

Functional retrogression of LOFSEPs in specifying floral organs in barley

AbstractThe barley genome encodes a complete set of MADS-box proteins sharing homology with components of the ABCDE model, which explains the molecular basis of floral organ identity in angiosperm flowers. Although the E-class members are universally expressed across floral whorls and crucial for flower development in Arabidopsis and rice, the functional role of the barley E-class LOFSEP subfamily (comprising MADS1, MADS5, and MADS34) remains elusive, particularly during spikelet formation. Here, we characterize the single, double and triple lofsep mutants in barley in an attempt to overcome the anticipated genetic redundancy. Surprisingly, loss of function of all LOFSEP members only disturbs lemma development, either converting this hull organ into a leaf-like structure or reducing its size. The inner organs, including lodicules, anthers and pistil remain unaffected. A systematic interrogation of how ABCDE class genes are affected in all whorls of the mutants was undertaken. Generally, in the lemma and palea of the lofsep mutants, A- and E-class genes are hyperactivated, B- and C- classes are slightly repressed, and D-class genes show unchanged expression in these inner organs. Intriguingly, loss of function of MADS6, an AGL6 member closely related to the E-class genes, leads to most organs being transformed into lemma-like organs with new spikelets generated from the center of the flower. Contrasting with rice, these findings suggest barley LOFSEPs may have regressed in determining floral organ identity, and this could be partially compensated by HvMADS6.

A new endemic Begonia species (sect. Knesebeckia, Begoniaceae) from the south-western montane forest remnants of Ecuador

Begonia jocotocoi is a new species described from the Buenaventura Reserve in El Oro Province, south-west Ecuador. The new species morphologically resembles Begonia serotina, but differs by its minutely bullate leaf lamina (vs. smooth), the dense red long trichomes that cover the petioles and the lower surface of the leaf lamina, the latter of which distinctly become purple at maturity (vs. usually glabrous or occasionally with an indument of minute glandular white hairs and pale green below), presence of a pair of bracteoles directly beneath the pistillate flowers (vs. bracteoles absent), and the pedicels and also sometimes the abaxial surfaces of most floral whorls having a sparse cover of glandular hairs (vs. glabrous to puberulous). Photos of the new species and a distribution map are provided. Relationships with other species are discussed and the species’ preliminary conservation status is assigned as critically endangered (CR).

Alternative splicing variants of IiSEP3 in Isatis indigotica are involved in floral transition and flower development

The SEPALLATA3 genes regulate several aspects of plant development. This study identified four distinct splicing isoforms of the SEPALLATA3 gene in Isatis indigotica (I. indigotica). IiSEP3-1 and IiSEP3-2 have eight exons and were named as IiSEP3-2/1. However, IiSEP3-3 and IiSEP3-4 with the missing sixth exon were labeled IiSEP3ΔK3. Furthermore, the IiSEP3-1 and IiSEP3-4 amino acids sequences lack the V90. IiSEP3 splicing variants were primarily expressed in floral organs, with petals showing the highest expression. Ectopic expression of IiSEP3-2 or IiSEP3-3 may cause early flowering and reduce the number of sepals, petals, and stamens. The ectopic expression of IiSEP3-2 resulted in cauline leaves and sepals converting to carpelloid structures. In contrast, the four floral whorls prematurely wilted, and the entire flower displayed an abortive state when IiSEP3-3 was expressed ectopically. Silencing the IiSEP3 gene of I. indigotica employing VIGS (tobacco rattle virus-mediated virus-induced gene silencing) technology using the TRV-IiSEP3-2/1 vector delayed flowering time and reduced the number of petals and stamens. Plants silenced with TRV-IiSEP3ΔK3 also exhibited similar phenotypes, including fewer sepals. The transcriptome analysis of silenced plants (TRV-IiSEP3-2/1 treatment group) indicated significant alterations in 1861 genes, with 1035 upregulated and 826 downregulated. TRV-IiSEP3ΔK3 treatment altered the expression of 2063 genes in plants, with 1289 genes upregulated and 774 genes transcription inhibited. Y2H and BIFC experiments revealed that IiSEP3-2 and IiSEP3-3 had distinct interacting proteins. Thus, we can conclude that IiSEP3-2 and IiSEP3-3 interact with different proteins, affecting floral transition and organ development in I. indigotica.

Transcriptome wide analysis of MADS box genes in Crocus sativus and interplay of CstMADS19-CstMADS26 in orchestrating apocarotenoid biosynthesis

Flowers of Crocus sativus L. are immensely important not only for arrangement of floral whorls but more because each floral organ is dominated by a different class of specialized compounds. Dried stigmas of C. sativus flowers form commercial saffron, and are known to accumulate unique apocarotenoids like crocin, picrocrocin and safranal. Inspite of being a high value crop, the molecular mechanism regulating flower development in Crocus remains largely unknown. Moreover, it would be very interesting to explore any co-regulatory mechanism which controls floral architecture and secondary metabolic pathways which exist in specific floral organs. Here we report transcriptome wide identification of MADS box genes in Crocus. A total of 39 full length MADS box genes were identified among which three belonged to type I and 36 to type II class. Phylogeny classified them into 11 sub-clusters. Expression pattern revealed some stigma up-regulated genes among which CstMADS19 encoding an AGAMOUS gene showed high expression. Transient over-expression of CstMADS19 in stigmas of Crocus resulted in increased crocin by enhancing expression of pathway genes. Yeast one hybrid assay demonstrated that CstMADS19 binds to promoters of phytoene synthase and carotenoid cleavage dioxygenase 2 genes. Yeast two hybrid and BiFC assays confirmed interaction of CstMADS19 with CstMADS26 which codes for a SEPALATA gene. Co-overexpression of CstMADS19 and CstMADS26 in Crocus stigmas enhanced crocin content more than was observed when genes were expressed individually. Collectively, these findings indicate that CstMADS19 functions as a positive regulator of stigma based apocarotenoid biosynthesis in Crocus.

Integrated morphological analysis of floral nectaries and androecia in the tribe Phaseoleae (Leguminosae, Papilionoideae)

Flowers of Leguminosae, the third largest angiosperm family, display outstanding diversity and are adapted to different modes of pollination. However, floral nectar is their most common and important reward. The morphology and position of the specialized floral nectaries (FNs) have been described only in the minority of legumes to date, so the investigation of these structures requires a further progress. The exact origin of these nectaries in legumes has been a matter of debate for more than a century. It was hypothesized that FNs are either of staminal origin or have no homology with any floral organs. This paper is devoted to the morphological study, using scanning electron microscopy (SEM), of the floral nectaries in seven taxa of the tribe Phaseoleae, with a focus on their localization, timing of their emergence, symmetry, along with a discussion of their possible identity. Some features of the androecium morphology potentially related to the interaction with pollinators were also studied. Although FNs have an annular habit in all studied species, they possess some features of monosymmetry, such as bilabiate shape or uneven distribution of secretory stomata. These FNs emerge late in ontogeny when all other floral parts are already differentiated and may be either free from other floral parts or adnate to the hypanthium. It is hypothesized that the leguminous FNs are not derived from stamens but represent structures sui generis although their spatial patterning is most probably dependent on some pentamerous floral whorl(s), i.e., a perianth or an androecium.

Floral traits and functional role of whorls in pollinator attraction of Magnolia grandiflora L.

Abstract Species within the primitive genus Magnolia may often produce specialized floral traits and behaviour to grab the attention of potential pollinators from their surroundings. These reproductive traits in plants undergo various selection pressures and frequently bring forth variations to adapt to the new habitat that may result in speciation. We have aimed to understand the floral traits, the functional role of floral parts, and the variable response of visitors in Magnolia grandiflora belonging to an ancient order Magnoliales. Our observations reveal that the floral traits of M. grandiflora resemble those of basal angiosperms, conforming to the primitive existence of the genus Magnolia. The inconsistency in floral form reflected that M. grandiflora has been experiencing various selection pressures from biotic and abiotic factors. Inconsistency in floral equations and diagrams reflect the structural variability in flowers, which can directly impact pollination and reproductive output. SEM images of pollen grains reveal that the pollen grains were monocolpate and boat-shaped in structure. GC-MS analysis showed that VOCs in stigmatic exudation of the flower were largely composed of terpene hydrocarbons such as Perthenine, β-Elemene, β-Caryophyllene, α-Humulene, Bicyclogermacrene, Germacrene A and D, etc. Beyond pollinators attraction, VOCs play a major role in repelling unwanted visitors and in improving the defensive mechanisms in Magnolia. Beetles, bees, and flies were found to be the active pollinators and the behaviour of bees indicates that bees were trying to replace the role of beetles in pollinating M. grandiflora. In summary, floral whorls were diversely functionalized to ensure maximum reproduction in M. grandiflora.

APETALA2-like Floral Homeotic Protein Up-Regulating FaesAP1_2 Gene Involved in Floral Development in Long-Homostyle Common Buckwheat.

In the rosid species Arabidopsis thaliana, the AP2-type AP2 transcription factor (TF) is required for specifying the sepals and petals identities and confers a major A-function to antagonize the C-function in the outer floral whorls. In the asterid species Petunia, the AP2-type ROB TFs are required for perianth and pistil development, as well as repressing the B-function together with TOE-type TF BEN. In Long-homostyle (LH) Fagopyrum esculentum, VIGS-silencing showed that FaesAP2 is mainly involved in controlling filament and style length, but FaesTOE is mainly involved in regulating filament length and pollen grain development. Both FaesAP2 (AP2-type) and FaesTOE (TOE-type) are redundantly involved in style and/or filament length determination instead of perianth development. However, neither FaesAP2 nor FaesTOE could directly repress the B and/or C class genes in common buckwheat. Moreover, the FaesAP1_2 silenced flower showed tepal numbers, and filament length decreased obviously. Interestingly, yeast one-hybrid (Y1H) and dual-luciferase reporter (DR) further suggested that FaesTOE directly up-regulates FaesAP1_2 to be involved in filament length determination in LH common buckwheat. Moreover, the knockdown of FaesTOE expression could result in expression down-regulation of the directly target FaesAP1_2 in the FaesTOE-silenced LH plants. Our findings uncover a stamen development pathway in common buckwheat and offer deeper insight into the functional evolution of AP2 orthologs in the early-diverging core eudicots.

B-class floral homeotic gene MapoAPETALA3 may play an important role in the origin and formation of multi-tepals in Magnolia polytepala

In angiosperms, floral architecture diversity reflects its significance in exploring plant evolution. Magnolia polytepala, an endemic and ancient species in China, possesses a unique multi-tepal trait. Notably, the origin and formation of these multi-tepals are poorly understood. In this study, we investigated the origin and formation of multi-tepals from the inner floral whorl and elucidated the underlying molecular regulatory mechanisms by combining phenotypic analysis, sequencing, and molecular experiments. We found that the multi-tepals exhibited morpho-anatomical characteristics similar to normal tepals but differed from petaloid and normal stamens. The temporal dynamics of a large number of differentially expressed genes (DEGs) involved in multiple signaling (transduction) pathways contributed to multi-tepal primordia initiation during early floral differentiation. In particular, the dynamic expression of MpWOX4, MpCLE41, MpULT1, and MpKN1 might be responsible for floral meristem activation and maintenance, while MpTGA1 and MpEJ2 potentially regulated floral organ initiation. Floral homeotic genes, such as MapoAP3, contributed to subsequent organ identity specialization. We further isolated a nucleus-localized APETALA3 homolog from M. polytepala, terming it the MapoAPETALA3 (MapoAP3) gene, which was expressed in almost all vegetative and reproductive tissues. Ectopically expressing MapoAP3 in Arabidopsis resulted in altered phenotypes of rosette leaves, inflorescences, and florets, particularly generating extra petals instead of undergoing homeotic organ conversion. This discovery revealed an additional function of MapoAP3 in regulating organ initiation in addition to its conserved B-function in floral architecture plasticity. In summary, the multi-tepals of M. polytepala originated from the early tepal primordia initiation event rather than stamen petalody. The formation of the multi-tepal trait was attributed to the coordinated regulation of several vital DEGs, with the MapoAP3 gene playing an important role. These results provide additional insight into the regulation underlying the floral architecture formation in ancient Magnolia species and suggest that manipulating the MapoAP3 gene may hold promising potential for genetic breeding in ornamental plants.

Floral Morphometry and Sexual System Determination in Pink Pepper (Schinus terebinthifolia - Anacardiaceae).

The increasing global importance of pink peppertree (Schinus terebinthifolia, Anacardiaceae) as a high-value commercial crop and its potential for expansion in production demand appropriate management due to uncertainties regarding its sexual system. This study focused on evaluating the morphology of sterile and fertile floral whorls, as well as analyzing the sexual system of pink pepper in two populations in northeastern Brazil. The results revealed no significant differences in the morphological characteristics of the flowers between the studied areas, suggesting that the species possesses notable adaptability to environmental conditions. However, a significant difference in the proportion of staminate individuals was observed in both areas, representing over 88% and 72%, respectively. A correlation was observed between the size of the stamens and the presence of apparently atrophied pistils (r=0.275; df=178; p<0.001), along with the occurrence of fruits in these hermaphroditic plants. In this context, the species should be considered gynodioecious due to the presence of plants with hermaphroditic flowers and plants with pistillate flowers. However, further research is essential to elucidate the role of pollinators, especially bees and wasps, and to better understand the fruiting process in hermaphroditic flowers. These insights have the potential to significantly enhance management aiming for efficient fruit production, promoting its economic and ecological relevance.

A high-resolution gene expression map of the medial and lateral domains of the gynoecium of Arabidopsis.

Angiosperms are characterized by the formation of flowers, and in their inner floral whorl, one or various gynoecia are produced. These female reproductive structures are responsible for fruit and seed production, thus ensuring the reproductive competence of angiosperms. In Arabidopsis (Arabidopsis thaliana), the gynoecium is composed of two fused carpels with different tissues that need to develop and differentiate to form a mature gynoecium and thus the reproductive competence of Arabidopsis. For these reasons, they have become the object of study for floral and fruit development. However, due to the complexity of the gynoecium, specific spatio-temporal tissue expression patterns are still scarce. In this study, we used precise laser-assisted microdissection and high-throughput RNA sequencing to describe the transcriptional profiles of the medial and lateral domain tissues of the Arabidopsis gynoecium. We provide evidence that the method used is reliable and that, in addition to corroborating gene expression patterns of previously reported regulators of these tissues, we found genes whose expression dynamics point to being involved in cytokinin and auxin homeostasis and in cell cycle progression. Furthermore, based on differential gene expression analyses, we functionally characterized several genes and found that they are involved in gynoecium development. This resource is available via the Arabidopsis eFP browser and will serve the community in future studies on developmental and reproductive biology.

Pushing the boundaries of organ identity: Homology of the grass lemma

Pushing the boundaries of organ identity: Homology of the grass lemma

Teucrium fruticans L., a Multi-Scale Study: From Trichomes to Essential Oil.

This work represents the first multi-scale study on Teucrium fruticans L. cultivated at the Ghirardi Botanic Garden (Lombardy, Northern Italy), combining a micromorphological and a phytochemical survey on the plant's aerial parts. Micromorphological investigations, performed by Light Microscopy, Fluorescence Microscopy and Scanning Electron Microscopy, highlighted the presence of five trichomes morphotypes, distinguished by a different distribution pattern: peltates, short-stalked and ball-like medium-stalked capitates, ubiquitous on the whole plant, medium-stalked and long-stalked capitates, exclusive to the floral whorls. Both peltates and medium-stalked capitates were recognized as the main terpene production sites. Phytochemical characterization focused on the essential oils (EOs), obtained by Clevenger-type hydrodistillation in February and April 2022 and characterized by Gas Chromatography-Mass Spectrometry (GC/MS), which resulted mainly formed by sesquiterpene hydrocarbons. The February EO profile was characterized by β-caryophyllene (28.30 %) and germacrene D (19.16 %) as main compounds, while in April β-myrcene was detected at high percentage (13.77 %), in addition to the previous two components (15.72 % and 11.55 %, respectively). Literature data, dealing with the biological activities of the main oil constituents, highlighted an anti-microbial, anti-inflammatory, and anti-tumor potential, due to the high content in sesquiterpenes and, particularly, of β-caryophyllene and germacrene D.

Emended description of the South American genus Elephantomene (Menispermaceae)

Elephantomene is a monospecific genus, distributed in South America. To our knowledge, there are no studies about the pistillate flower in Elephantomene eburnea. This is the first complete taxonomic description involving all floral whorls of staminate and pistillate flowers. Between January 2018 and October 2021, including types housed at 32 national and foreign herbaria. In the Neotropics, the Amazonian is the main center of concentration for the genus. The tripartite gynophores, the internal sepals fused forming a solid column and the stamens inserted in this column were the main characters used to identify the species. Descriptions and illustrations of the species are presented, as well as data concerning geographical distribution and additional comments of the species.

The 1991 review by Coen and Meyerowitz on the war of the whorls and the ABC model of floral organ identity.

The 1991 review paper by Coen and Meyerowitz on the control of floral organ development set out the evidence available at that time, which led to the now famous ABC model of floral organ identity control. The authors summarised the genetic and molecular analyses that had been carried out in a relatively short time by several laboratories, mainly in Arabidopsis thaliana and Antirrhinum majus. The work was a successful example of how systematic genetic and molecular analysis can decipher the mechanism that controls a developmental process in plants. The ABC model is a combinatorial model in which each floral whorl acquires its identity through a unique combination of floral homeotic gene activities. The review also highlights the similarities in the regulation of floral organ identity between evolutionarily distant plant species, emphasising the general relevance of the model and paving the way for comprehensive studies of the evolution of floral diversity.

The TIFY family protein CmJAZ1-like negatively regulates petal size via interaction with the bHLH transcription factor CmBPE2 in Chrysanthemum morifolium.

Petals are the second floral whorl of angiosperms, exhibiting astonishing diversity in their size between and within species. This variation is essential for protecting their inner reproductive organs and attracting pollinators for fertilization. However, currently, the genetic and developmental control of petal size remains unexplored. Chrysanthemum (Chrysanthemum morifolium) belongs to the Asteraceae family, the largest group of angiosperms, and the extraordinary diversity of petal size in chrysanthemums makes it an ideal model for exploring the regulation mechanism of petal size. Here, we reveal that overexpression of a JAZ repressor CmJAZ1-like exhibits decreased petal size compared to that of the wild-type as a result of repressed cell expansion. Through further in-depth exploration, we confirm an interaction pair between CmJAZ1-like and the bHLH transcription factor CmBPE2. The inhibition of CmBPE2 expression negatively regulates petal size by downregulating the expression of genes involved in cell expansion. Furthermore, CmJAZ1-like significantly reduced the activation ability of CmBPE2 on its target gene CmEXPA7 by directly interacting with it, thus participating in the regulation of petal size development in chrysanthemum. Our results will provide insights into the molecular mechanisms of petal size regulation in flowering plants.

Tracing the Evolution of the SEPALLATA Subfamily across Angiosperms Associated with Neo- and Sub-Functionalization for Reproductive and Agronomically Relevant Traits.

SEPALLATA transcription factors (SEP TFs) have been extensively studied in angiosperms as pivotal components of virtually all the MADS-box tetrameric complex master regulators of floral organ identities. However, there are published reports that suggest that some SEP members also regulate earlier reproductive events, such as inflorescence meristem determinacy and inflorescence architecture, with potential for application in breeding programs in crops. The SEP subfamily underwent a quite complex pattern of duplications during the radiation of the angiosperms. Taking advantage of the many whole genomic sequences now available, we present a revised and expanded SEP phylogeny and link it to the known functions of previously characterized genes. This snapshot supports the evidence that the major SEP3 clade is highly specialized for the specification of the three innermost floral whorls, while its sister LOFSEP clade is functionally more versatile and has been recruited for diverse roles, such as the regulation of extra-floral bract formation and inflorescence determinacy and shape. This larger pool of angiosperm SEP genes confirms previous evidence that their evolution was driven by whole-genome duplications rather than small-scale duplication events. Our work may help to identify those SEP lineages that are the best candidates for the improvement of inflorescence traits, even in far distantly related crops.

A short review on identification of ABCDE genes in monocot plants

One of the most important divisions in the plant kingdom is the monocotyledon division of angiosperms. More than 60,000 monocot spp. have been identified, the majority of which are economically important, such as the Poaceae, Orchidaceae, Arecaceae, Liliaceae, and certain other families. The involvement of the ABCDE model of floral organ determination during flower development is a growing area of research in the field of molecular biology due to the diversity in the floral morphology of monocots. The MADS-box gene family is a large molecular transcript family that helps identifies specific proteins involved in floral development. It is classified into several classes based on its function. The review aimed to evaluate the significance of ABCDE genes for floral development and subsequent organ identification, which have been discovered in a range of monocot plants, as well as the functions of these genes in determining the sex of dioecious plants. We sought to summarise the MADSbox gene responsible for flower initiation and floral whorl differentiation reported in economically valuable monocotyledonous plants. Keywords: ABCDE model, Dioecious, Floral organ identity, MADS-box gene,Monocots

Florivory in twoChamaecristaspecies: Are secretory trichomes effective against florivores?

AbstractFlorivory inChamaecristavaries in occurrence, intensity, and the floral structures affected. As flowers are multifunctional units, the type of damage can impact reproductive success in different ways. Oil‐resin‐secreting trichomes, present in the sepals ofChamaecristaspecies, section Absus, are suggested to inhibit florivory. We recorded florivory inChamaecrista catharticaandChamaecrista catharticoidesin order to determine the frequency of damage, floral whorls most damaged, impact on reproduction, and effectiveness of secretory trichomes in inhibiting florivory. The study was conducted in the Parque Estadual do Ibitipoca, Brazil. Twenty individuals of each species were monitored monthly over two bloom periods to record the flowering intensity, rates of florivory, and fruit set and to determine the effectiveness of trichomes in inhibiting florivory. The two species had different flowering patterns, annual forC. catharticaand continuous forC. catharticoides, both more intense during summer. Florivory occurred mainly in the winter and affected floral structures unevenly, resulting in loss of different floral functions. Florivory reduced the fruit set of both species, butC. catharticoideswas considerably more impacted. The diversity of damaged structures inC. catharticoidesresulted in direct (reduced female and male fitness due to loss of ovules and pollen grains) and indirect (loss of floral resources and reduced floral attractiveness) impacts. Damage to the tubular petal could further result in loss of specialized pollination mechanisms mediated by this structure. Secretory trichomes on the abaxial surface of sepals inhibited florivory of buds and herbivory of early‐developing fruits.

Inaccuracy of sexual organ position and spatial variation of styles in monomorphic enantiostylous flowers of Senna rugosa (Fabaceae-Caesalpinioideae)

Differences in the arrangement of floral whorls in enantiostylous species may affect the levels of reciprocity between the sexual organs of floral morphs and the functionality of the enantiostyly. In this study, we aimed to investigate enantiostyly in Senna rugosa, evaluating the variation in the position of sexual organs. Using different spatial measures, we investigated the level of herkogamy and used the inaccuracy index to describe the level of reciprocity between stigmas and anthers of different floral types and within the same floral type. We investigated the proportion of floral types within individuals of the population based on the position of the curved petal and the stigma. Stigmas of left-styled flowers are more likely to capture inter-morph pollen, whereas stigmas of right-styled flowers may receive greater proportions of intra-morph pollen. Horizontal distance was most responsible for the non-overlap of the sexual organs, whereas height was the measure that contributed most to their proximity. Individuals showed a similar proportion of floral types. However, from a morpho-functional perspective, the proportion of flowers differed, with a lower proportion of functionally left-styled flowers. Both floral types have functionally right-, left-, and central-styled flowers. Our study is the first report of a possible division of reproductive functions in pollen uptake between opposite floral types, a mechanism that may have evolved to provide reproductive assurance, and the second report of the presence of functionally central styles within the subtribe Cassiinae, which may be related to an increase in the pollen-capturing surface area on the pollinator body.